Testosterone is a steroid hormone which is secreted by Leydig cells situated in the testes of male. It is responsible for the proper development of male sexual characteristics. It also maintains muscle bulk, adequate levels of red blood cells, bone density, sense of well-being, libido, and sexual and reproductive function. Small amounts are also produced by the adrenal glands.
In men, testosterone plays a key role in the development of male reproductive tissues such as the testis and prostate as well as promoting secondary sexual characteristics such as increased muscle and bone mass and hair growth. In addition, testosterone is essential for health and well-being as well as preventing osteoporosis.
On average, an adult human male body produces about ten times more testosterone than an adult human female body, but females are, from a behavioral perspective rather than from an anatomical or biological perspective, more sensitive to the hormone. However, the overall ranges for male and female are very wide, such that the ranges actually overlap at the low end and high end respectively.