<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Human penis size and can you explain it in depth? [/INST] Human penises vary in size on a number of measures, including length and circumference when flaccid and erect. Besides the natural variability of human penises in general, there are factors that lead to minor variations in a particular male, such as the level of arousal, time of day, room temperature, anxiety level, sport activity and frequency of sexual activity. Compared to other primates, including large examples such as the gorilla, the human penis is thickest, both in absolute terms and relative to the rest of the body.
Measurements vary, with studies that rely on self-measurement reporting a significantly higher average than those with a health professional measuring. As of 2015, a systematic review of 15,521 men, who were measured by health professionals rather than themselves, concluded that the average length of an erect human penis is 13.12 cm (5.17 inches) long, while the average circumference of an erect human penis is 11.66 cm (4.59 inches). Flaccid penis length can sometimes be a poor predictor of erect length.

Most human penis growth occurs between infancy and the age of five, and between about one year after the onset of puberty and, at latest, approximately 17 years of age.Limited to no statistically significant correlation between penis size and the size of other body parts has been found in research. Some environmental factors in addition to genetics, such as the presence of endocrine disruptors, can affect penis growth. An adult penis with an erect length of less than 7 cm (2.8 in), but otherwise formed normally, is referred to in medicine as a micropenis.

Studies
While results vary slightly across reputable studies, the consensus is that the mean human penis, when erect, is in the range 12.9–15 cm (5.1–5.9 in) in length.

A 2015 systematic review published by Veale et al. of medical research on the topic over the previous 30 years published in BJU International showed similar results, giving mean flaccid, stretched non-erect, and erect lengths of 9.16 cm, 13.24 cm, and 13.12 cm respectively, and mean flaccid and erect circumferences of 9.31 cm and 11.66 cm respectively. Erect lengths in the included studies were measured by pushing the pre-pubic fat pad to the bone, and flaccid or erect girth (circumference) was measured at the base or mid-shaft of the penis.

Length
Flaccid
One study (published in 1996) found the mean flaccid penis length to be 3.5 inches (8.9 cm) (measured by staff). A review of several studies found average flaccid length to be 9–10 cm (3.5–3.9 in). Length of the flaccid penis does not necessarily correspond to length of the erect penis; some smaller flaccid penises grow much longer, while some larger flaccid penises grow comparatively less.The penis and scrotum can contract involuntarily in reaction to cold temperatures, anxious or nervous level and participation in sports. This decrease of flaccid penis size is referred to by the slang term "shrinkage", due to action by the cremaster muscle. The same phenomenon affects cyclists and exercise bike users, with prolonged pressure on the perineum from the bicycle saddle and the straining of the exercise causing the penis and scrotum to contract involuntarily. An incorrect saddle may ultimately cause erectile dysfunction (see crotch pressure for more information). Individuals with hard flaccid syndrome or other pelvic floor disorders may temporarily have an abnormally small penis.

Stretched
Neither age nor size of the flaccid penis accurately predicted erectile length. Stretched length has correlated with erect length in some cases. However, studies have also shown drastic differences between stretched and erect length. One study found that a minimal tension force of approximately 450 g during stretching of the penis was required to reach a full potential erection length. this study also found that tension forces exerted in this study by the urologist were shown to be significantly (P<0.01) lower than 450g. This may account for differences between stretched and erect length.

The 2015 study of 15,521 men found that the average length of a stretched flaccid penis was 13.24 cm (5.21 inches) long, which is near identical to the average length of an erect human penis which is 13.12 cm (5.17 inches) long.
An 2001 study of about 3,300 men published in European Urology concluded that flaccid stretched length was measured on average to about 12.5 cm (4.9 in). In addition, they checked for correlations in a random subset of the sample consisting of 325 men. They found a few statistically significant Spearmans correlations: between flaccid length and height of 0.208, −0.140 with weight, and −0.238 with BMI, flaccid circumference and height 0.156, stretched length and height 0.221, weight −0.136, BMI −0.169. They also reported a few non-significant correlations.

Erect
Scientific studies have been performed on the erect length of the adult penis. Studies that have relied on self-measurement, including those from Internet surveys, consistently reported a higher average length than those that used medical or scientific methods to obtain measurements.The following staff-measured studies are composed of different subgroups of the human population (in other words, specific age range or race; selection of those with sexual medical concerns or self-selection) that could cause a sample bias.
In a study of 80 healthy males published in the September 1996 Journal of Urology an average erect penis length of 12.9 cm (5.1 in) was measured. The purpose of the study was to "provide guidelines of penile length and circumference to assist in counseling patients considering penile augmentation." Erection was pharmacologically induced in 80 physically normal American men (varying ethnicity, average age 54). It was concluded: "Neither patient age nor size of the flaccid penis accurately predicted erectile length."
A study published in the December 2000 International Journal of Impotence Research found that average erect penis length in 50 Jewish Caucasian males was 13.6 cm (5.4 in) (measured by staff). The study intended "to identify clinical and engineering parameters of the flaccid penis for prediction of penile size during erection." Erection was pharmacologically induced in 50 Jewish Caucasian patients who had been evaluated for erectile dysfunction (ED) (average age 47±14y). Patients with penis abnormalities or whose ED could be attributed to more than one psychological origin were omitted from the study.
A review published in the 2007 issue of BJU International showed the average erect penis length to be 14–16 cm (5.5–6.3 in) and girth to be 12–13 cm (4.7–5.1 in). The paper compared results of twelve studies conducted on different populations in several countries. Various methods of measurements were included in the review.
A 2015 study by BJU International concluded the average erect penis length to be 13.12 cm (5.16 inches).
A 2013 study of 253 men from Tanzania found that the average erect penis length of Tanzanian males was 13.12 cm (5.17 inches)
An Indian study (published in 2007) of 301 men ages 18 to 60 published in the International Journal of Impotence Research found flaccid, stretched and erect length to be 8.21 cm (3.23 in), 10.88 cm (4.28 in) and 13.01 cm (5.12 in), respectively.
A Korean study (published in 1971) of 702 men ages 21 to 31 identified the average erect penis length to be 12.70 cm (5.00 in). Another study (from 1998) of 150 Koreans found the average erect penis length to be 13.42 cm (5.28 in). The most recent study (published in 2016) of 248 Korean men identified the average erect penis length to be 13.53 cm (5.33 in).
A 2020 review in the Journal of Sex & Marital Therapy found that the majority of men believed that the average erect penis length is more than 15.24 cm (6 inches). This inaccurate belief has likely been fed by inaccurate and exaggerated data presented in studies where the size of the participants erect  penis is self-reported. Participants may report overestimates of the size of their penis in the belief that a larger penis is more socially desirable.  The same review analyzed the results from ten prior studies where measurements of erect penis size were made by researchers. They reported an erect penis to be between 12.95 and 13.92 cm (5.1 and 5.5 inches, respectively) in length, a result significantly below the average obtained in self-reported studies. The authors commented that results of such measurement studies may still be inflated due to volunteer bias – the possibility that men with larger penises may be more likely to choose to participate in such studies.

