Puberty occurs when areas within the brain awaken beginning a cascade of hormone signals which conclude with the gonads (ovaries and testicles) increasing their production of the female and male sex hormones estrogen and testosterone. Under the influence of these hormones a child begins the transition from childhood to sexual maturity. In boys puberty is associated with a growth spurt, the appearance of facial, axillary (arm pit) and pubic hair, acne, deepening of the voice, growth of the testicles and penis while girls undergo a growth spurt, develop breasts, acne, pubic and axillary hair, and growth of the clitoris.
Historical data shows the average age of puberty today is many years sooner than in previous generations. Most experts attribute earlier puberty to better nutrition. A recent article in metabolism.com reviewed how “over-nutrition” accelerates obese children into puberty sooner (referred to as precocious puberty) than normal weight children. The latest studies on causes of precocious puberty suggests that a child’s social environment also exerts an important influence on the timing of puberty. Researchers in Madrid publishing in The Journal of Clinical Endocrinology and Metabolism 95:4305 2010 analyzed the age of puberty in normal children, adopted children and children whose families immigrated (children not adopted but subject to high levels of personal stress) to Spain. Adopted children were 25 times more likely than other groups of children to undergo precocious puberty (breast development before the age of 8 years in girls, and boys under 9 years of age with testicular growth). Over-all girls were 11 times more likely than boys to demonstrate precocious puberty.
Researchers speculate that socio-emotional stresses early in life of children who are later adopted result in changes in the brain that cause premature maturation of vital nerve pathways. This early brain maturation later results in stimulation of the pituitary gland, turning on the hormone pathways that cause puberty. This seems strange to me because various forms of deprivation in childhood can also delay puberty. For example, girls who have anorexia remain child-like in their body development and may fail to menstruate even into their late teens. A decade ago I studied hormone levels in adults during the stress of illness and surgery and found this lowered the sex hormone levels in their blood. This makes sense from an evolutionary point of view because during stressful conditions nature wisely cuts off the reproductive hormones. Why make babies if the environment is hostile in some way? Why the opposite occurs in children under stress of adoption is an interesting but unanswered question.
Gary Pepper, M.D.,