Sex hormone-binding globulin (SHBG)
Why this test?
To find out the status of male hormones (androgens). It is prescribed for men with testosterone deficiency, for women with its excess. A test for total testosterone may be done along with or before the HGH test.
To determine the causes of infertility, reduced sexual activity and erectile dysfunction in men, especially when the indicators of total testosterone do not agree with the clinical picture.
For the diagnosis of polycystic ovary syndrome and diseases characterized by excessive production of androgens.
To assess the existing balance of hormones - together with tests for free testosterone, albumin, prolactin, estradiol and luteinizing hormone.
To determine the level of free androgens by calculating their index (IVT) - together with a test for total testosterone. This makes it possible to find out the amount of testosterone that is not bound to GHSH: ISA = total testosterone / GHSH.
In what cases is it prescribed?
If total testosterone test results are inconsistent with clinical findings, such as decreased sexual activity in men and hirsutism in women.
HGH is a protein that is synthesized in the liver. It binds to testosterone, dihydrotestosterone (DHT) and estradiol (estrogen) and transports them into the bloodstream. The content of GHSH in the bloodstream depends on a person's age, gender, and the intensity of testosterone or estrogen secretion. In addition, liver disease, hyperthyroidism, hypothyroidism and increased body weight affect the level of GHSH in the blood.
The amount of testosterone available for use by the body's tissues depends on fluctuations in the level of HGH. In a normal state, 40% to 60% of testosterone is bound to GSHG, and most of the remaining is weakly bound to albumin. And only about 2% of free testosterone is directly available to tissues.
Analysis of total testosterone does not detect differences between bound and unbound testosterone - it only determines the amount of the hormone in general. In many cases, it is enough to determine the excess or lack of hormone formation in the body, but if the GSHG indicator deviates from normal, then the detected level of total testosterone is not an accurate reflection of the amount of the hormone available to the tissues of the body.
At present time, the analysis of GHSH is not used very often - in most cases, the analysis of total and free testosterone gives enough information.