Excess body fat, particularly around the abdomen, has long been associated with lower testosterone levels in men. New research suggests that modern weight loss medications may help reverse this effect, not by replacing testosterone, but by allowing the body’s own hormone production to recover.
A study presented at ENDO 2025, the Endocrine Society’s annual meeting, examined men with obesity or Type 2 diabetes who were treated with GLP-1 receptor agonists such as Ozempic and Mounjaro. These medications are commonly prescribed for weight loss and metabolic health.
Researchers at SSM Health St. Louis University Hospital reviewed electronic health records from 110 men and tracked testosterone levels before treatment and for up to 18 months after starting the medication. About half of the participants had low or low-normal testosterone levels at baseline. After sustained weight loss, most of these men reached testosterone levels within the normal range. The average participant was 54 years old.
The testosterone increases were modest compared to what is typically seen with testosterone replacement therapy. However, the rise occurred without external testosterone, suggesting that improved metabolic health may help restore natural hormone production.
According to the study’s lead author, endocrinologist Dr. Shellsea Portillo Canales, the findings likely reflect reduced insulin resistance and fat mass rather than a direct hormonal effect of the medications themselves. In other words, the body appears to function better hormonally once excess weight is reduced.
What this means for men already on TRT
The study highlights an important clinical consideration for men who are already using testosterone therapy. When significant weight loss occurs, testosterone levels may rise independently, potentially leading to higher-than-intended levels if TRT doses are not adjusted.
In some cases, clinicians may reduce or discontinue testosterone therapy if blood levels normalize while a patient is using GLP-1 medications. This reinforces the importance of regular blood testing and medical supervision when combining weight loss treatment with hormone therapy.
Important limitations to keep in mind
This research does not prove that GLP-1 medications directly increase testosterone. It was a retrospective analysis, meaning researchers reviewed existing medical records rather than conducting a randomized controlled trial. Testosterone levels were also not measured after participants stopped the medications.
If weight is regained, testosterone levels may decline again. For many men, low testosterone is not only a weight issue but also relates to age, genetics, testicular function, or pituitary signaling.
Weight loss vs testosterone therapy: not the same thing
Some experts caution against assuming weight loss alone can replace testosterone therapy. Dr. Susan Spratt of Duke University noted that many men are prescribed testosterone despite having levels in the low-normal range, when addressing obesity or diabetes might be more appropriate.
At the same time, testosterone therapy remains a valid and necessary treatment for men with true hypogonadism. Untreated low testosterone can affect energy, muscle mass, mood, bone density, sexual function, and fertility.
Normal testosterone levels in adult men typically range from 300 to 1,000 ng/dL, but symptoms and treatment decisions should always be based on both blood results and clinical presentation.
The bigger picture
The study underscores the close relationship between metabolic health and hormonal balance. Weight loss medications may offer a dual benefit for some men by improving cardiometabolic health while supporting healthier testosterone levels. However, they are not a substitute for proper hormonal evaluation.
For men experiencing symptoms of low testosterone, blood testing and individualized medical guidance remain essential, whether weight loss medication, lifestyle change, testosterone therapy, or a combination is ultimately appropriate.