Preliminary study finds testosterone levels increase or stabilize in people taking GLP-1 drugs
Sperm quality improved in obese men after treatment with GLP-1 drugs.
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THE latest generation of obesity drugs could have another potential benefit: improving fertility in men. A systematic review presented today at the Endocrine Society annual meeting in Chicago, Illinois, suggests that GLP-1 drugs may increase testosterone levels and help improve sperm quality in obese men.
The evidence is still preliminary and more robust trials are needed to confirm the association, says review co-author Pratibha Natesh, an endocrinologist at Warwick Medical School in Coventry, UK. But emerging evidence from other sources points in the same direction.
Perfect sperm
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Most of next generation obesity drugs which have come onto the market in the last five years, work by binding to the same receptor as a natural hormone called glucagon-like peptide 1 (GLP-1), create a feeling of fullness. To learn how the drugs affect male fertility, Natesh and his colleagues searched the literature for randomized controlled trials of GLP-1 drugs that included measurements of testosterone levels in men. They only found five studies.
(This article uses the term “men” to reflect language used in the review and other studies, while recognizing that not all people who have sperm identify as men.)
In one study, for example, 30 men with low levels of testosterone, a condition known as hypogonadism, and obesity were assigned to randomly receive either a GLP-1 drug or testosterone replacement therapy (TRT). After 16 weeks, both groups’ testosterone levels had increased.
Another study randomized 25 men with type 2 diabetes and hypogonadism to receive either a GLP-1 drug or TRT. After 24 weeks, testosterone levels increased in both groups, although the increase was greater among those receiving TRT. In the GLP-1 group, however, sperm quality improved. The percentage of morphologically typical sperm – those with perfect shape and size – increased from 2% at the start of the study to 4% at the end. In the TRT group, sperm count and quality decreased, which is expected during this type of therapy.
The other three studies included in the review involved healthy men receiving GLP-1 drugs for short periods and showed that the drugs had no effect on testosterone levels.
Testosterone Boost
The systematic review’s findings are supported by other studies, including research presented last month at the American Urological Association annual meeting in Washington, D.C. by Andrés Guillén-Lozoya, a physician at the Mayo Clinic in Rochester, Minnesota. Guillén-Lozoya and colleagues analyzed the electronic health records of more than 1,600 men who were prescribed anti-obesity medications and found that participants’ testosterone levels increased by about 30% after treatment with a GLP-1 drug or a drug that mimics both GLP-1 and a separate hormone called glucose-dependent insulinotropic polypeptide.
And a retrospective study examined the electronic health records of 215 men treated with weight-loss drugs. It was found that after treatment, their testosterone levels were on average about 20% higher than before treatment.
Effect of fat cells
Scientists say it is not surprising that these drugs can affect male fertility. It is well known that obesity decreases levels of testosterone, a hormone essential for sperm production and therefore fertility. One reason for the relationship between obesity and low testosterone levels is that fat cells contain high levels of an enzyme that converts testosterone into estradiol, the primary female sex hormone. But other metabolic changes and increased levels of inflammation caused by obesity also affect testosterone production.
Natesh says the team’s findings should be an “eye-opener to all endocrinologists” who treat men, especially people who are planning to conceive, and who have both obesity and symptoms of low testosterone, which can include low libido, depressed mood and muscle loss. Data suggests that for people with low testosterone, combating obesity through lifestyle changes and possibly taking weight-loss medications is a reasonable strategy. In many cases, these interventions will be enough to restore testosterone levels.
“I meet a number of patients in this similar situation,” says Natesh. His advice to colleagues who treat people with obesity and low testosterone is not to prescribe “testosterone right away, look at the big picture.”
This article is reproduced with permission and has been published for the first time June 15, 2026.
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