GLP‑1s do not harm male hormones or fertility after long-term use, according to a study being presented Monday at ENDO 2026, the Endocrine Society's annual meeting in Chicago, Ill. In fact, the research team found GLP-1s may improve testosterone levels and sperm quality in men with obesity‑related low testosterone, while also addressing the underlying effects of obesity.
Scientists at the University Hospitals Coventry and Warwickshire and Warwick Medical School in Coventry, United Kingdom, made the discovery after searching medical databases for published randomized controlled trials. They focused on studies that compared GLP-1s to other treatments or placebo in men aged 18–65. While the researchers mainly looked at changes in testosterone and other hormones that control testicular function, they also examined sperm quality, body weight, blood sugar, cholesterol and overall metabolic health. Two independent reviewers checked the studies to reduce bias, and five clinical trials met the eligibility criteria.
These scientific reports showed that GLP-1s have no negative impact on hormones, sexual function or sperm quality. For example, a 24‑week semaglutide study revealed improvements in sperm shape and cholesterol levels, while keeping testosterone and hormone levels stable. In men with obesity and low testosterone due to excess weight, a 16‑week liraglutide study demonstrated that the men experienced increases in testosterone and related hormones. Their overall health outcomes were better than with testosterone replacement alone.
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."
Pratibha Natesh, M.B.B.S., M.R.C.P., M.Res., endocrinologist and team lead, Warwick Medical School
While the health outcomes of these clinical trials are positive, Natesh stressed that the number of studies is small with varying results, so larger and better designed studies are still needed to fully understand the effects on male fertility. In addition, physicians should keep in mind that most of the reproductive benefits observed are likely indirect and that GLP-1s have not been evaluated as treatments for male infertility or hypogonadism.
Nevertheless, by offering clear, evidence‑based information about GLP‑1 weight‑loss and diabetes medications, Natesh hopes the research will help people make informed decisions about these drugs.
"Improving metabolic health can have positive effects far beyond weight alone," she said.
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