Research presented at ENDO 2026, the Endocrine Society's annual meeting in Chicago, suggests GLP-1 weight-loss medications may improve testosterone levels, sperm quality, and metabolic health in obese men with hormone deficiencies. A systematic review of five randomized controlled trials — covering men aged 18 to 65 — found the drugs do not suppress male reproductive hormones and, in at least one comparison, outperformed hormone replacement therapy on key health outcomes. The evidence base remains limited, and the authors are calling for larger trials before clinical conclusions can be drawn.
The Obesity-Fertility Link Driving the Research
Excess body weight disrupts the hypothalamic-pituitary-gonadal (HPG) axis, the hormone system that governs testosterone production, and can trigger functional hypogonadism — abnormally low testosterone caused by disrupted signaling rather than structural disease. The review measured testosterone, brain hormones involved in sperm production, a sex-hormone-binding protein, semen quality, weight, BMI, cholesterol, and blood sugar across all five trials.
Drug-by-Drug Trial Results
| Drug | Trial Length | Key Finding |
|---|---|---|
| Dulaglutide | 4 weeks | No significant change in reproductive hormones or sexual function |
| Liraglutide | 16 weeks | Improved hormones in obese men with functional hypogonadism; superior to hormone replacement therapy |
| Liraglutide | Not reported | Improved sperm concentration and count |
| Semaglutide (Ozempic / Wegovy) | 24 weeks | Improved sperm shape and bad cholesterol; total testosterone preserved |
The authors concluded that GLP-1 drugs "do not appear to acutely suppress the male HPG axis and may improve reproductive hormones and semen parameters in obese hypogonadal men, largely within the context of weight loss."
GLP-1s vs. Testosterone Replacement Therapy
Dr. Anthony Puopolo, men's health expert and lead medical provider at RexMD, was not involved in the study but said the findings provide early evidence that GLP-1 medications improve testosterone in obese men with low hormone levels. He argued that GLP-1s may ultimately prove a better option than testosterone replacement therapy for this population: GLP-1 medications preserve fertility, whereas testosterone replacement therapy tends to impair sperm function.
Why the Findings Remain Preliminary
Only five trials entered the systematic review — a pool the authors characterized as limited and heterogeneous. They called for larger randomized controlled trials explicitly powered to assess male reproductive outcomes. No adverse reproductive effects were reported across the reviewed studies, but the small evidence base means the association between GLP-1 use and fertility improvement requires further confirmation before it can shape clinical practice.