Erect circumference
Similar results exist regarding studies of the circumference of the adult fully erect penis, with the measurement usually taken mid-shaft. As with length, studies that relied on self-measurement consistently reported a significantly higher average than those with staff measuring. In a study of penis size where measurements were taken in a laboratory setting, the average penis circumference when erect was 11.66 cm (4.59 inches).

Size at birth
The average stretched penile length at birth is about 4 cm (1.6 in), and 90% of newborn boys will be between 2.4 and 5.5 cm (0.94 and 2.17 in). Limited growth of the penis occurs between birth and 5 years of age, but very little occurs between 5 years and the onset of puberty. The average size at the beginning of puberty is 6 cm (2.4 in) with adult size reached about 5 years later. W.A. Schonfeld published a penis growth curve in 1943.

Size with ageing
Authors of a paper reviewing research on area of penis sizes conclude that "flaccid penile length is just under 4 cm (1.6 in) at birth and changes very little until puberty, when there is marked growth."Age is not believed to negatively correlate with penis size. "Individual research studies have... suggested that penis size is smaller in studies focusing on older men, but Wylie and Eardley found no overall differences when they collated the results of various studies [over a 60 year period]."

Size and height
A 2015 review of the literature found two studies finding height and stretched or flaccid length to be moderately correlated, seven studies finding weak correlation for flaccid, stretched, or erect length, and two studies that found no correlation between flaccid length and height.

Size and hands
One study investigated the relationship with digit ratio and found that men with longer ring fingers than index fingers had slightly longer penises. However, the common misconception that hand size predicts penis size has been widely discredited.

Size and other body parts
One study, Siminoski and Bain (1988), found a weak correlation between the size of the stretched penis and foot size and height; however, it was too weak to be used as a practical estimator. Another investigation, Shah and Christopher (2002), which cited Siminoski and Bain (1988), failed to find any evidence for a link between shoe size and stretched penis size, stating "the supposed association of penile length and shoe size has no scientific basis".A study by Ikegaya et al. (2021) concluded that nose size was highly related to stretched penile length in Japanese male cadavers.There may be a link between the malformation of the genitalia and the human limbs. The development of the penis in an embryo is controlled by some of the same Hox genes (in particular HOXA13 and HOXD13) as those that control the development of the limbs. Mutations of some Hox genes that control the growth of limbs cause malformed genitalia (hand-foot-genital syndrome).

Size and race
Alleged differences in races have led to the creation of sexual myths.
A 2005 study reported that "there is no scientific background to support the alleged oversized penis in black people".A study of 253 men from Tanzania found that the average stretched flaccid penis length of Tanzanian males is 11.5 cm (4.53 inches) long, smaller than the worldwide average, stretched flaccid penis length of 13.24 cm (5.21 inches), and average erect penis length of 13.12 cm (5.17 inches).A 2016 study of 248 Korean men identified the average erect penis length to be 13.53 cm (5.33 in). A study of 115 men from Nigeria found that the average flaccid stretched penis length of Nigerian males is 13.37 cm (5.26 inches) long, which is near identical to the worldwide average, stretched flaccid penis length of 13.24 cm (5.21 inches) and average erect penis length of 13.12 cm (5.17 inches).
A 2014 American study by Herbenick et al. of 1,661 sexually active men involving Asian American, Black American, White American, Pacific Islander/Hawaiian, and Native American men, found average
racial differences in erect penile length and circumference to be generally less than one centimeter, with averages in length being: 14.14 cm (5.56 inches) for Asian Americans, 14.66 cm (5.77 inches) for Black Americans, 14.88 cm (5.85 inches) for Pacific Islanders/Hawaiians, 12.86 cm for Native Americans (5.06 inches), and 14.18 cm (5.58 inches) for White Americans (And in circumference: Asians 12.10 cm, Blacks 12.29 cm, Pacific Islanders 11.88 cm, Native Americans 11.36 cm, and Whites 12.25 cm).
A 2015 systematic review of 15,521 men found "no indications of differences in racial variability", and stated that it was not possible to draw any conclusions about size and race from the available literature and that further research needed to be conducted.According to Aaron Spitz, a urologist, many websites and studies promoting variation of penis size between races use unscientific methods of collecting information and often ignore contradictory evidence. He concludes that "when you really take a good look at the naked data, there’s not a whole lot there [showing racial variation in penis size]."

Size preferences among sexual partners
In a 1994 cover story by Psychology Today, 1,500 readers (about two-thirds women) were surveyed about male body image. Many of the women were not particularly concerned with penis size, and over 71% thought men overemphasized the importance of penis size and shape. Generally, the women polled cared more about width than men thought, and less about length than men thought, although the strength of caring for either among women showed a similar pattern.
In a small study conducted by University of Texas–Pan American and published in 2001 in BMC Womens Health, 50 undergraduate women were surveyed by two popular male athletes on campus about their perceptions of sexual satisfaction and it was concluded that the width of a penis feels better than the length of a penis, when subjects are asked to choose between the two (size was left unspecified). It was also concluded that this may show that penis size overall affects sexual satisfaction since women chose between the two options they were given.A study published in 2002, conducted at Groningen University Hospital, asked 375 sexually active women (who had recently given birth) the importance of penis size. The results showed that 21% of women felt length was important and 32% felt that girth was important.A study conducted at the Australian National University, published in early 2013, showed that penis size influences a mans sex appeal, and the taller the man, the bigger the effect. The study showed 3D computer generated images at life-size, altering the height and other physical attributes, with women typically registering preferences in under 3 seconds. A preference for taller mens larger penis size was indicated.
A US study published in 2015 of the stated preferences of a panel of 75 women using 3D-printed models as scale references showed a preferred penis length of 16 cm (6.3 inches) and a preferred circumference of 12.2 cm for long-term sexual partners, with slightly larger preferred sizes of a length of 16.3 cm (6.4 inches) and circumference of 12.7 cm for one-time sexual encounters.

