Testosterone Testosterone Testosterone is an anabolic steroid synthesized primarily by the testes in males, the ovaries in females, and adrenal glands in both sexes. At puberty, and throughout most of the reproductive years, approximately 10-20 times more testosterone is synthesized in males than in females. In males at puberty, the much higher level of testosterone is responsible for the development of male external genitalia and secondary hair patterns, stimulation of spermatogenesis, stimulation of anabolic activity leading to increased muscle mass, and behavioral changes. In pubescent females, testosterone effects are more subtle but equally important for proper musculo-skeletal development, general anabolic activity, and libido. In both sexes, testosterone enhances aerobic metabolism and increases protein synthesis.
Testosterone decreases with age in both men and women.
Testosterone replacement has been used to treat some postmenopausal symptoms, especially lack of libido in women who have received chemotherapy. Recent research on the effects of testosterone on aging demonstrates a gain in lean body mass and a possible decline in bone loss when used in elderly patients. There is significant diurnal variation in testosterone levels in both men and women. It is important to note the time of day clinical samples are collected. Salivary testosterone represents the unbound serum fraction, therefore levels are lower than serum levels.