Testosterone is an important sex hormone belonging to the class of male hormones called androgens. But this does not mean that men have a monopoly on it, it is also present in women, although it differs in concentration and functions.
Testosterone is produced in the testes and female ovaries, adrenal cortex and adipose tissue. In men, it is secreted largely under the influence of luteinizing hormone by the Leydig cells of the testicles.
These hormones are involved in the growth and repair of reproductive tissues, affect other body tissues and muscle mass.
The norm of testosterone in women is 0.45 - 3.75 nanomoles per liter, in men - 5.76 - 28.14 nanomoles per liter.
Male testosterone levels increase during puberty and decrease after about 40 years. In women during menopause, almost 50 percent less testosterone is produced than at a young age.
Testosterone can be "bound" and "free." Free testosterone, also known as circulating testosterone, has functions combined with physiological and psychological health.
Testosterone has a direct effect on the testes. It is bound to proteins through the bloodstream and is transported to the seminiferous tubules, which have the appropriate receptors (for the hormone). Transport protein (plasma protein) is called the sex hormone binding globulin.
In the body, part of testosterone is metabolized by the enzyme 5-alpha reductase to even more active dihydrotestosterone.
In men in the puberty, testosterone causes the development of the penis, scrotum, side gonads, and secondary sexual characteristics; in adulthood, he takes care of the maintenance of all these male signs.
Although it is not the only "fuel" that promotes sexual desire in men, however, low testosterone levels can affect normal sexual function.
Analysis for free testosterone is of great importance not only for the detection of many diseases, but also for understanding the role that it plays for health in general. With age, its level decreases, presumably it can be associated with physical activity. According to studies, in men with chronic heart failure and low levels of free testosterone, exercise intolerance was observed.
Free testosterone has neurological functions that counteract the effects of degenerative diseases like Alzheimer's, functions related to physical mobility. Presumably, the level of free testosterone decreases when exercise is limited. It also affects reproductive functions, specifically healthy sperm. Studies have shown that increasing free testosterone levels affects sperm concentration and motility.
A causal relationship in a behavioral aggressive reaction in men can also be established. The level of free testosterone during the embryonic stage of human development, during and even after puberty, has an organizational effect on the brain, which includes an increased willingness to aggressive behavior, its strength and intensity.
The free testosterone index is an indicator that determines the ratio of the concentration of “bound” testosterone, respectively, to the concentration of free testosterone, expressed as a percentage. The ratio is usually used to determine the androgenic status of unhealthy people.
Most blood testosterone does not exist as free molecules. Half are closely related to globulin, the other half to albumin. Since only free testosterone is able to bind to tissue receptors, it is believed that it is the best indicator of a person’s androgenic status.