Biomarker

Sex Hormone-Binding Globulin (SHBG)

Last updated Sat May 30 2026 00:00:00 GMT+0000 (Coordinated Universal Time)

Observational— Important to interpret testosterone and estradiol correctly

Why it matters for hormone interpretation

About 60% of testosterone is bound to SHBG (high affinity), ~40% loosely to albumin, and only ~2–3% is free. Total testosterone can be misleading when SHBG is abnormal:

High SHBG → total T looks "normal" but free T may be low (symptoms of hypogonadism).
Low SHBG → total T looks "low" but free T may be adequate.

For accurate evaluation of hypogonadism, calculate free testosterone (Vermeulen equation) using SHBG, total T, and albumin.

What raises SHBG

Aging.
Hyperthyroidism.
Cirrhosis / liver disease.
Oestrogen (oral oestrogens; pregnancy).
Anorexia.
Anticonvulsants.

What lowers SHBG

Insulin resistance / metabolic syndrome (strong inverse association).
Type-2 diabetes.
Obesity.
Hypothyroidism.
Growth hormone excess.
Androgens (TRT lowers SHBG).
Glucocorticoids.

Predictive value

Low SHBG independently predicts incident type-2 diabetes in both sexes; it’s a useful insulin-resistance signal in lipid panels.

References

Hammond, G. L. Plasma steroid-binding proteins: primary gatekeepers of steroid hormone action. J. Endocrinol. 230, R13–R25 (2016).