According to the study, however, when asked to estimate the length of their partnerss penis, most women would say a size significantly smaller than what their partner was recorded to be. This suggests that perception of size is not entirely accurate. The visual impression of the size is not necessarily in correlation with the feeling in the vulva and vagina. A very long penis can cause dispareunia, if the man doesnt understand how to use it carefully.

Condom use
One Australian study of 184 men looked at penis length and circumference in relationship to condom breakage or slippage. 3,658 condoms were used. The study found that when used correctly, condoms had a breakage rate of 1.34% and a slippage rate of 2.05%, for a total failure rate of 3.39%. Penile dimensions did not influence slippage, although penis circumference and broken condoms were strongly correlated, with larger sizes increasing the rate of breakage.

Biochemistry
Androgens like testosterone are responsible for penis enlargement and elongation during puberty. Penis size is positively correlated with increasing testosterone levels during puberty. But after puberty, administration of testosterone does not affect penis size, and androgen deficiency in adult men only results in a small decrease in size. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are also involved in penis size, with deficiency (such as that observed in growth hormone deficiency or Laron syndrome) at critical developmental stages having the potential to result in micropenis.

Variance
Grower vs shower
A 2018 study differentiates two types of penises based on the change they experience from flaccid to erect. It distinguishes between growers and showers. Growers or penises of blood grow more than 4 cm with respect to their flaccid state, and showers or penises of meat grow less of 4 cm.

Genetics
There are certain genes, like homeobox (Hox a and d) genes, which may have a role in regulating penis size. In humans, the AR gene, located on the X chromosome at Xq11-12, may affect penis size. The SRY gene located on the Y chromosome may have a role to play. Variance in size can often be attributed to de novo mutations. Deficiency of pituitary growth hormone or gonadotropins or mild degrees of androgen insensitivity can cause small penis size in males and can be addressed with growth hormone or testosterone treatment in early childhood.

Conditions
An adult penis with an erect length of less than 7 cm or 2.76 inches but otherwise formed normally is referred to in a medical context as having the micropenis condition. The condition affects 0.6% of men. Some of the identifiable causes are deficiency of pituitary growth hormone or gonadotropins, mild degrees of androgen insensitivity, a variety of genetic syndromes and variations in certain homeobox genes. Some types of micropenis can be addressed with growth hormone or testosterone treatment in early childhood. Operations are also available to increase penis size in cases of micropenis in adults.

Environmental influence
It has been suggested that differences in penis size between individuals are caused not only by genetics, but also by environmental factors such as culture, diet and chemical or pollution exposure. Endocrine disruption resulting from chemical exposure has been linked to genital deformation in both sexes (among many other problems). Chemicals from both synthetic (e.g., pesticides, anti-bacterial triclosan, plasticizers for plastics) and natural (e.g., chemicals found in tea tree oil and lavender oil) sources have been linked to various degrees of endocrine disruption.
Both PCBs and the plasticizer DEHP have been associated with smaller penis size. DEHP metabolites measured from the urine of pregnant women have been significantly associated with the decreased penis width, shorter anogenital distance and the incomplete descent of testicles of their newborn sons, replicating effects identified in animals. According to a 2008 study published by the US National Library of Medicine, approximately 25% of US women have phthalate levels similar to those observed in animals.A 2007 study by the University of Ankara, Faculty of Medicine found that penile size may decrease as a result of some hormonal therapy combined with external beam radiation therapy. In addition, some estrogen-based fertility drugs like diethylstilbestrol (DES) have been linked to genital abnormalities or a smaller than normal penis (microphallus).A 2016 Korean study found that newborn male circumcision is associated with shorter penile length.

Historical perceptions
Prehistory
Perceptions of penis size are culture-specific. Some prehistoric sculptures and petroglyphs depict male figures with exaggerated erect penises. Ancient Egyptian cultural and artistic conventions generally prevented large penises from being shown in art, as they were considered obscene, but the scruffy, balding male figures in the Turin Erotic Papyrus are shown with exaggeratedly large genitals. The Egyptian god Geb is sometimes shown with a massive erect penis and the god Min is almost always shown with an erection.

Ancient
The ancient Greeks believed that small penises were ideal. Scholars believe that most ancient Greeks probably had roughly the same size penises as most other Europeans, but Greek artistic portrayals of handsome youths show them with inordinately small, uncircumcised penises with disproportionately large foreskins, indicating that these were seen as ideal. Large penises in Greek art are reserved exclusively for comically grotesque figures, such as satyrs, a class of hideous, horse-like woodland spirits, who are shown in Greek art with absurdly massive penises. Actors portraying male characters in ancient Greek comedy wore enormous, fake, red penises, which dangled underneath their costumes; these were intended as ridiculous and were meant to be laughed at.In Aristophaness comedy The Clouds, "Mr. Good Reason" gives the character Pheidippides a description of the ideal youth: "A glistening chest and glowing skin / Broad shoulders, a small tongue /A mighty bottom and a tiny prong." In Greek mythology, Priapus, the god of fertility, had an impossibly large penis that was always permanently erect. Priapus was widely seen as hideous and unattractive. A scholion on Apollonius of Rhodess Argonautica states that, when Priapuss mother Aphrodite, the goddess of love and beauty, gave birth to him, she was so horrified by the size of his penis, his massive potbelly, and his huge tongue that she abandoned him to die in the wilderness. A herdsman found him and raised him as his son, later discovering that Priapus could use his massive penis to aid in the growth of plants.Nonetheless, there are indications that the Greeks had an open mind about large penises. A statue of the god Hermes with an exaggerated penis stood outside the main gate of Athens and in Alexandria in 275 BC, a procession in honor of Dionysus hauled a 180-foot phallus through the city and people venerated it by singing hymns and reciting poems. The Romans, in contrast to the Greeks, seem to have admired large penises and large numbers of large phalli have been recovered from the ruins of Pompeii. Depictions of Priapus were very popular in Roman erotic art and literature. Over eighty obscene poems dedicated to him have survived.Penis size is alluded to in the Bible:

