Hey there.
GLP‑1 medications like semaglutide and tirzepatide are everywhere right now. They’re the most talked‑about weight‑loss tools in the U.S., and for many people, they’re incredibly effective. But as more patients use them, one pattern keeps showing up in real‑world clinical practice:
GLP‑1s don’t just reduce fat - they also reduce muscle. And that muscle loss has real consequences for metabolism, strength, and long‑term health.
This is one of the biggest reasons I'm such a strong advocate for evaluating (and supporting) testosterone during GLP‑1 therapy. For both women and men. Not because everyone needs testosterone, but because muscle is metabolically priceless, and testosterone is one of the body’s most powerful protectors of lean mass. Have you heard the buzz about 'muscle is our organ of longevity'?. Let's protect it.
1. GLP‑1s reduce appetite — and that means less protein
When people eat less, they almost always eat less protein. Less protein → less muscle repair → more lean‑mass loss.
Testosterone helps counter this by supporting:
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Muscle protein synthesis
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Strength and physical function
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Recovery and performance
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Preservation of lean mass during calorie deficits
This is why patients on GLP‑1s often feel stronger and more stable when testosterone is optimized (just ask my husband).
2. Muscle loss slows metabolism — testosterone helps keep it alive
Losing muscle means losing metabolic “engines.” This is one reason some people plateau or regain weight after stopping GLP‑1s.
Healthy testosterone levels support:
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Resting metabolic rate
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Mitochondrial efficiency
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Fat‑to‑muscle ratio
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Long‑term weight maintenance
GLP‑1s help reduce fat. Testosterone helps protect the muscle that keeps metabolism running.
3. GLP‑1s can cause fatigue and low motivation — testosterone helps restore drive
Fatigue, low libido, and reduced motivation are common on GLP‑1s. These symptoms overlap with low testosterone, making it easy to miss the hormonal component.
Supporting testosterone can help improve:
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Energy and stamina
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Mood and mental clarity
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Motivation to move and exercise
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Overall sense of well‑being
When patients feel better, they stay active - which further protects muscle. Again...just ask my husband.
4. Weight loss reveals underlying hormone deficiencies
As inflammation decreases and appetite normalizes, true hormonal imbalances can become more visible. I see this constantly: GLP‑1s don’t cause low testosterone - they unmask it.
Evaluating hormones during weight‑loss therapy helps patients understand what’s happening instead of feeling blindsided by new symptoms.
The Bottom Line
GLP‑1s are incredibly popular - and incredibly effective. But they come with a real risk: muscle loss.
Testosterone is one of the most powerful tools we have to protect muscle, metabolism, strength, and vitality during weight‑loss therapy.
Used together - thoughtfully, safely, and individually - GLP‑1s and testosterone help patients lose fat while staying strong, energized, and metabolically resilient.
So, if you're on a GLP-1 and wondering if testosterone might be a good option for you, come talk to us. We'd love evaluate and see if you're a candidate.
Friendly note: These insights come from my clinical experience and emerging observational data. They have not yet been confirmed in large randomized controlled trials - but the patterns I see are consistent and worth paying attention to. And I think the research will come.
In support of your strength, your metabolism, and your long‑term health,
Andrea XO
Andrea Koch, CNP, WHNP-BC, IFMCP
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