Sex hormone-binding globulin (SHBG) measurement is used in the diagnosis and monitoring of women with androgen overproduction symptoms and signs (e.g. polycystic ovary syndrome and idiopathic hirsutism), in the monitoring of anti-androgen therapy, in the diagnosis of puberty disorders, in the diagnosis and monitoring of anorexia nervosa, as a complementary test in the diagnosis of thyrotoxicosis as well as in the diagnosis and monitoring of insulin resistance and the assessment of the risk of developing cardiovascular diseases and type 2 diabetes, especially in women.
Sex hormone-binding globulin (SHBG), is a 90-100 kDa homodimeric molecular weight glycoprotein synthesized in the liver. SHBG binds steroidal sex hormones with a very high affinity. The order of affinity of steroid hormones to SHBG is dihydrotestosterone (DHT) / testosterone / estrone / estradiol. Although each monomeric subunit contains 1 steroid hormone binding site, the dimer tends to bind to only one hormone molecule (and not to 2). The main function of SHBG is to transport sex hormones into the bloodstream and to the extravascular target tissues. SHBG also plays a key role in regulating bioavailable concentrations of sex hormones through the competition of hormones for available binding sites as well as through fluctuations in SHBG concentration. Due to SHBG's higher affinity for DHT and testosterone compared to estrogens, SHBG also has a significant effect on the balance between bioavailable androgens and estrogens. Elevated levels of SHBG may be associated with symptoms and signs of hypogonadism in men, while decreased levels may lead to female masculinization.
Men have lower levels of SHBG than women, and dietary status is inversely correlated with SHBG levels, possibly mediated by insulin resistance. Even insulin resistance without obesity results in lower SHBG levels. This may be related to increased intraventricular fat deposition and increased cardiovascular risk.
Endogenous or exogenously administered thyroid hormones and estrogens increase SHBG levels. In men, there is also a gradual age-related rise, possibly secondary to the response to a mild decline in testosterone production.
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
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