18 And she revealed her whorings, and she revealed her nakedness, and so I turned from her just as I turned from her sister.  19 Yet she increased her whorings, recalling the days of her childhood when she was prostituted in the land of Egypt.  20 And she lusted after her male lovers whose genitalia were the genitalia of male donkeys and their seminal emission was the seminal emission of horses. Ezekiel 23:18-20 Lexham English Bible

Ancient Chinese legend holds that a man named Lao Ai had the largest penis in history and that he had an affair with Queen Dowager Zhao (c. 280–228 BC), the mother of Qin Shi Huang, by pretending to be a eunuch. Ancient Koreans admired large penises and King Jijeung (437–514 AD) of the Silla Dynasty is said to have had a forty-five-centimeter penis that was so large his subordinates had to search for a woman that fit him. Traditional Japanese erotic paintings usually show genitals as exaggeratedly large. The oldest known painting of this type, found in the Hōryū-ji Temple in Ikaruga, dates to the eighth century AD and depicts a fairly large penis.The ancient Indian sexual treatise Kama Sutra, originally written in Sanskrit, probably between the second and fourth centuries AD, divides men into three classes based on penis size: "hare" size (about 5–7 cm, or 2–3 inches, when erect), "bull" size (10–15 cm, or 4–6 inches), and "horse" size (18–20 cm, or 7–8 inches). The treatise also divides womens vaginas into three sizes ("deer", "mare", and "elephant") and advises that a man match the size of the vagina of the woman he is having sex with to the size of his own penis. It also gives medically dubious advice on how to enlarge ones penis using wasp stings.

Postclassical
In medieval Arabic literature, a longer penis was preferred, as described in an Arabian Nights tale called "Ali with the Large Member". As a witty satire of this fantasy, the 9th-century Afro-Arab author Al-Jahiz wrote: "If the length of the penis were a sign of honor, then the mule would belong to the Quraysh" (the tribe to which Muhammad belonged and from which he descended).The medieval Norsemen considered the size of a mans penis as the measure of his manliness, and a thirteenth-century Norse magic talisman from Bergen, a wooden stave inscribed with writing in runic script, promises its wearer: "You will fuck Rannveig the Red. It will be bigger than a mans prick and smaller than a horses prick." A late fourteenth century account of the life of Saint Óláfr from the Flateyjarbók describes a pagan ritual which centered around a preserved horses penis used as a cult artifact which members of the cult would pass around in a circle, making up verses in praise of it, encouraging it and the other members of the group to behave in sexually suggestive ways.During the Renaissance, some men in Europe began to wear codpieces, which accentuated their genitals. There is no direct evidence that it was necessarily worn to enhance the apparent size of the wearers penis, but larger codpieces were seen as more fashionable.

Contemporary perceptions
Male self-perception
Males may quite easily underestimate the size of their own penis relative to those of others. A survey by sexologists showed that many men who believed that their penis was of inadequate size had average-sized penises. Another study found sex education of standard penile measurements to be helpful and relieving for patients concerned about small penis size, most of whom had incorrect beliefs of what is considered medically normal. The study found that almost all of their patients that were concerned about their penis size overestimated the average penis size. The perception of having a large penis is often linked to higher self-esteem. Fears of shrinking of the penis in folklore have led to a type of mass hysteria called penis panic, though the penis legitimately can shrink in size due to scar tissue formation in the penis from a medical condition called Peyronies disease. Marketers of penis enlargement products exploit fears of inadequacy, but there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range.

Shrinking and enlarging
Widespread private concerns related to penis size have led to a number of folklore sayings and popular culture reflections related to penis size. Penis panic is a form of mass hysteria involving the believed removal or shrinking of the penis, known as genital retraction syndrome. The penis can significantly shrink due to scar tissue formation from a condition called Peyronies disease which affects up to 10% of men. Products such as penis pumps, pills, and other dubious means of penis enlargement are some of the most marketed products in email spam. At present there is no consensus in the scientific community of any non-surgical technique that permanently increases either the thickness or length of the erect penis that already falls into the normal range (4.5" to 7").

Among male homosexuals
A study undertaken at Utrecht University found that the majority of gay men in the study regarded a large penis as ideal, and having one was linked to self-esteem. One study analysing the self-reported Kinsey data set found that the average penis of a homosexual man was larger than the average penis of their heterosexual counterparts (6.32 inches [16.05 cm] in length amongst gay men versus 5.99 in [15.21 cm] in heterosexuals, and 4.95 inches [12.57 cm] circumference amongst gay men versus 4.80 in [12.19 cm] in heterosexual men).

Evolution
The human penis is thicker than that of any other primate, both in absolute terms and relative to the rest of the body. Early research, based on inaccurate measurements, concluded that the human penis was also longer. In fact, the penis of the common chimpanzee is no shorter than in humans, averaging 14.4 cm (5.7 inches), and some other primates have comparable penis sizes relative to their body weight.The evolutionary reasons for the increased thickness have not been established. One explanation is that thicker penises are an adaptation to a corresponding increase in vaginal size. The vaginal canal is believed to have expanded in humans to accommodate the larger size of a newborns skull. Women may then have sexually selected men with penises large enough to fit their vagina, to provide sexual stimulation and ensure ejaculation.Other evolutionary hypotheses to explain humans relatively large penis length and girth include a sperm competition hypothesis and a mate competition hypothesis. The sperm competition hypothesis does not have much support as in other mammals where sperm competition is present, larger testes evolve, not larger penises. The mate competition hypothesis involves the prediction that a human with a larger penis would be able to displace the sperm of another. Studies have found that larger penises do not displace other sperm more effectively than smaller penises, but rather longer penises may ejaculate sperm inside the vagina in places that would be harder for a following penis to displace. The depth of pelvic thrusting was correlated to the displacement of competing sperm.

