What is testosterone?

Testosterone is a hormone  that is produced in men’s testicles. It belongs to the group of androgens, also called steroids or anabolic steroids. It is the most important male hormone , since it influences the maintenance of bones and muscles, in the production of sperm and white blood cells, in the maintenance of sexual desire, in the mood, in the distribution of body hair, in the distribution of fat, in cognitive functions … Testosterone promotes protein synthesis and there are studies that also relate it to insulin sensitivity, glucose metabolism and lipids.

As you get older, testosterone production gets lower and your levels decrease progressively.

Despite popular belief, testosterone is not exclusive to men, since it is also present in the female organism , although in a much lower proportion, since its main effects are related to the male sex. In women it is related to aspects such as humor , sexual appetite and the feeling of well-being .

Physiological effects

Testosterone appears during fetal life , in which the testicles of the fetus are stimulated by the mother’s placenta to produce testosterone, a process that continues approximately until ten weeks after birth. After this period, and throughout childhood, this hormone is barely produced. Between ten and thirteen, at the beginning of puberty , there is a stimulus in the brain that causes testosterone production to increase significantly, and is maintained for most of the rest of life (although in the last years of adult life descend).

Testosterone also influences the brain, leading to key changes. Among them, in the production of dopamine : certain areas of the brain are very dependent on testosterone when producing dopamine, a potent natural antidepressant . It is also related to acetylcholine , a neurotransmitter of memory , making it better, and memory in turn participates in virtually all brain processes. Cognition or thinking ability is directly related to testosterone, especially in young and elderly men, increasing spatial processing. Also, low levels of this androgen are usually linked to thedepression  and anxiety .

There have been multiple studies on the relationship between aggressiveness and testosterone level, but this link remains unclear.


Testosterone that is generated mostly (around 95 percent) in the testicles, thanks to the so-called Leydig cells, although it is also synthesized in other tissues. In women it is synthesized in the teak cells of the ovaries and in the placenta , although in smaller quantities. It is derived from cholesterol , like other steroid hormones. And, like most hormones, it is transferred to the blood, where it travels linked to the sex hormone binding globulin and albumin.

Medical uses of testosterone

It is normal for testosterone levels to decrease with age, but if they are lower than they should, doctors may recommend testosterone therapy. A drug based on artificial testosterone is used, which is usually applied to the skin, through injections or through implants.

Although it affects the increase in the levels of this hormone, it can also pose a series of risks that must be assessed. Among the most common are the increase in the amount of red blood cells (which could lead to stroke or blood clots), acne  and other skin problems, worsening of sleep apnea  if previously suffered, increase in the size of the breasts in both women and men, fluid retention or low HDL cholesterol , the so-called good cholesterol.

In certain cases it can also lead to the growth of the prostate gland , which is why it is essential to have an examination or analysis to detect a possible prostate cancer  before starting treatment. If you have had prostate cancer before, you cannot continue this therapy.

Similarly, it is not advisable that children and pregnant or nursing women come into contact with this medicine, since the risks are higher. And in any case, when you follow testosterone therapy, it is necessary to follow the medication recommendations (they are different depending on the type of testosterone used) and have regular checkups.