Free Testosterone (T free, serum)

Why this test?

To identify the causes of early puberty or delayed sexual development in case of boys.

To identify the causes of men impotence and infertility.

For the diagnosis of testosterone-producing tumors of the gonads.

To identify polycystic ovaries and other causes of women virilization.

To monitor prostate cancer treatment with gonadoliberin analogues and antiandrogens.

To identify the causes of acne.

For the diagnosis of hypothalamic-pituitary disorders, assessment of the function of the body's endocrine system.

To clarify the gender of newborns with ambiguous sexual characteristics.

In what cases is it prescribed?

For men: with delayed development of secondary sexual characteristics or early puberty, with a decrease in sexual desire and sexual functions, impotence, if hypogonadism is suspected, with infertility, during andropause ("male menopause"), with severe acne, with osteoporosis.

For women: with an irregular menstrual cycle or absence of menstruation, with infertility, with hirsutism and/or excessive development of male external features, baldness, with acne.
Newborns with ambiguous sexual characteristics may be prescribed an analysis together with determination of the level of other sex hormones and instrumental methods of diagnosis.

Test information

Testosterone is a steroid hormone from the group of androgens (male sex hormones). In case of men, it is produced by Leydig cells in the testicles and in a small amount in the cortex of the adrenal glands, in women - in the ovaries and adrenal glands. The main functions of testosterone are control over the correct development of the male genital organs, increase in the volume of skeletal muscles, stimulation of spermatogenesis, hair growth on the skin in the face, armpits, and pubis.
The secretion of the hormone changes with age - it increases up to 30 years, and after 50 it begins to decrease. Diurnal fluctuations of testosterone are also noted: the peak is between 4 and 8 in the morning and the minimum between 4 and 8 in the evening.

With excessive production of androgens, virilization (secondary sexual characteristics characteristic of men), hirsutism (excessive hair growth according to the male type), hoarseness of the voice, hypertrophy of the clitoris occurs in women. Since testosterone stimulates the function of the sebaceous glands, its increase is often associated with the development of acne. Reduced synthesis of testosterone in men leads to hypogonadism (underdevelopment of gonads), female pattern hair loss, weak development of skeletal muscles, underdevelopment of external genital organs, infertility, enlargement of mammary glands, obesity. Insufficient production of this androgen in elderly men increases the risk of osteoporosis. Total blood testosterone is divided into 3 types: free testosterone (not bound to protein, 1-4% of the total), testosterone combined with sex hormone-binding globulin (60-70%), and testosterone, bound to albumin (weakly bound testosterone, 25-40%).
Free and weakly bound forms are bioavailable testosterone, that is, the one that has biological activity. bound testosterone, in turn, is not active. The level of free testosterone does not depend on changes in the concentration of sex hormone-binding globulin (SHBG). Therefore, if SHPG is increased (with hyperthyroidism, cirrhosis, taking oral contraceptives and antiepileptic drugs, hyperestrogenic conditions, including pregnancy) or decreased (with hypothyroidism, obesity, androgen excess, nephrotic syndrome), the free testosterone test will be more informative than on general