Popular weight loss medications like Ozempic can help reverse low testosterone levels in men with obesity or Type 2 diabetes, according to new research.
Building on previous studies that show weight loss surgery or lifestyle changes can increase testosterone levels in the body, researchers at SSM Health St. Louis University Hospital analyzed the electronic health records of 110 men with obesity or Type 2 diabetes to monitor changes in the hormone while taking GLP-1 receptor agonists, such as semgalutide and tirzepatide.
They measured testosterone levels before taking the medications and for 18 months after starting the treatment. Roughly half of the men had low to low-normal testosterone at the start of the study and most reached normal levels after treatment. The mean age of the participants was 54.
“The increases we observed were more modest than what you would typically see with testosterone replacement therapy,” said lead author Dr. Shellsea Portillo Canales, endocrinologist at SSM Health St. Louis University Hospital, via email. “However, they occurred naturally, without testosterone replacement therapy (TRT), and likely reflect the body recovering its normal hormone production as weight and insulin resistance improved.”
The study highlights the need for men already on testosterone therapies to closely monitor their levels after starting weight loss medications, Portillo said.
In some cases, men may need to have their testosterone supplement doses lowered or discontinued, especially if their testosterone normalizes while on weight loss medications.
There are limitations to the new study. The findings don’t prove the increase in testosterone levels was caused by the drugs semaglutide or tirzepatide. It was a retrospective study, meaning the researchers analyzed existing medical records over time, rather than conducting a randomized clinical trial. And they didn’t check testosterone levels after the men stopped the drugs.
“If weight is regained, testosterone levels could potentially drop again,” Portillo said.
The study findings were presented this Monday at ENDO 2025, the Endocrine Society’s annual meeting in San Francisco. The researchers are planning to submit it to a medical journal for peer review.
Dr. Susan Spratt, professor of medicine at Duke University School of Medicine, said many men are overtreated with testosterone therapy when they have levels on the lower normal side. “It would be better to treat obesity or diabetes and naturally increase testosterone than to prescribe testosterone — which has known risks,” said Spratt, who was not part of the study.
Some risks of testosterone therapy include worsening sleep apnea, acne, enlarging the prostate or breasts, increasing growth of prostate cancer, reducing sperm counts, causing the testicles to shrink and increasing the risk of clots, according to Mayo Clinic.
The study shows the dual benefit of weight loss medications in men, said Dr. Fatima Cody Stanford, obesity medicine physician scientist at Massachusetts General Hospital and Harvard Medical School.
“The findings from this study highlight an important intersection between metabolic health and hormonal balance,” Stanford said. “This dual benefit underscores the potential of these medications to enhance overall health outcomes, including reproductive health, in this population.”
Normal testosterone levels are between 300 to 1,000 nanograms per deciliter.
Testosterone tends to decline gradually with age, starting around the late 30s to early 40s. By age 75, the average male testosterone level drops to about 65% of the average level seen in young adults, Portillo said.
“Improving testosterone can enhance quality of life and possibly reduce health risks associated with low levels,” Portillo said.
Spratt said it’s important to distinguish between normal testosterone levels that increase but remain in the normal range, versus low testosterone levels that increase to normal.
Testosterone levels that are truly low are most concerning because low testosterone can lower bone density (which increases the risk of fracture), reduce muscle mass, lower hemoglobin (red blood cells) levels and decrease libido, experts say.
“However, treating low normal testosterone without a known cause is controversial and has increased in the past decade likely due to direct-to-consumer marketing,” Spratt said.
The researchers only included men in the study, because they didn’t expect weight loss drugs to raise testosterone levels in women.
“In general, we don’t routinely measure testosterone in women, unless there are signs of a hormonal imbalance, like excess facial hair (hirsutism), irregular periods, infertility or signs of masculinization,” Portillo said.
In those cases, testosterone testing can help diagnose conditions like polycystic ovary syndrome, or PCOS, adrenal disorders or rare tumors.
Some studies in women with PCOS, a condition which raises testosterone levels, suggest GLP-1 therapies may help slightly lower testosterone by improving metabolism and reducing insulin resistance.
Certain conditions are well known to decrease testosterone in men, including excess fat, especially around the abdomen, which interferes with hormone signals from the brain to the testicle, experts say.
“Fortunately, weight loss, whether through lifestyle changes or medications, can reverse it in many cases,” Portillo said.
NBC News
