Testosterone is the most important of the male sex hormones. These are also known as androgens

Among other things, testosterone promotes the growth of body hair

In a nutshell:

Testosterone is the main male sex hormone. It is mainly formed in the testicles. Metabolic disorders that involve testosterone and other hormones can affect not only men but also women.

What is testosterone?

Testosterone is by far the most important male sex hormone. It also occurs in small quantities in women. Testosterone is produced in the so-called Leydig cells of the testis. In both sexes, the adrenal glands also produce limited testosterone. The testicles are controlled by the pituitary gland and the hypothalamus in the midbrain. The pituitary gland releases the follicle-stimulating hormone ( FSH ) and the interstitial cell-stimulating hormone (ICSH) into the blood. The latter is primarily responsible for testosterone production, while the former controls the formation of sperm – with the help of testosterone.

Which value is normal?

In adult men, the total testosterone concentration in blood serum is 2.41 to 8.27 µg / l. These values ​​apply to tatakelood between eight and ten in the morning. In the evening, the testosterone level drops by about 20 percent.

In women, the testosterone level between the third and fifth day of the cycle is around 0.14 to 0.76 µg / l. The hormone comes from the adrenal gland in women.

A very small percentage of testosterone circulates freely in the blood. The rest is bound to protein, including the so-called sex hormone-binding globulin (SHBG). Sometimes, in addition to the total testosterone value, the doctor also uses the testosterone / SHBG ratio, which depicts the biologically active, free testosterone, for assessment.

The testosterone / SHBG ratio (also called free androgen index) is 7 to 100 percent in men (age-dependent) and under 6 percent in women.

When does the value increase?

Diseases or certain disorders of the adrenal glands can be characterized by large amounts of testosterone in the blood. The effects are of course different for women and men or for girls and boys. Boys/men and girls/women experience sexual development and function disorders. In the course of this, feminization symptoms also appear in women.

Both sexes can also suffer from stunted growth.

For example, the hereditary adrenogenital syndrome (AGS) causes the production of aldosterone and cortisol in the adrenal glands to be disturbed. Instead, more testosterone is produced. Among other things, girls can see the increased hair growth and a lack of breast development. Menstruation does not take place. In boys, increased, premature development of gender characteristics such as the armpit and pubic hair and beard growth indicates early puberty. The gonads in the testicles are immature. As a result, there are different shapes and forms at AGS.

Malignant tumors of the adrenal cortex, which can affect both sexes, very rarely form testosterone.

Beard growth is also stimulated by testosterone

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Younger women with obesity sometimes develop cystic changes in the ovaries (polycystic ovary syndrome, also called PCO syndrome). There are increased testosterone levels that cause masculinization and other disorders. Young women also usually get the rare, mostly benign ovarian tumors (Sertoli-Leydig cell tumors). These tumors can also lead to increased testosterone levels with the corresponding physical changes.

When is the value too low?

Serum testosterone levels may be lower than usual after prolonged physical work. Stress, serious illnesses, hereditary disorders, old age, anesthesia, alcohol, drugs or certain medications can also lower the testosterone value.

Testicular tumors, loss of function of the anterior lobe of the pituitary gland, and increased levels of prolactin in the blood may also result in decreased testosterone levels.

Testosterone levels are also reduced in Klinefelter syndrome. This is a chromosome disorder in which the boy is usually born with two females and one male sex chromosomes (47 XXY).

A low testosterone level can lead to feminization in men. He then develops female traits. For example, breast tissue increases due to the increased growth of the mammary glands (gynecomastia). Among other things, this is typical of the aforementioned Klinefelter syndrome.

The determination of testosterone can also indicate the effectiveness of hormone therapy in prostate cancer.