Sperm quality improved in men with obesity after a course of GLP-1 drugs.Credit: Steve Gschmeissner/SPL
The latest generation of obesity drugs might have another potential benefit: improving fertility in men. A systematic review presented today at the Endocrine Society’s annual meeting in Chicago, Illinois, suggests that GLP-1 medications might increase testosterone levels and help to improve the quality of sperm in men with obesity.
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
Most of the next-generation obesity drugs that have come on the market in the past five years work by binding to the same receptor as a natural hormone called glucagon-like peptide 1 (GLP-1), creating a feeling of fullness. To learn how the drugs affect male fertility, Natesh and her colleagues searched the literature for randomized controlled trials of GLP-1 drugs that included measurements of testosterone levels in men. They found only five studies.
(This article uses ‘men’ to reflect the language used in the review and other studies, while recognizing that not all people who have sperm identify themselves as men.)
In one study1, for example, 30 men with low testosterone levels, a condition known as hypogonadism, and obesity were assigned to receive either a GLP-1 drug or testosterone replacement therapy (TRT) at random. At the end of 16 weeks, the testosterone levels of both groups had risen.
How to keep weight off after obesity drugs
Another study2 randomly assigned 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 a perfect shape and size — went from 2% at the start of the study to 4% by the end. In the TRT group, sperm count and quality declined, which is expected during this type of therapy.
The other three studies3,4,5 included in the review involved healthy men receiving GLP-1 medications for short periods of time and showed that the drugs had no effect on testosterone levels.
Testosterone boost
The findings of the systematic review are supported by other studies, including research presented last month at the American Urological Association annual meeting in Washington DC by Andrés Guillén-Lozoya, a physician at the Mayo Clinic in Rochester, Minnesota. Guillén-Lozoya and his colleagues analysed the electronic health records of more than 1,600 men who had been prescribed obesity drugs and found that participants’ testosterone levels increased by around 30% after treatment with either a GLP-1 drug or a drug that mimics both GLP-1 and a separate hormone called glucose-dependent insulinotropic polypeptide.
