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Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
Sex hormone binding globulin is a protein made by your liver that binds tightly to sex hormones, mainly testosterone and estradiol, and carries them through your bloodstream. Only a small portion of these hormones is unbound and available for your body to use. By binding hormones, SHBG helps regulate how much is free and biologically active.
Doctors order an SHBG test to better understand your hormone balance, especially when total testosterone or estradiol levels do not match your symptoms. The test is performed on a blood sample and is often interpreted together with total hormone levels and sometimes albumin to estimate how much free hormone is available to tissues.
SHBG levels can influence how much active hormone is available, so they affect the interpretation of total testosterone and estradiol. If SHBG is high, less hormone is free; if it is low, more may be free, even when total levels look typical. This matters when evaluating concerns such as low libido, erectile difficulties, irregular periods, acne, excessive hair growth, hot flashes, or possible androgen excess or deficiency.
Clinicians may order SHBG when they suspect conditions that change binding proteins or when deciding whether calculated free hormone should guide treatment. SHBG can change with thyroid status, liver function, body weight and insulin resistance, age, and certain medications such as estrogens or androgens. Understanding SHBG helps reduce misclassification of hormone disorders and supports safer, more targeted care.
Your SHBG result is interpreted with your symptoms and other lab tests. Higher SHBG usually means less unbound testosterone or estradiol, and lower SHBG usually means more unbound hormone. This can explain why someone with a typical total hormone level still has symptoms of too little or too much hormone.
If your result is unexpected, your clinician may review medicines, thyroid and liver health, weight and metabolic factors, and whether you are pregnant or approaching menopause. Follow-up may include repeating testing, measuring total and free testosterone or estradiol, checking albumin, or assessing thyroid and liver panels. Decisions about treatment are based on your overall picture, not a single value.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
SHBG is relatively stable, but hormone levels that are interpreted with it can vary by time of day. Your clinician may prefer morning sampling and consistent timing for repeat tests.
Estrogen therapy and some anticonvulsants can raise SHBG, while androgens, anabolic steroids, and glucocorticoids can lower it. High-dose biotin can interfere with some immunoassays; stop biotin as advised before testing.
Overactive thyroid or liver conditions can raise SHBG, and underactive thyroid or significant liver impairment can lower it. Interpreting results often requires checking thyroid and liver tests.
Obesity and insulin resistance tend to lower SHBG, which can increase free androgens. Weight changes and metabolic health can meaningfully shift results over time.
SHBG differs by sex and changes with aging. Pregnancy and menopause can alter SHBG, affecting how total hormone levels reflect what is biologically active.
Serious illness, inflammation, and kidney disorders can alter SHBG and albumin, which can complicate interpretation. Testing may be deferred until you are clinically stable.
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