Testosteron

Testosteron

Testosterone is a primary male sex hormone and an anabolic steroid. In male humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristics such as increased muscle and bone mass, and the growth of body hair. In addition, testosterone is involved in health and well-being, and the prevention of osteoporosis. Insufficient levels of testosterone in men may lead to abnormalities including frailty and bone loss.

Testosterone is a steroid from the androstane class containing a keto and hydroxyl groups at the three and seventeen positions respectively. It is biosynthesized in several steps from cholesterol and is converted in the liver to inactive metabolites. It exerts its action through binding to and activation of the androgen receptor.

In humans and most other vertebrates, testosterone is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females. Small amounts are also secreted by the adrenal glands.

Biological function

Sexual arousal

Testosterone is one of the hormones controlling libido in human males. Pubertal testosterone changes are known to coincide with pubertal changes in the structure of male genitalia, and in the features of sexual desire.

Bone and muscle

Testosterone effects can be classified as virilizing and anabolic, although the distinction is somewhat artificial, as many of the effects can be considered both. Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of linear growth and bone maturation.

Brain

The brain is also affected by this sexual differentiation; the enzyme aromatase converts testosterone into estradiol that is responsible for masculinization of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with congenital diseases of androgen formation or androgen receptor function, to be associated with functional androgen receptors.

Health risks

Men who produce more testosterone are more likely to engage in extramarital sex. Testosterone levels do not rely on physical presence of a partner for men engaging in relationships (same-city vs. long-distance), men still have more testosterone when not accompanied by their spouse.

See also

• Androgen
• Anabolic steroid
• Hypogonadism
• Testosterone (medication)