SHBG (Sex Hormone-Binding Globulin)
SHBG (sex hormone-binding globulin) is a protein produced by the liver that binds to sex hormones — primarily testosterone and estrogen — in the blood. When bound to SHBG, these hormones are inactive. Only the "free" (unbound) fraction of hormones can enter cells and exert biological effects.
SHBG levels significantly affect the interpretation of total testosterone and estrogen. A person with high SHBG and "normal" total testosterone may have low free testosterone and experience symptoms of deficiency. Conversely, low SHBG with modest total testosterone may have adequate free testosterone.
SHBG is influenced by several factors: it increases with aging, hyperthyroidism, liver disease, estrogen (including oral contraceptives), and low body weight. It decreases with obesity, insulin resistance, hypothyroidism, and androgen use. SHBG is therefore a useful indirect marker of metabolic and liver health.
What It Measures
SHBG measures the concentration of sex hormone-binding globulin protein in the blood. It reflects hormone binding capacity and indirectly indicates the bioavailability of testosterone and estrogen.
Reference Ranges
| Status | Range (nmol/L) |
|---|---|
| Optimal | 30–50 nmol/L (men), 40–120 nmol/L (women) |
| Normal | 10–80 nmol/L (men), 20–150 nmol/L (women) |
| Borderline | < 10 nmol/L or > 80 nmol/L (men) |
| Out of Range | Context-dependent — interpret with total testosterone |
Interpreting Your Results
When Values Are High
Oral contraceptives, hyperthyroidism, liver disease, aging, eating disorders. Results in lower free testosterone and estradiol.
When Values Are Low
Insulin resistance, PCOS, obesity, hypothyroidism, diabetes. Results in higher free androgens — acne, hirsutism, hair loss.
How GATOR Tracks This
Lab Providers
Related Biomarkers
This content is for informational purposes only and does not constitute medical advice. Reference ranges may vary by laboratory and individual factors. Consult a qualified healthcare provider for interpretation of your results and treatment decisions.
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