Testosterone replacement therapy (TRT)

Testosterone replacement therapy (TRT) replaces testosterone in men with hypogonadism — clinically low testosterone accompanied by symptoms — using gels, injections, patches, or pellets.

It is meant for a specific diagnosis. Much of the low testosterone seen with obesity is reversible without TRT, and weight loss (including on a GLP-1) often raises testosterone on its own. 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.

SHBG (sex hormone-binding globulin) — A protein that binds and transports sex hormones (including testosterone) in the blood. Obesity lowers SHBG, which reduces measured total testosterone and is a major reason obesity can look like low testosterone on a lab test.

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

HRT for men (testosterone) and GLP-1 medications: what the connection really is — Low testosterone and excess weight are linked — but the arrow often points from weight to testosterone, not the other way, and that changes when testosterone therapy actually helps. Here's who benefits from TRT, and why losing weight on a GLP-1 can raise testosterone on its own.

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.