SHBG

REF 21-01

ELISA kit ("sandwich" type) for the quantitative determination of sex hormones binding globulin (SHBG) in human serum.

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 molecular weight of 80 to 100 kDa (depending on its glycosilation degree).

Steroid hormones circulate in blood partially free and partially complexed with albumin and corresponding specific protein (SHBG at sex steroids). The sex steroid hormone fraction not bound to SHBG (so-called bioavailable hormone) can perform regulatory function in target cells. Steroids that bound to albumin are also bioavailable, because in this case the link is too weak to prevent hormone’s diffusion into the target cells.

SHBG shows maximal affinity to androgens and a lesser one to estrogens. SHBG synthesis is affected by sex steroids. Estrogens show a stimulating effect, whereas androgens inhibit the synthesis. In healthy human, SHBG concentration may vary over a vide range. In general, its concentration in women is higher than in men. SHBG concentration increases at hyperthyroidism or hyperestrogenia (lutheal phase of the cycle, pregnancy, intake of estrogen-containing oral contraceptives, cirrhosis etc.). In adult men the concentration of bioavailable testosterone decreases with age due to increased concentration of SHBG. In women SHBG concentration decrease correlates with hyperandrogenic status (polycystic ovary syndrome, congenital dysfunctions of adrenal cortex, hirsutism). Moderate decrease in SHBG concentration is also observed in cases of hypothyroidism, Cushing disease, hyperprolactinemia, acromegalia and after administering androgens or progestins possessing a n androgenic effect. SHBG concentration is used to calculate the free androgen index (a ratio between concentrations of total testosterone and SHBG).