A preliminary review of clinical trials suggests that GLP-1 medications — the popular drug class used for weight loss and Type 2 diabetes — may do more than help men lose weight. Researchers say the drugs may improve testosterone levels and sperm quality in men with obesity-related low testosterone.

The findings were presented at the Endocrine Society’s annual meeting in Chicago and were highlighted in a Nature news report. The research focused on healthy men ages 18 to 65 and reviewed published randomized controlled trials comparing GLP-1 drugs with placebo or other treatments.

Scientists at University Hospitals Coventry and Warwickshire and Warwick Medical School in the United Kingdom examined changes in testosterone and other hormones involved in testicular function, along with sperm quality, body weight, blood sugar, cholesterol, and overall metabolic health. Two independent reviewers screened the evidence to reduce bias, and five clinical trials met the researchers’ eligibility criteria.

Across those trials, GLP-1 drugs showed no negative impact on reproductive hormones, sexual function, or sperm quality. In one 24-week semaglutide study, men had improvements in sperm morphology — the size and shape of sperm — as well as cholesterol levels, while testosterone and related hormone levels remained stable.

Another 16-week study of liraglutide in men with obesity-related low testosterone found increases in testosterone and related hormones. The men also had better overall health outcomes than those treated with testosterone replacement alone, according to the research team.

That comparison is important because testosterone replacement therapy can raise testosterone levels but may suppress sperm production, a concern for men who are trying to preserve fertility. The new findings suggest that, for some men with obesity-related low testosterone, improving metabolic health may help address the underlying problem rather than simply replacing the hormone.

“This work supports a shift away from prescribing testosterone replacement in men with obesity and low testosterone and toward treating the underlying cause — excess weight and poor metabolic health — which can naturally restore hormone levels and preserve fertility,” said Dr. Pratibha Natesh, an endocrinologist and team leader at Warwick Medical School.

Researchers emphasized that the reproductive benefits observed in the trials are likely indirect, driven by weight loss and improvements in metabolic health rather than a proven fertility-specific effect of GLP-1 drugs. The medications have not been evaluated as treatments for male infertility or hypogonadism.

Natesh also cautioned that the evidence base remains small and that larger, better-designed studies are needed before doctors can draw firm conclusions about GLP-1s and male fertility. Still, the findings may reassure men who are taking or considering GLP-1 medications for obesity or diabetes and are concerned about possible effects on testosterone or sperm quality.

“Improving metabolic health can have positive effects far beyond weight alone,” Natesh said, according to a press release by the Endocrine Society.