A blood protein that binds sex hormones such as testosterone, and is often low in PCOS.

Why it matters for PCOS

SHBG is made by the liver and binds sex hormones in the blood, so it sets how much testosterone stays free and active. In PCOS, insulin resistance tends to lower SHBG, leaving more free testosterone circulating. That can contribute to androgen symptoms such as acne, hirsutism, and scalp hair thinning.

SHBG is usually measured by a blood test and read together with total testosterone and the free androgen index, not on its own. A low result is interpreted in the context of your symptoms and cycle pattern, so ask a doctor what your result means.

This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.