See also
Digit ratio
Human vaginal size
Jonah Falcon
Penis enlargement
Penis envy
Phalloplasty
Sexual selection in humans
The Third Chimpanzee
Why Is Sex Fun?

References
Citations
General and cited sources
"Men worry more about penile size than women, says 60-year-old research review" (Press release). Blackwell. 31 May 2007. Retrieved 11 August 2018.
Lee, P. A; Mazur, T; Danish, R; Amrhein, J; Blizzard, R. M; Money, J; Migeon, C. J (1980). "Micropenis. I. Criteria, etiologies and classification". The Johns Hopkins Medical Journal. 146 (4): 156–63. PMID 7366061. NAID 10010056499.
Lauersen, Niels; Whitney, Steven (1983). Its Your Body: A Womans Guide to Gynecology (3rd ed.). New York: Berkley Publishing. p. 480 </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Occlusal trauma and can you explain it in depth? [/INST] Occlusal trauma is the damage to teeth when an excessive force is acted upon them and they do not align properly.When the jaws close, for instance during chewing or at rest, the relationship between the opposing teeth is referred to as occlusion. When trauma, disease or dental treatment alters occlusion by changing the biting surface of any of the teeth, the teeth will come together differently, and their occlusion will change. When that change has a negative effect on how the teeth occlude, this may cause tenderness, pain, and damage to or movement of the teeth. This is called traumatic occlusion.Traumatic occlusion may cause a thickening of the cervical margin of the alveolar bone and widening of the periodontal ligament, although the latter can also be caused by other processes.

Signs and symptoms
Clinically, there is a number of physiological results that serve as evidence of occlusal trauma:,
Progressive Tooth mobility
Fremitus
Tooth migration
Pain
Thermal sensitivity
Pain on chewing or percussion
Wear facets

Diagnosis
Microscopically, there will be a number of features that accompany occlusal trauma:
Hemorrhage
Necrosis
Widening of the periodontal ligament, or PDL (also serves as a very common radiographic feature)
Bone resorption
Cementum loss and tearsIt was concluded that widening of the periodontal ligament was a "functional adaptation to changes in functional requirements".

Primary vs. secondary
There are two types of occlusal trauma, primary and secondary.

Primary
Primary occlusal trauma occurs when greater than normal occlusal forces are placed on teeth, as in the case of parafunctional habits, such as bruxism or various chewing or biting habits, including but not limited to those involving fingernails and pencils or pens.
The associated excessive forces can be grouped into three categories.  Excesses of:
Duration
Frequency and
MagnitudePrimary occlusal trauma will occur when there is a normal periodontal attachment apparatus and, thus, no periodontal disease.

Secondary
Secondary occlusal trauma occurs when normal or excessive occlusal forces are placed on teeth with compromised periodontal attachment, thus contributing harm to an already damaged system.  As stated, secondary occlusal trauma occurs when there is a compromised periodontal attachment and, thus, a pre-existing periodontal condition.

Cause and treatment
Teeth are constantly subject to both horizontal and vertical occlusal forces </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Linear verrucous epidermal nevus and can you explain it in depth? [/INST]  </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Bálints syndrome and can you explain it in depth? [/INST] Bálints syndrome is an uncommon and incompletely understood triad of severe neuropsychological impairments: inability to perceive the visual field as a whole (simultanagnosia), difficulty in fixating the eyes (oculomotor apraxia), and inability to move the hand to a specific object by using vision (optic ataxia). It was named in 1909 for the Austro-Hungarian neurologist and psychiatrist Rezső Bálint who first identified it.Bálints syndrome occurs most often with an acute onset as a consequence of two or more strokes at more or less the same place in each hemisphere. Therefore, it occurs rarely. The most frequent cause of complete Bálints syndrome is said by some to be sudden and severe hypotension, resulting in bilateral borderzone infarction in the occipito-parietal region. More rarely, cases of progressive Bálints syndrome have been found in degenerative disorders such as Alzheimers disease or certain other traumatic brain injuries at the border of the parietal and the occipital lobes of the brain.
Lack of awareness of this syndrome may lead to a misdiagnosis and resulting inappropriate or inadequate treatment. Therefore, clinicians should be familiar with Bálints syndrome and its various etiologies.

Presentation
Bálints syndrome symptoms can be quite debilitating since they impact visuospatial skills, visual scanning and attentional mechanisms. Since it represents impairment of both visual and language functions, it is a significant disability that can affect the patients safety—even in ones own home environment, and can render the person incapable of maintaining employment. In many cases the complete trio of symptoms—inability to perceive the visual field as a whole (simultanagnosia), difficulty in fixating the eyes (oculomotor apraxia), and inability to move the hand to a specific object by using vision (optic ataxia)—may not be noticed until the patient is in rehabilitation. Therapists unfamiliar with Bálints syndrome may misdiagnose a patients inability to meet progress expectations in any of these symptom areas as simply indicating incapability of benefiting from further traditional therapy. The very nature of each Bálint symptom frustrates rehabilitation progress in each of the other symptoms. Much more research is needed to develop therapeutic protocols that address Bálint symptoms as a group since the disabilities are so intertwined.

