SHBG
Also called Sex hormone-binding globulin, TeBG
SHBG (sex hormone-binding globulin) is a protein, made mostly in the liver, that binds sex hormones such as testosterone and estrogen in the bloodstream. A hormone bound to SHBG cannot act on your tissues; only the unbound, or free, portion can.
That makes SHBG the reason a total testosterone result does not tell the whole story. Two people with the same total testosterone can have very different amounts available to their tissues if their SHBG differs, so clinicians read the two results together to estimate free testosterone.
Why it matters after 45
SHBG moves with things that become common in midlife. Insulin resistance, type 2 diabetes, carrying extra weight and an underactive thyroid are linked with lower SHBG; liver disease, an overactive thyroid and estrogen-containing medicines, including menopausal hormone therapy, are linked with higher SHBG. A result that looks unremarkable on its own can mean something different once SHBG is known, which is why a panel that measures testosterone without it can mislead in either direction.
Where it comes up
- Low testosteronewhy symptoms and a total testosterone result do not always agree
- Getting the testosterone test righttiming, repeat draws and what is measured alongside
- Comprehensive Lab Panelthe baseline panel that includes the hormone markers
- Hormone test costwhat testing costs, and why a repeat is worth budgeting for
References
- MedlinePlus. SHBG Blood Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/shbg-blood-test/
- MedlinePlus. Testosterone Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/testosterone-levels-test/
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms