Testosterone- An overview
Testosterone is a hormone released from the testes in the male and ovaries in females and is considered both a sex hormone as well as an anabolic hormone. It is basically a form of steroid and has effects both on secondary sexual characteristics (in the male) and also helps in bone and muscle building (anabolic effect). Thus this simple hormone (chemicals released by the endocrine glands are called hormones), has dual effects in humans. In the woman, this hormone is produced in far smaller amounts than in the male (estrogen and progesterone being the chief female sex hormones).
What are the main effects of testosterone?
The main effects as we have already mentioned can be classified in to 2 main groups: the anabolic effects are seen as an increase in muscle size and strength, mainly affecting the skeletal muscles of the male. It also accelerates bone growth and maturity. The other effect of testosterone is to help in the development of the male sex organs, notably the penis and testes in the prenatal stage (during the fetal stage). Later, during puberty, testosterone helps in the development of secondary sexual characteristics, i.e. the formation of hair in the arm pits and around the pubis, as well as on the face and chest. The period of adolescence also brings about a deep voice in the male largely due to the effect on testosterone on the voice box (larynx).
Effects during the adolescent period
The prepubertal stage (just before adolescence) sees an increased level of circulating testosterone in the male and causes a spurt in growth with an increasingly adult type of odor from the growing boy, and to a lesser extent in the girl. There is also evidence of early growth of soft hair around the genitalia and face as well as the arm pits.
Effects during puberty
The most obvious signs of puberty are due to this hormone. Notably, there is growth of the male penis and testes and in the girl, it causes an increase in size of the clitoris, a small penile like structure near the vagina. On the face, besides facial hair in boys, both sexes show a tendency to form pimples (acne) on the face. On the scalp there is a tendency to lose hair, resulting in early adult type of hair loss (called alopecia). Other signs include formation of large hair on the legs and chest. The fat on the face is lost leaving a lean appearance. There is rapid growth to reach adult height toward the end of adolescence. The voice box also enlarges with a resultant deep voice in the male. The boy also develops large shoulders and a larger jaw.
In the adult
Testosterone plays a very important role in maintaining muscle mass and strength. It also helps in keeping the male energetic and active (both mentally and physically). Testosterone also helps in spermatogenesis (sperm formation) in the male. Studies have also shown a link between testosterone levels in the blood and cardiovascular health. This appears to be an indirect effect of the hormone mediated by supporting factors that help decrease the risk for coronary disease. An example is the reduction of obesity in the male with increased physical activity spurred by testosterone.
For more information see: Testosterone