Simultanagnosia
Simultanagnosia is the inability to perceive simultaneous events or objects in ones visual field. People with Bálints syndrome perceive the world erratically, as a series of single objects rather than seeing the wholeness of a scene.This spatial disorder of visual attention—the ability to identify local elements of a scene, but not the global whole—has been referred to as a constriction of the individuals global gestalt window—their visual "window" of attention. People fixate their eyes to specific images in social scenes because they are informative to the meaning of the scene. Any forthcoming recovery in simultanagnosia may be related to somehow expanding the restricted attentional window that characterizes this disorder.Simultanagnosia is a profound visual deficit. It impairs the ability to perceive multiple items in a visual display, while preserving the ability to recognize single objects. One study suggests that simultanagnosia  may result from an extreme form of competition between objects which makes it difficult for attention to be disengaged from an object once it has been selected. Patients with simultanagnosia have a restricted spatial window of visual attention and cannot see more than one object at a time. They see their world in a patchy, spotty manner. Therefore, they pick out a single object, or even components of an individual object, without being able to see the global "big picture."A study which directly tested the relationship between the restriction of the attentional window in simultanagnosia compared with the vision of healthy participants with normal limits of visual processing confirmed the limitations of difficulties of patients with simultanagnosia.There is considerable evidence that a persons cortex is essentially divided into two functional streams: an occipital-parietal-frontal pathway that processes "where" information and an occipital-temporal-frontal pathway that provides "what" information to the individual.

Oculomotor apraxia
Bálint referred to this as "psychic paralysis of gaze"—the inability to voluntarily guide eye movements, changing to a new location of visual fixation. A major symptom of Oculomotor apraxia is that a person has no control over their eye movements, however, vertical eye movements are typically unaffected. For example, they often have difficulty moving their eyes in the desired direction. In other words, the saccades (rapid eye movements) are abnormal. Because of this, most patients with Oculomotor apraxia have to turn their heads in order to follow objects coming from their peripherals.

Optic ataxia
Optic ataxia is the inability to guide the hand toward an object using visual information where the inability cannot be explained by motor, somatosensory, visual field deficits or acuity deficits. Optic ataxia is seen in Bálints syndrome where it is characterized by an impaired visual control of the direction of arm-reaching to a visual target, accompanied by defective hand orientation and grip formation. It is considered a specific visuomotor disorder, independent of visual space misperception.Optic ataxia is also known as misreaching or dysmetria (English: difficult to measure), secondary to visual perceptual deficits. A patient with Bálints syndrome likely has defective hand movements under visual guidance, despite normal limb strength. The patient is unable to grab an object while looking at the object, due to a discoordination of eye and hand movement. It is especially true with their contralesional hand.Dysmetria refers to a lack of coordination of movement, typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye. It is sometimes described as an inability to judge distance or scale.
As Bálint states, optic ataxia impaired his patients daily activities, since, while cutting a slice of meat...which he held with a fork in his left hand, ...would search for it outside the plate with the knife in his right hand, or ...while lighting a cigarette he often lit the middle and not the end. Bálint pointed out the systematic nature of this disorder, which was evident in the patients behaviour when searching in space. Thus, when asked to grasp a presented object with his right hand, he would miss it regularly, and would find it only when his hand knocked against it.
The reaching ability of the patient is also altered. It takes them longer to reach toward an object. Their ability to grasp an object is also impaired. The patients performance is even more severely deteriorated when vision of either the hand or the target is prevented.

Cause
The visual difficulties in Bálints syndrome are usually due to damage to the parieto-occipital lobes on both sides of the brain. The parietal lobe is the middle area of the top part of the brain and the occipital lobe is the back part of the brain. (It usually does not affect the temporal lobes)

Diagnosis
Lack of awareness of the syndrome may lead to misdiagnosis such as blindness, psychosis, or dementia. Symptoms of Bálints syndrome are most likely to be noticed first by optometrtists or ophthalmologists during an eye check up, or therapists providing rehabilitation following brain lesions. However, due to the scarcity among practitioners of familiarity with the syndrome, the symptoms are often explained away incorrectly without being considered as a possibility and followed by medical confirmation of clinical and neuroradiological findings. Any severe disturbance of space representation, spontaneously appearing following bilateral parietal damage, strongly suggests the presence of Bálints syndrome and should be investigated as such. One study reports that damage to the bilateral dorsal occipitoparietal regions appeared to be involved in Bálints syndrome.

Neuroanatomical evidence
Bálints syndrome has been found in patients with bilateral damage to the posterior parietal cortex. The primary cause of the damage and the syndrome can originate from multiple strokes, Alzheimers disease, intracranial tumors, or brain injury. Progressive multifocal leukoencephalopathy and Creutzfeldt–Jakob disease have also been found to cause this kind of damage. This syndrome is caused by damage to the posterior superior watershed areas, also known as  the parietal-occipital vascular border zone (Brodmanns areas 19 and 7).

Manifestations
Some telltale signs suggesting Bálints syndrome following bilateral brain insults may include:
limitation to perceive only stimuli that is presented at 35 to 40 degrees to the right. They are able to move their eyes but cannot fixate on specific visual stimuli (optic apraxia).
patients field of attention is limited to one object at a time. making activities like reading difficult because each letter is perceived separately (simultanagnosia).
figure/ground defects in which a patient can see either the background but not the object residing somewhere in the whole scene, or conversely can see the object but sees no background around it (simultanagnosia)
a patient, while attempting to put one foot into a slipper by trying to insert the foot into a nonexistent slipper several inches from the real slipper, even as the patient focuses on the actual slipper (optic ataxia)
a patient raising a fork or spoon containing food to a point on the patients face above or below the mouth, and possibly finding the mouth by trial and error by manually moving the utensil on the face (optic ataxia)

Treatment
In terms of the specific rehabilitation of visuoperceptual disorders such as Bálints syndrome, the literature is extremely sparse. According to one study, rehabilitation training should focus on the improvement of visual scanning, the development of visually guided manual movements, and the improvement of the integration of visual elements. Very few treatment strategies have been proposed, and some of those have been criticized as being poorly developed and evaluated.Three approaches to rehabilitation of perceptual deficits, such as those seen in Bálints syndrome, have been identified:

The adaptive (functional) approach, which involves functional tasks utilising the persons strengths and abilities, helping them to compensate for problems or altering the environment to lessen their disabilities. This is the most popular approach.
The remedial approach, which involves restoration of the damaged CNS by training in the perceptual skills, which may be generalised across all activities of daily living. This could be achieved by tabletop activities or sensorimotor exercises.
The multicontext approach, which is based on the fact that learning is not automatically transferred from one situation to another. This involves practicing of a targeted strategy in a multiple environment with varied tasks and movement demands, and it incorporates self-awareness tasks.

