|MadSci Network: Development|
Brandon and classmates: As boys and girls get older, many changes take place in their bodies. At about 12-14 years of age, boys and girls begin the process called puberty. During puberty there are increases in chemicals called hormones in the blood. In boys, the hormone testosterone increases dramatically. Among other jobs, testosterone stimulates hair growth on the face, under the arms and near the sexual organs. The age when hair growth occurs varies with each person and some young men do not get facial hair until they are in their twenties. In girls, there is very little change in testosterone, but a large change in estrogen. This hormone causes increases in body hair, but does not cause facial hair because the hair follicles on the face are not capable of seeing the estrogen (no estrogen receptor). If girls are exposed to the male hormone testosterone, they too can grow facial hair. There are many ideas about why males grow facial hair and females do not. It may be a display of the maturity of the individual. This is similar to the change in color that chicks undergo as they become more mature. Thanks for your question. David Mallory, PhD Marshall University Huntington WV
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