A new potential benefit has emerged for the latest generation of obesity medications: they may help improve male fertility by increasing testosterone levels and enhancing sperm quality, according to a preliminary review presented at the Endocrine Society’s annual meeting in Chicago, Illinois.
The findings, reported by Nature, suggest that glucagon-like peptide 1 (GLP-1) medications, widely used for treating obesity and related conditions, could have effects beyond weight reduction. Researchers found early evidence that these drugs may help men with obesity and low testosterone levels, although they caution that more comprehensive clinical trials are required before firm conclusions can be drawn.
The systematic review was conducted by researchers including Pratibha Natesh, an endocrinologist at Warwick Medical School in Coventry, UK. The team examined existing randomized controlled trials involving GLP-1 medications and testosterone measurements in men. Despite growing interest in the drugs, researchers found only five studies that met their criteria.
Most modern obesity drugs introduced over the past five years work by targeting the same receptor as the naturally occurring hormone GLP-1. By activating this pathway, the medications create a feeling of fullness and help regulate appetite. Scientists have increasingly studied their wider effects on metabolism, and the latest review examined whether these changes could also influence male reproductive health.
One of the studies reviewed involved 30 men with obesity and hypogonadism, a condition characterized by low testosterone levels. Participants were randomly assigned to receive either a GLP-1 medication or testosterone replacement therapy. After 16 weeks, testosterone levels had increased in both groups.
A separate study examined 25 men with type 2 diabetes and hypogonadism. Participants were again assigned either a GLP-1 medication or testosterone replacement therapy and were followed for 24 weeks. Testosterone levels rose in both groups, although the increase was greater among those receiving testosterone therapy.
However, researchers observed a difference in sperm outcomes between the two treatments. Among participants receiving the GLP-1 medication, sperm quality improved, with the proportion of morphologically typical sperm — those with the expected shape and size — increasing from 2% at the beginning of the study to 4% at the end. In the testosterone replacement group, sperm count and quality declined, a result researchers said is expected with this type of therapy.
The remaining three studies included in the review involved healthy men who used GLP-1 medications for short periods. Those studies found no measurable impact on testosterone levels, highlighting the need for further investigation into which groups of patients may experience reproductive benefits.
Additional research has also pointed toward a possible connection between obesity medications and increased testosterone. At the American Urological Association annual meeting in Washington DC, Andrés Guillén-Lozoya, a physician at the Mayo Clinic in Rochester, Minnesota, presented findings based on electronic health records from more than 1,600 men who had been prescribed obesity medications.
The analysis found that testosterone levels increased by about 30% after treatment with either a GLP-1 medication or a medication that targets both GLP-1 and another hormone pathway involving glucose-dependent insulinotropic polypeptide.
A separate retrospective study examining 215 men receiving weight-loss medications found that testosterone levels after treatment were, on average, around 20% higher than before treatment.
Researchers say the possible link between obesity medications and fertility is consistent with existing knowledge about how excess weight affects male reproductive health. Obesity is known to reduce testosterone levels, a hormone essential for sperm production. One factor behind this relationship is the activity of fat cells, which contain high levels of an enzyme that converts testosterone into oestradiol, the main female sex hormone.
Beyond hormonal changes, obesity is also associated with metabolic disruptions and increased inflammation, both of which can interfere with testosterone production and reproductive function.
The findings may have implications for doctors treating men who have obesity, low testosterone symptoms, and plans to conceive. Symptoms associated with low testosterone can include reduced libido, depressed mood and muscle loss.
Natesh said the emerging evidence suggests that addressing obesity through lifestyle changes and, where appropriate, weight-loss medications could be a strategy for some men experiencing low testosterone. She emphasized that treatment decisions should consider the broader health picture rather than immediately moving to testosterone replacement therapy.
The review’s authors stress that the current evidence remains limited and that stronger research is needed to determine the long-term effects of GLP-1 medications on male fertility. As the use of obesity drugs continues to expand, researchers are now examining whether their benefits extend beyond weight management to other areas of health, including reproductive outcomes.