Case studies
Symptoms of Bálints syndrome were found in the case of a 29-year-old with migraines. In the aura before the migraine headache, she experienced an inability to see all of the objects in the visual field simultaneously; an inability to coordinate hand and eye movements; and an inability to look at an object on command. Symptoms were not present before the onset of the migraine or after it passed.A study of a patient with Corticobasal Ganglionic Degeneration (CGBD) also showed a development of Bálints syndrome. As a result of CGBD, the patient developed an inability to move his eyes to specific visual objects in his peripheral fields. He also was unable to reach out and touch objects in his peripheral fields. An inability to recognize more than one item at a time was also experienced when presented with the Cookie Theft Picture from the Boston Diagnostic Aphasia Examination.A 58-year-old male presented with Bálints syndrome secondary to severe traumatic brain injury 4-months post-injury onset. He had completed a comprehensive post-acute brain injury rehabilitation program. He received 6 months of rehabilitation services as an inpatient </s>


<s> [INST] <<SYS>> You are a responsible assistant committed to providing accurate and helpful responses. Avoid sharing harmful or biased content. Clarify any unclear or incorrect questions rather than providing false or misleading information. <</SYS>> What is Hemiballismus and can you explain it in depth? [/INST] Hemiballismus or hemiballism is a basal ganglia syndrome resulting from damage to the subthalamic nucleus in the basal ganglia. Hemiballismus is a rare hyperkinetic movement disorder, that is characterized by violent involuntary limb movements, on one side of the body, and can cause significant disability. Ballismus affects both sides of the body and is much rarer. Symptoms can decrease during sleep.Hemiballismus differs from chorea in that the movements occur in the proximal limbs whereas in chorea the limb movements are in the distal limbs. Also in chorea the movements are more dance-like, flowing from one region to another.

Presentation
Ballism was defined by Meyers in 1968 as "Repetitive, but constantly varying, large amplitude involuntary movements of the proximal parts of the limbs. This activity is almost ceaseless and movements are often complex and combined". Hemiballismus is usually characterized by involuntary flinging motions of the extremities. The movements are often violent and have wide amplitudes of motion. They are continuous and random and can involve proximal or distal muscles on one side of the body. Some cases even include the facial muscles. It is common for arms and legs to move together. The more a patient is active, the more the movements increase. With relaxation comes a decrease in movements. Physicians can measure the severity of the disorder by having the patient perform a series of basic, predetermined tasks and counting the hemiballistic movements during a set time session. The physicians then rate the patient on a severity scale. This scale gives scientists and clinicians a way to compare patients and determine the range of the disorder.The name hemiballismus literally means "half ballistic", referring to the violent, flailing movements observed on one side of the body.

Causes
In examining the causes of hemiballismus, it is important to remember that this disorder is extremely rare. While hemiballismus can result from the following list, just because a patient has one of these disorders does not mean they will also experience hemiballismus.

Stroke
Hemisballismus as a result of stroke occurs in only about 0.45 cases per hundred thousand stroke patients. Even at such a small rate, stroke is by far the most common cause of hemiballismus. A stroke causes tissue to die due to a lack of oxygen resulting from an impaired blood supply. In the basal ganglia, this can result in the death of tissue that helps to control movement. As a result, the brain is left with damaged tissue that sends damaged signals to the skeletal muscles in the body. The result is occasionally a patient with hemiballismus.

Traumatic brain injury
Hemiballismus can also occur as a result of a traumatic brain injury. There are cases in which survivors of assault or other forms of violence have developed hemiballismus. Through these acts of violence, the survivors brain has been damaged and the hemiballistic movements have developed.

Amyotrophic lateral sclerosis
This disease causes neuronal loss and gliosis, which can include the subthalamic nucleus and other areas of the brain. Essentially any disorder that causes some form of neuronal loss or gliosis in the basal ganglia has the potential to cause hemiballismus.

Nonketotic hyperglycemia
Patients with nonketotic hyperglycemia can develop hemiballismus as a complication to the disease through the development of a subthalamic nucleus lesion. This is the second most common reported cause of hemiballismus. It can be found primarily in the elderly and many of the reported cases have come from East Asian origin, which suggests that there may be some genetic disposition to development of hemiballismus as a result of hyperglycemia. Hemiballistic movements appear when blood glucose levels get too high and then subside once glucose levels return to normal. This time scale for this is usually several hours. In patients with this type of hemiballismus, imaging reveals abnormalities in the putamen contralateral to the movements as well as the globus pallidus and caudate nucleus. While the hyperglycemia itself is not the cause of the hemiballistic movements, it has been suggested that petechial hemorrhage or a decreased production of GABA and acetylcholine could result secondary to the hyperglycemia. One of these issues could be responsible for the hemiballistic movements.

Neoplasms
A neoplasm is an abnormal growth of cells. Cases have shown that if this occurs somewhere in the basal ganglia, hemiballismus can result.

Vascular malformations
Vascular malformations can cause abnormal blood flow to areas of the brain. If too little blood is delivered to the basal ganglia, a stroke can occur.

Tuberculomas
This is another form of tumor that can result in the brain as a result of a tuberculous meningitis infection. This type of tumor can also damage parts of the basal ganglia, sometimes resulting in hemiballismus.

Demyelinating plaques
Demyelinating plaques attack the myelin sheaths on neurons. This decreases the conduction velocity of the neurons, making the signals received by the basal ganglia garbled and incomplete. This disorganized signal can also cause the chaotic movements characterized by hemiballismus.

Complications from HIV infection
Patients with HIV often have complications that arise along with AIDS. Hypoglycemia due to pentamidine use in patients with AIDS has been known to cause hemiballismus. In some patients, hemiballismus has been the only visible symptom to alert the physician that the patients may have AIDS. It is typically a result of a secondary infection that occurs due to the compromised immune system and the most common infection causing hemiballismus is cerebral toxoplasmosis. Most of the lesions that result from this infection are found in the basal ganglia. As long as the diagnosis is not missed, this type of hemiballismus can be treated just as well as in patients without HIV.

