Alkor Bio, Ltd.

Sex hormones binding globulin (SHBG) (also known as sex steroids binding globulin – SSBG) is a serum protein that binds to steroid sex hormones. SHBG is synthesized in the liver. It is a dimeric glycoprotein with a molecular weight of 80 to 100 kDa (depending on the degree of glycosilation). Steroid hormones circulate in blood partly in their free form and partly as a complex with albumin and corresponding specific protein (SHBG in the case of sex steroids). Fraction of sex steroid hormone that is not bound to SHBG (so-called bioavailable hormone) can perform the regulatory function in the target cells. Steroids that bound to albumin are also bioavailable, because in this case the bound is weak and does not block the diffusion of the hormone into target cells. SHBG shows maximal affinity to androgens and less – to estrogens. The synthesis of SHBG is affected by sex steroids. Estrogens show stimulating effect, whereas androgens inhibit the synthesis. In healthy individuals SHBG concentration may vary over a vide range. In general, its concentration in 

women is higher than in men. SHBG concentration increases in the case of hyperthyroidism or hyperestrogenia (lutheal phase of the cycle, pregnancy, intake of estrogencontaining oral contraceptives, cyrrhosis etc.). In adult men the concentration of bioavailable testosterone decreases with age due to increased concentration of SHBG. In women decreased concentration of SHBG correlates with hyperandrogenic status (polycystic ovary syndrome, congenital dysfunctions of adrenal cortex, hirsutism). Moderate decrease in SHBG concentration is also observed in the case of hypothyroidism, Cushing disease, hyperprolactinemia, acromegalia and after the treatment with androgens or progestins that have androgenic effect. SHBG concentration is used for calculation of free androgen index (ratio between concentrations of total testosterone and SHBG). SteroidEIA-SHBG kit is intended for the quantitative determination of sex hormones binding globulin (SHBG) in human serum.