What does the Sex Hormone Binding Globulin test measure?

Why is Sex Hormone Binding Globulin measured?

SHBG is rarely informative in isolation and derives almost all of its clinical value as a denominator: it is measured to interpret total testosterone correctly and to calculate free and bioavailable testosterone. Total testosterone becomes misleading whenever SHBG is abnormal — a low SHBG in obesity or insulin resistance depresses total testosterone while free testosterone may be preserved, and a high SHBG in ageing, hyperthyroidism, or oestrogen therapy elevates total testosterone while bioavailable hormone may be inadequate. SHBG is also increasingly described as an independent marker of insulin resistance and metabolic risk, a relationship that is consistent in observational data but not yet established as a guideline-actionable clinical target.

Reference ranges

Standard reference

Adult men: approximately 10–57 nmol/L; adult women: approximately 18–144 nmol/L, varying with age, oestrogen status, and pregnancy

Functional medicine optimal

No standardised functional optimal range exists; mid-reference values are sometimes cited, but SHBG is interpreted relative to total testosterone and metabolic context rather than against an independent target

Units

nmol/L, µg/mL

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