SHBG (sex hormone-binding globulin)

SHBG (sex hormone-binding globulin) is a protein that binds and carries sex hormones — including testosterone — through the bloodstream.

Obesity lowers SHBG, which in turn lowers measured total testosterone even when the underlying hormonal axis is working normally. That's a big reason obesity can mimic low testosterone on a blood test, and why weight loss often raises the number. See the guide on HRT for men and GLP-1 medications.

Related terms

Hypogonadism — A condition of low sex-hormone production. In men it means low testosterone with symptoms; importantly, the low testosterone that often accompanies obesity is frequently a reversible state ('pseudo-hypogonadism') rather than true, pathologic hypogonadism.

Testosterone replacement therapy (TRT) — Replacing testosterone in men who have hypogonadism (clinically low testosterone plus symptoms), delivered as a gel, injection, patch, or pellet. It is for a specific diagnosis, not a default treatment for the reversible low testosterone that often accompanies obesity.

Menopausal hormone therapy (MHT) — Estrogen, usually combined with a progestogen (when the uterus is present), used to relieve menopausal symptoms such as hot flashes and to protect bone. Often just called 'HRT.' It is associated with less visceral fat but is not a weight-loss treatment.

Hormone replacement therapy (HRT) — Treatment that replaces a hormone the body no longer produces in adequate amounts — most commonly estrogen (usually with a progestogen) for menopausal women, or testosterone for men with hypogonadism. It is not a weight-loss treatment and is separate from GLP-1 medications.

Related guides

How GLP-1 medications affect men vs. women: what the sex differences actually are — The same GLP-1 medication doesn't act quite the same in men and women. On average women lose more weight, get more side effects, and even absorb more of the drug at the same body weight — differences driven partly by estrogen and testosterone. Here's what the research shows about sex differences in weight loss, tolerability, blood sugar, and biology, and what it means for what you should expect.

Men's health on a GLP-1: testosterone, fertility, muscle, and the things worth watching — For men, losing weight on a GLP-1 does more than shrink the scale — it can raise testosterone that obesity was quietly suppressing, and unlike testosterone therapy it tends to preserve fertility. Here are the key men's-health angles the research is starting to fill in: the testosterone connection, sexual function and sperm, protecting muscle and bone, cardiovascular benefit, and sleep apnea — plus why the checkup men tend to skip matters more now.