What does the Sex Hormone Binding Globulin test measure?

Why is Sex Hormone Binding Globulin measured?

SHBG is essential for calculating free androgen index (FAI = [Total Testosterone × 100] ÷ SHBG) and estimating free testosterone bioavailability. In PCOS, suppressed SHBG from hyperinsulinaemia compounds the effect of elevated androgens by increasing the free androgen fraction. In women on oral oestrogen therapy, SHBG is substantially elevated, reducing free testosterone and potentially contributing to androgen deficiency symptoms despite normal total testosterone. SHBG is therefore a critical interpretive adjunct to total testosterone in all female hormone assessments.

Reference ranges

Standard reference

Female: 17–120 nmol/L # REVIEWER FLAG: SHBG reference ranges are sex-specific and vary with age, menopausal status, and oestrogen exposure — confirm Access Medical Laboratories age-stratified female reference range.

Functional medicine optimal

40–80 nmol/L (functional medicine general optimal; SHBG significantly above or below this range requires contextualisation against oestrogen, androgen, and insulin status). # REVIEWER FLAG: Functional optimal range not standardised — reviewer to confirm.

Units

nmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.