Free testosterone: the norm in men and women
The content of the article:
- What Free Testosterone Is Responsible For
- Laboratory research: the rate of free testosterone, indications for analysis and the rules for its conduct
- Increased and decreased values of free testosterone
The rate of free testosterone in men ranges from 13.9 to 104 pmol / l. Maintaining hormone levels within the normal range is an important factor in men's health.
Testosterone is a sex hormone that in men is produced by Leydig cells of the testicles under the control of luteinizing hormone, a small part is produced by the adrenal cortex, and some more in peripheral tissues by converting androstenedione. In women, about half of all testosterone is synthesized by the peripheral conversion of androstenedione, the rest is produced by the adrenal glands and ovaries.
Testosterone in men is produced primarily by the testes and adrenal glands.
Normally, 1-2% of free (direct) testosterone circulates in the blood, the rest of the hormone is in conjunction with albumin and globulins that bind sex hormones. Both fractions, i.e. bound and free, make up the total testosterone of the body. The concentration of the free fraction is higher in men than in women. This difference is due to the inhibitory effect of androgens on the synthesis of steroid-binding globulins.
Approximately 60% of testosterone in the body is associated with sex hormone binding globulins. This fraction is not biologically active, which differs from the free fraction, as well as from testosterone associated with albumin, which have biological activity.
The level of the hormone in the body is subject to daily fluctuations, in addition, it changes with age. The peak concentration is observed between 04:00 and 08:00, and the minimum is between 16:00 and 20:00. In women, in contrast to men, the level of the male hormone practically does not change during the day, but fluctuates throughout the menstrual cycle. After 50 years in men and during menopause in women, the amount of testosterone in the blood decreases, which is a physiological norm.
What Free Testosterone Is Responsible For
During intrauterine development, free testosterone is responsible for the formation of primary sexual characteristics in the fetus. During puberty, the free fraction takes part in the development of the genitals and secondary sexual characteristics in males. In addition, the hormone has a stimulating effect on spermatogenesis, regulates nitrogen and phosphorus metabolism, sexual behavior and mood in men and women.
The free fraction affects the development of bone and muscle tissue, the growth of hair on the head and body, as well as the larynx mucosa and sebaceous glands.
Laboratory research: the rate of free testosterone, indications for analysis and the rules for its conduct
The norm of free testosterone in men over 14 years old is from 13.9 to 104 pmol / l, in women over 17 years old - from 1.4 to 24.6 pmol / l. The reference range and units may differ from laboratory to laboratory.
Laboratory determination of the concentration of the free fraction of testosterone is one of the most effective methods for assessing the biological activity of the hormone.
Determination of the concentration of the free fraction is used to diagnose androgenic status, especially when the concentration of globulins that bind sex hormones changes (age-related changes, obesity, cirrhosis or some other liver diseases, thyroid pathology, as well as in women during pregnancy).
Free testosterone analysis is indicated for the following pathologies:
- delayed sexual development;
- premature sexual development;
- identifying the causes of acne;
- dysfunction of the pituitary gland;
- anomalies in the development of the mammary glands;
- endocrine diseases.
In addition, the study is being carried out in patients with prostate cancer in order to control the treatment with antiandrogens and gonadoliberins, as well as in children of undetermined sex.
In addition, the determination of the free fraction may be required in the following cases:
- differentiation of primary and secondary hypogonadism;
- diagnosis of sexual dysfunctions (including infertility) in men;
- suspicion of Alzheimer's disease;
- suspicion of testosterone-producing testicular neoplasms;
- suspicion of virilizing adrenal tumors;
- determination of the causes of hirsutism and virilization;
- menstrual irregularities (especially amenorrhea);
- polycystic ovary syndrome;
- hypertrophy of the clitoris;
- treatment with antidepressants.
For laboratory research, blood is taken from a vein. Women must first agree with the doctor on the time when to donate blood (on which day of the cycle).
Blood sampling for analysis is carried out in the morning (in the absence of special instructions, blood should be donated for analysis until 11:00). After the last meal, at least 8, and preferably 12 hours should pass. Before the examination, it is allowed to drink water, while you should not consume juices, sugary carbonated drinks, tea and coffee. Two days before blood sampling, it is necessary to stop taking androgens and estrogens, on the eve of excluding fatty foods from the diet. For half an hour before blood sampling, physical and mental stress should be avoided (they can increase the level of the hormone), and also quit smoking.
Falsely increased test results can be obtained when taking anticonvulsants, barbiturates, estrogens, a number of antibacterial drugs, anabolic steroids, oral contraceptives, valproic acid. Falsely lowered indicators - when using antiandrogens, corticosteroids, follicle-stimulating hormone, narcotic drugs, glucose, ethanol, some antibiotics, phenothiazines.
In the course of laboratory research, in some cases, the free testosterone index is calculated, which allows you to clarify the alleged diagnosis and, if necessary, adjust the treatment regimen. This calculation is indicated for patients with type 1 diabetes mellitus, acne, seborrhea, non-fungal dermatitis, dandruff, alopecia and some other diseases. The index is calculated from indicators of the concentration of total testosterone and globulin, which binds sex hormones.
Increased and decreased values of free testosterone
A change in the concentration of free testosterone in the blood (can occur both upward and downward) is observed in traumatic brain injuries with damage to the pituitary gland, chest injuries, endocrine diseases.
In boys with premature puberty, the level of the hormone in the blood is increased by 10–25%. In women, a high level of the free fraction is observed with hirsutism, polycystic ovary syndrome, menstrual irregularities, virilizing adrenal tumors, taking a number of drugs, and also with androgen resistance.
With an increased level of the hormone in women, the proportions of the body change according to the male type, the voice becomes coarse, the genitals decrease in size, and infertility develops.
With increased free testosterone in women, virilization occurs
Deficiency of free testosterone in men is noted in hypogonadism, Prader-Willi syndrome (a rare hereditary pathology associated with the absence of a paternal copy of the 15q11-13 chromosome region), dysfunctions of the hypothalamic-pituitary system associated with the production of luteinizing hormone, myotonic dystrophy, cryptorchidism mumps. In addition, testosterone is lowered in Klinefelter's syndrome, Itsenko-Cushing's syndrome, exposure to toxic substances and ionizing radiation, erectile dysfunction, Alzheimer's disease, cytochrome P450 deficiency, testicular trauma, antidepressant use, and chronic alcoholism. Low levels of the hormone are normally observed only in elderly men.
With a decrease in the free fraction of the hormone in patients, weakness, fatigue, weight gain, skin pathologies (seborrhea, acne), psychoemotional disorders, decreased sexual desire, changes in the female-type figure with an increase in mammary glands are observed. An excessive decrease in the level of the hormone in old age increases the risk of developing osteoporosis, diabetes mellitus, and infertility.
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Anna Aksenova Medical journalist About the author
Education: 2004-2007 "First Kiev Medical College" specialty "Laboratory Diagnostics".
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