Knowledge Centre
Hormones & blood testsDraft: awaiting clinical review
Sex hormone-binding globulin (SHBG)
A protein that carries testosterone in the blood and helps determine how much is active.
Overview
Most testosterone in the blood is bound to SHBG and is inactive. When SHBG is low, more testosterone is 'free' and active.
SHBG is often reported with testosterone so that a free androgen index (FAI) can be calculated.
What is well established
- SHBG tends to be lower with insulin resistance, a higher BMI and PCOS.
- The combined oral contraceptive pill raises SHBG, which is why androgen tests are best interpreted off hormonal contraception.
Uncertain or emerging evidence
- Reference ranges and calculated indices vary between laboratories, which limits direct comparison of results.
This guide is general information and does not replace advice about your own circumstances. Clinical review pending.