Anatomy
Basal ganglia
The basal ganglia are a collection of nuclei that connects to several other areas of the brain. Due to the diverse nuclei that they contain, the basal ganglia are involved in numerous functions, including motor control. It is within this structure that hemiballismus primarily occurs in the brain.

Subthalamic nucleus
This structure within the basal ganglia innervates other structures, including a very important connection to the internal globus pallidus. The subthalamic nucleus essentially provides the excitement needed to drive the globus pallidus. Injury to this area or its efferent or afferent connections can induce this disorder contralateral to the side of the lesion. The structure itself is a regulator of motor function and is also involved in associative and limbic functions. It was traditionally thought that the disorder was only caused by injury to the subthalamic nucleus, but later studies have shown that damage to other basal ganglia regions can also be responsible for causing this disorder. Hemiballismus caused by lesions in the subthalamic nucleus is more severe than other forms of the disorder.

Globus pallidus
From recent studies, it is now thought that hemiballismus can be associated with a decreased output of the globus pallidus. This is because studies have shown that firing rates decrease from 70/s to 40/s. In addition to a decreased firing rate, degenerative neurological disorders that cause patients to exhibit hemiballistic movements show a marked decrease in the globus pallidus mass as well. Increases in activity in this area causes there to be an inhibition of the motor thalamus. This causes cortical activation and thus a movement inhibition. In the case of hemiballismus, the opposite occurs, leading to the characteristic large, irregular movements.

Putamen
The putamen is also part of the basal ganglia and can be involved in hemiballismus due to the fact that it projects to the premotor cortex through the globus pallidus. As a result, damage to this area can also cause hemiballistic movements to be seen as it is also part of the chain in movement.

Caudate nucleus
The caudate nucleus is the portion of the basal ganglia that helps control voluntary movement.  Damage to this area can also result in hemiballismus as it is directly related to voluntary movement.

Cortical structures
While the majority of damage that causes hemiballismus occurs within the basal ganglia, there are still cases that have been documented on which damage to cortical structures has caused hemiballistic movements.

Diagnosis
Diagnosis of hemiballismus is a clinical one, made with observation during clinical examination. Hemiballismus is a clinical sign with a number of different causes. Therefore, a diagnosis underlying this clinical sign should be sought. The observer should note sudden, flinging movements of a limb(s) and occasionally the face. This is commonly unilateral ("Hemiballismus"). The movements must be distinguished from other hyperkinetic movement disorders such as tremor (generally more rhythmic, and smaller amplitude) and chorea, akathisia and athetosis (all are often of lower amplitude and less violent).

Treatments
When treating hemiballismus, it is first important to treat whatever may be causing the manifestation of this disorder. This could be hyperglycemia, infections, or neoplastic lesions. Some patients may not even need treatment because the disorder is not severe and can be self-limited.

Dopamine blockers
When pharmacological treatment is necessary, the most standard type of drug to use is an antidopaminergic drug. Blocking dopamine is effective in about ninety percent of patients. Perphenazine, pimozide, haloperidol, and chlorpromazine are standard choices for treatment. Scientists are still unsure as to why this form of treatment works, as dopamine has not been directly linked to hemiballismus.

Anticonvulsants
An anticonvulsant called topiramate has helped patients in three cases and may be a viable treatment for the future.

ITB therapy
Intrathecal baclofen (ITB) therapy is used to treat a variety of movement disorders such as cerebral palsy and multiple sclerosis. It can also be a possibility to help treat hemiballismus. In one case, before ITB the patient had an average of 10–12 ballism episodes of the right lower limb per hour. During episodes, the right hip would flex up to about 90 degrees, with a fully extended knee. After an ITB pump was implanted and the correct dosage was found, the frequency of ballistic right leg movements decreased to about three per day, and the right hip flexed to only 30 degrees. The patient was also able to better isolate individual distal joint movements in the right lower limb. The patient currently receives 202.4 microg/day of ITB and continues to benefit almost 6 years after the ITB pump was implanted.

Botulinum injections
New uses for botulinum toxin have included treatment of hemiballismus. However, this is still in the early stages of testing. This treatment deals with the muscular manifestations of hemiballismus as opposed to the neurological causes.

Tetrabenazine
Tetrabenazine has been used to treat other movement disorders, but is now being used to treat hemiballismus. Patients using this medication have had a dramatic response. However, lowering the dosage leads to a return of symptoms. This drug works by depleting dopamine.

Antipsychotics
In one case, a patient had not been responding to haloperidol, thus the physician tried olanzapine. The patient made a significant recovery. More research is being performed on the use of these types of drugs in treating hemiballismus.

Functional neurosurgery
Surgery as a treatment should only be used on patients with severe hemiballismus that has not responded to treatment. Lesioning of the globus pallidus or deep brain stimulation of the globus pallidus are procedures that can be used on humans. Usually, lesioning is favored over deep brain stimulation because of the maintenance required to continue stimulating the brain correctly and effectively.

Prognosis
In the past, the prognosis for patients with this disease had been very poor; with many patients experiencing severe disability or death. Now, patients are responding remarkably well to current treatments and the majority of patients go into spontaneous remission. For those that do not go into remission, the symptoms of hemiballismus can generally be very well controlled with medication.
Due to the rarity of this disorder, scientists know very little about the details of hemiballismus.

There appears to be a discrepancy between this disorder in humans and animals that has yet to be explained.
Hemiballismus can also be induced by damage to other areas of the basal ganglia besides the subthalamic nucleus. Research is being done in these areas in order to give scientists and clinicians a better model for this disease that will ultimately lead to better diagnosis and treatment of this disorder.
Research is also being done on why certain treatments seem to help hemiballistic patients when they should seemingly do more harm. An example of this is why lesioning the globus pallidus seems to reduce hemiballistic movements.
The mechanism behind the effect of dopamine on patients symptoms remains unknown.

History
The work of J.R. Whittier, F.A.  Mettler, and M.B. Carpenter in the mid-1900s helped scientists and clinicians form a more complete picture of hemiballismus. In their experiments, several lesions were made in the basal ganglia structures in monkeys and then they monitored the results. They noticed that the majority of the time, the monkeys did not have any unusual movements </s>