Sex Hormone Binding Globulin (SHBG) is a liver-made protein that binds testosterone and estradiol, controlling how much is free and biologically active. By gating hormone access to tissues, it affects energy use, body composition and glucose handling, cardiovascular risk factors, libido and fertility, mood and cognition, and bone turnover. Because liver, thyroid, insulin, and sex steroids regulate it, SHBG is an integrative marker of metabolic and hepatic health.Low values usually reflect strong insulin and/or androgen signals that suppress liver production—common with insulin resistance, visceral adiposity, fatty liver, or androgen excess. In women, low SHBG raises free androgens and often presents with acne, hirsutism, hair thinning, or irregular ovulation; this is typical in polycystic ovary syndrome. In men, SHBG can be low while total testosterone looks normal; it nevertheless flags metabolic strain and higher cardiometabolic risk.Being in range suggests balanced binding capacity, so free and total sex hormones stay stable across the day. It implies coordinated liver, thyroid, and insulin pathways with steady reproductive, cognitive, and musculoskeletal function. For most adults, a mid-range SHBG aligns with physiologic balance, though age- and sex-specific targets vary.High values usually reflect stronger estrogen or thyroid signals, lower insulin effect, or advanced liver dysfunction increasing SHBG output. In women, higher SHBG lowers free androgens and may relate to lighter menses or fewer androgenic features; it rises markedly in pregnancy. In men, high SHBG can reduce free testosterone despite normal totals, with fatigue, low libido, reduced muscle mass, or low bone density.Notes: Oral estrogens, some anticonvulsants, and thyroid hormone raise SHBG; androgens, insulin, and growth hormone lower it. SHBG tends to rise with age, especially in men. Reference intervals vary by lab, age, sex, and pregnancy; acute illness and assay method also influence results. Interpreting SHBG with total and free testosterone, estradiol, thyroid markers, and metabolic indices is essential.
