What does the thyroid gland do?
The thyroid gland is an endocrine gland located at the base of your neck that regulates metabolism or how your body uses energy, which in turn affects breathing, heart rate, body weight, menstrual cycles, body temperature, cholesterol levels, and other functions. This gland uses iodine from the foods we eat to form triiodothyronine (T3) and thyroxine (T4). The hypothalamus in the brain senses how much T3 and T4 is in the blood (see diagram above):
- When levels of T3/T4 are low, the hypothalamus secretes thyroid-releasing hormone (TRH) to stimulate the pituitary gland to release thyroid stimulating hormone (TSH), which then stimulates the thyroid gland to produce more T3 and T4 in a ratio of approximately 1:4
- When levels of T3/T4 are high, the hypothalamus stops secreting thyroid-releasing hormone (TRH) to inhibit the pituitary gland from release thyroid stimulating hormone (TSH), which then reduces the amount of T3 and T4 produced by the thyroid gland
T4 is considered a prohormone because it is not active and needs to be converted to T3, which occurs throughout the body by two enzymes called type 1 and type 2 deiodinases (D1 and D2). D1 is expressed primarily in the liver and kidneys (and to a lesser extent the thyroid gland), whereas D2 is expressed primarily in the central nervous system, pituitary gland, thyroid gland, heart, brown adipose tissue, and skeletal muscle. Approximately 24% of circulating T3 originates from the D1 pathway, whereas 60% originates from the D2 pathway.
What causes hypothyroidism?
Women are much more likely to have hypothyroidism and the incidence increases with age. There are a number of causes including:
- Hashimoto’s disease, an autoimmune disorder where your own immune system mistakes the thyroid gland cells as an invading infection and attacks them;
- Thyroiditis, which is inflammation of the thyroid gland and can happen as a result of viral infection;
- Surgical removal of the thyroid gland for conditions such as thyroid cancer or Graves’ disease;
- Prior radiation treatment to the neck or thyroid gland, which can happen with Graves’ disease;
- Medications such as amiodarone, lithium, interferon alpha, and interleukin-2;
- Damage to the pituitary gland.
What are the signs and symptoms of hypothyroidism?
- Trouble sleeping
- Difficulty concentrating
- Dry skin and hair
- Depressed mood and depression
- Cold sensitivity
- Irregular or heavy periods
- Joint and muscle pain
- Weight gain
How do I know if I have hypothyroidism?
It is important to understand that unlike the supplementation of hormones like testosterone and estrogen, hypothyroidism is diagnosed based on lab values, not symptoms. Hypothyroidism is diagnosed based on a high TSH and normal or low T4. Looking at the diagram above, the high TSH indicates that the pituitary is signaling the thyroid gland to produce more T3 and T4, yet the thyroid gland is unable to increase production. Symptoms are not used to determine if a patient is hypothyroid, although providers should be following symptoms when a patient is being treated for hypothyroidism with supplementation.
Read more about thyroid function tests: https://www.thyroid.org/thyroid-function-tests/
What treatments are available for hypothyroidism?
Levothyroxine is recommended as the first line treatment of hypothyroidism because of its efficacy in resolving the symptoms, long-term experience of its benefits, favorable side effect profile, ease of administration, good intestinal absorption, long serum half-life, and low cost. This is a synthetic form of T4, the prohormone that is converted into T3 throughout the body.
The primary goals of thyroid replacement therapy are:
- Resolution of symptoms;
- Normalization of serum TSH with improvement in thyroid hormone concentrations (T3 and T4);
- Avoid overtreatment (also known as iatrogenic thyrotoxicosis).
The diagnosis of hypothyroidism is not based on T3. In general, when a patient has normal TSH and T4 but low T3, they should not be supplemented with thyroid medication. When a patient with isolated low T3 is treated with thyroid medication, particularly medications that include T3, this can result in the patient experiencing symptoms of hyperthyroidism such as nervousness or anxiety, heat intolerance, rapid heart rate, sweating, sleep problems, thinning hair, changes to the menstrual cycle, and unintentional weight loss.
NP thyroid and Armour thyroid are natural thyroid medications that include both T3 and T4, which are prepared from the dried ground thyroid glands of pigs. Neither of these medications are recommended as first line therapy for hypothyroidism. There are hundreds of high quality clinical trials looking at the efficacy and long-term safety of synthetic preparations such as levothyroxine in treating hypothyroidism. A small subset of patients with hypothyroidism have impaired conversion of T4 to T3 by the enzymes throughout the body, and these are the patients who may benefit from using a combined preparation rather than the T4 prohormone after a trial of synthetic T4 does not result in normalization of thyroid function and resolution of symptoms.
Read the Guidelines for the Treatment of Hypothyroidism: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267409/
Since iodine is needed to make T3 and T4, should I use iodine supplements?
The general population in the United States is iodine sufficient based on monitoring systems that have been in place since the early 1970’s. This is because iodine can be found in dairy products, fish and seafood, bread, iodized salt, and many multivitamin/mineral supplements. Clinical trials have shown that significantly increasing iodine intake through supplements can both stimulate and suppress thyroid hormone production in the thyroid gland in an unpredictable manner. Because of this, we do not routinely recommend patients take an iodine supplement.
There are several populations who are at risk for low iodine:
- People who do not use iodized salt
- Pregnant women
- Vegans and people who eat few or no dairy products, seafood, and eggs
Read more about iodine in the US population: https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/
The thyroid gland is an important regulator of metabolic activity in the body. Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormone, which results in symptoms such as fatigue, trouble sleeping, difficulty concentrating, depressed mood and depression, and weight gain. Hypothyroidism is diagnosed based on lab values of TSH, T4 and T3. There are several medications that can be used to treat hypothyroidism, including levothyroxine, which is a synthetic form of T4 that gets converted to T3 throughout the body.
If you think you have hypothyroidism or would like to talk to an experienced physician about thyroid supplementation, call 434-260-1667 or submit your information using our Contact Us form: