ENDO 2026: The 5 Findings Every Man Needs to Know

Testosterone restoration, fertility protection, erectile function, an exercise warning, and the restart data that changes everything. The definitive ENDO 2026 roundup for men.

June 19, 2026

The Endocrine Society's 2026 annual meeting in Chicago didn't just advance endocrine science — it rewrote the playbook for how men should think about GLP-1 medications. Five studies presented at ENDO 2026 carry direct, immediate implications for any man considering GLP-1 treatment, currently using it, or weighing it against testosterone replacement therapy.

Here are the five findings that matter most, what they mean for you, and what to do about each one.

1. GLP-1s Restore Testosterone — Up to 77% Increase

The headline number from ENDO 2026 that should get every man's attention: men on GLP-1 medications who lost 10% of their body weight experienced a 53% to 77% increase in testosterone levels over 18 months of treatment.

The study, led by Dr. Shellsea Portillo Canales, measured total and free testosterone in men using semaglutide, dulaglutide, or tirzepatide — none of whom were taking testosterone therapy. The mechanism isn't mysterious: excess body fat converts testosterone to estrogen via aromatase activity. Lose the fat, and testosterone production rebounds naturally.

This matters because millions of men with obesity are currently prescribed testosterone replacement therapy (TRT) for low T — without ever addressing the metabolic root cause. TRT works, but it comes with a significant trade-off that brings us to finding number two.

2. GLP-1s Preserve Fertility — TRT Does Not

A systematic review of five randomized controlled trials, led by Dr. Pratibha Natesh from the University of Warwick, delivered the most comprehensive evidence to date: GLP-1 medications do not suppress the hypothalamic-pituitary-gonadal (HPG) axis and may actually improve sperm quality in men with obesity.

The specifics are striking. A 24-week semaglutide trial showed improvements in sperm morphology and cholesterol levels while keeping testosterone and gonadotropin levels stable. A 16-week liraglutide trial demonstrated increases in total testosterone, luteinizing hormone, and follicle-stimulating hormone — the hormones that drive sperm production.

"This work supports a shift away from prescribing testosterone replacement in men with obesity and low testosterone and toward treating the underlying cause — excess weight and poor metabolic health — which can naturally restore hormone levels and preserve fertility." — Dr. Pratibha Natesh, Warwick Medical School

Contrast this with TRT, which suppresses sperm production by up to 60.6% and can sometimes cause permanent infertility. For men aged 25–40 who might want children, this finding is a genuine game-changer: you can raise your testosterone and protect your fertility by treating the obesity first.

3. Tirzepatide May Improve Erectile Function Better Than TRT

Erectile dysfunction affects roughly half of men with obesity, and the standard treatment chain — PDE5 inhibitors (Viagra, Cialis), then TRT if testosterone is low — may be incomplete. New research presented alongside ENDO 2026 and published in JACC: Cardiovascular Interventions adds another option to the front of the line.

A retrospective cohort study using the TriNetX global health network found that tirzepatide was associated with a significantly lower risk of developing erectile dysfunction compared to sitagliptin, injectable semaglutide, and dulaglutide in men with type 2 diabetes. A separate pilot study found tirzepatide improved both erectile function scores and hormonal profiles — outperforming both lifestyle modification and TRT.

The proposed mechanism involves weight loss reducing vascular inflammation, improving endothelial function, and restoring nitric oxide production — the same pathway that PDE5 inhibitors target from the other direction. Lose weight, and the plumbing works better on its own.

4. GLP-1 Users Walk 560 Fewer Steps Per Day — a Real Problem

Not every finding was good news. Using Fitbit wearable data linked to electronic health records from the NIH's All of Us Research Program, researchers at HSHS St. John's Hospital found that adults who started GLP-1 medications walked 560 fewer steps per day and did 5.7 fewer minutes of moderate-to-vigorous physical activity (MVPA) daily — despite losing weight.

The study included 753 adults with obesity, and the decline was steepest among men and those with musculoskeletal pain. Steps dropped from 5,047 to 4,487 per day (P < .001), and MVPA dropped from 27.9 to 22.2 minutes per day (P < .001).

Why this matters: GLP-1 medications reduce both fat mass and lean muscle mass. Research estimates 20–40% of weight lost on GLP-1s comes from lean tissue. Physical activity — especially resistance training — is the primary tool for preserving muscle. When patients reduce both calories (via appetite suppression) and exercise simultaneously, the result is accelerated muscle loss even as the scale improves.

What to Do About It

• Start resistance training from day one. At minimum, two sessions per week targeting major muscle groups.
• Track your steps. Use a wearable and set a daily floor — if your baseline is 5,000 steps, don't let it drop below that.
• Prioritize protein. Most guidelines recommend 1.2–1.6 grams of protein per kilogram of body weight daily while on GLP-1 medications.
• Address pain barriers. If joint or muscle pain is reducing your activity, talk to your provider about physical therapy or pain management before it becomes a habit.

5. Most Men Who Stop GLP-1s Eventually Restart

A large retrospective study from Boston University analyzing 60,222 patients with type 2 diabetes found that about 4 in 10 patients stopped their GLP-1 medication within the first year, and nearly 6 in 10 had stopped by two years. But here's the encouraging part: more than half of those who stopped restarted within one year (53.6%), and nearly two-thirds restarted within two years (65.9%).

The most common reason for stopping was gastrointestinal side effects (37%). Patients taking newer medications like tirzepatide were 41% less likely to discontinue than those on older drugs like liraglutide, and semaglutide users were 28% less likely to stop than liraglutide users.

The practical takeaway: if you've tried a GLP-1 medication and stopped due to nausea or other GI issues, you're not alone — and you're statistically likely to come back. Switching to a different GLP-1 or starting at a lower dose may make the difference. These aren't medications most people abandon permanently; they're medications people cycle through until they find the right fit.

Bonus: Beyond ENDO — Two More Findings That Matter

GLP-1s and Cancer Risk

A study published in Annals of Oncology and presented at ASCO 2026 analyzed over 229,000 patients and found that GLP-1 users had a 41% lower incidence of obesity-related cancers compared to those receiving diet and exercise counseling alone. For lung, breast, colorectal, and liver cancers, GLP-1 users were 38–50% less likely to progress to stage IV disease.

Semaglutide Slows Biological Aging

A randomized, placebo-controlled trial from UC San Diego — published in Nature Communications in May 2026 — found that semaglutide slowed the pace of biological aging by 9% as measured by the DunedinPACE epigenetic clock. Effects were seen across markers linked to inflammation, brain, heart, kidney, liver, and metabolic health.

What This Means for Your Next Move

If you're a man with obesity and low testosterone, ENDO 2026 just made the case that GLP-1 medications should be the first conversation — not TRT. You get weight loss, testosterone restoration, fertility preservation, and potentially better erectile function, all from addressing the root cause. But you must pair it with resistance training and adequate protein to protect your muscle mass.

If you're already on a GLP-1 and noticed you're moving less, that's the signal to course-correct before muscle loss becomes the next problem to solve.

GLP-1 Providers for Men

These telehealth platforms offer GLP-1 prescriptions online with consultations tailored for men. Pricing reflects compounded medication options unless noted.