GLP-1 VS TRT: SEMAGLUTIDE IMPROVES SPERM WHILE TESTOSTERONE THERAPY DESTROYS IT

THE LJUBLJANA STUDY

Published in November 2024, researchers at the University Medical Centre Ljubljana randomized 25 men with type 2 diabetes and functional hypogonadism (low testosterone caused by metabolic factors, not testicular failure) to receive either semaglutide or injectable testosterone for treatment.

Both groups had the same goal: address symptoms of low testosterone including fatigue, low libido, and erectile dysfunction. But the effects on fertility couldn't have been more different.

THE HEAD-TO-HEAD RESULTS

Both treatments improved testosterone levels and both improved symptoms of low T. The critical difference was what happened to the reproductive system.

WHY TRT SUPPRESSES FERTILITY

This isn't a surprise finding — urologists have known for decades that exogenous testosterone suppresses sperm production. Here's why:

Your brain constantly monitors testosterone levels. When it senses enough testosterone (whether produced by your testes or from a medication), it reduces production of two key hormones: LH (luteinizing hormone) and FSH (follicle-stimulating hormone). These hormones tell your testes to produce both testosterone AND sperm.

When you take TRT, your brain says "plenty of testosterone here, no need to make more" and dramatically reduces LH and FSH. Your testes essentially go into hibernation mode. Testosterone levels stay high (from the medication), but sperm production craters — often to near-zero.

WHY GLP-1S PRESERVE (AND MAY IMPROVE) FERTILITY

GLP-1 medications work through a completely different mechanism. Instead of adding external testosterone, they help your body produce its own by reducing the metabolic dysfunction that caused low T in the first place.

The Ljubljana study found that semaglutide actually increased LH and FSH — the opposite of TRT. This suggests GLP-1s restore normal HPT axis function rather than suppressing it.

Additionally, GLP-1 receptors have been found in testicular tissue, including Sertoli cells (which nurture developing sperm) and Leydig cells (which produce testosterone). Early research suggests GLP-1 signaling may directly support testicular function, though this mechanism is still being studied.

WHO SHOULD CARE ABOUT THIS

Choose GLP-1s Over TRT If:

• You're planning to have children in the next 5+ years
• You might want kids someday (even if not planning now)
• Your low T is likely caused by obesity/metabolic factors
• You want to address root cause, not just symptoms

TRT May Still Be Appropriate If:

• You've definitively completed your family
• Your low T is from primary hypogonadism (testicular damage/genetic)
• You're not a candidate for GLP-1 medications
• You've lost significant weight without testosterone improvement

WHAT IF YOU'RE ALREADY ON TRT?

The good news: TRT-induced suppression is usually reversible. Most men recover sperm production within 6-12 months of stopping TRT, though full recovery can take up to 24 months in some cases. Some urologists use HCG (human chorionic gonadotropin) during TRT to maintain testicular function, or as a bridge when transitioning off.

If you're on TRT and want to have children, talk to a reproductive urologist or fertility specialist about your options. This is a common situation and there are established protocols.