Tesamorelin, MK-677, and IGF-1 LR3: muscle-building miracle or overhyped risk?

What did @nickantico actually say?

Short and direct: "My top three peptides for putting on muscle mass is Tess Morellen, MK-677 and IGF-1 LR3." That's the whole claim. No dosing, no mechanism, no context about who these are appropriate for. Just a confident ranked list dropped in front of over 600,000 viewers. These three compounds sit in very different regulatory and scientific categories, and collapsing them into one tidy muscle-building list papers over some meaningful distinctions that matter for anyone actually considering these.

Does the science back this up?

Partially, and the degree varies wildly by compound. Tesamorelin has the strongest human evidence, though not for the reason the creator implies. It is FDA-approved for HIV-associated lipodystrophy, and studies such as Falutz et al. (2010, New England Journal of Medicine) show it reduces visceral fat and modestly improves lean mass in that population. Extrapolating that to general muscle building in healthy adults is a stretch. MK-677, a ghrelin mimetic and growth hormone secretagogue, has shown some lean mass preservation in older adults in short-term trials (Nass et al., 2008, Annals of Internal Medicine), but the effect sizes are modest and side effects like insulin resistance and edema are real concerns. IGF-1 LR3 has almost no peer-reviewed human data. Most citations come from in vitro or animal studies, which is a significant problem when you're recommending something to a mass audience.

What did they get wrong or right?

Credit where it's due: these three compounds do interact with GH and IGF-1 pathways that are genuinely relevant to muscle protein synthesis. That part is biologically coherent. But the creator got the framing wrong in a few important ways. First, tesamorelin's approved use is disease-specific, not performance-based. Presenting it as a general muscle-building tool misrepresents its clinical purpose. Second, MK-677 is not a peptide. It is a small-molecule oral secretagogue. Calling it a peptide is technically inaccurate, even if it acts on similar pathways. Third, and most concerning, IGF-1 LR3 is a modified analog with no approved human use and a theoretical cancer risk that researchers have flagged due to IGF-1's role in cell proliferation (Pollak, 2008, Nature Reviews Cancer). Presenting it casually alongside an FDA-approved drug without that context is irresponsible.

What should you actually know?

If you're a healthy adult looking to build muscle, none of these compounds have robust evidence in that specific context. Resistance training and adequate protein intake have far more human data behind them than any of the three compounds on this list. These are not supplements you pick up and try based on a TikTok. Tesamorelin requires a prescription. MK-677 exists in a regulatory gray zone and is not approved by the FDA for any indication. IGF-1 LR3 is classified as a research chemical and is not approved for human use in the United States. Anyone pursuing these should be doing so under physician supervision with full bloodwork, not because a fitness creator listed them as their top three. The GH and IGF-1 axis is not something to tinker with casually. Chronic elevation of IGF-1 has been associated with increased cancer risk in epidemiological literature, which is a conversation this video never comes close to having.

Bottom line: is the claim accurate?

Mostly misleading by omission. Each compound on the list has some biological rationale for affecting body composition, but none of them have strong clinical trial evidence for muscle building in healthy adults, one is not a peptide, one is a research chemical with real safety unknowns, and the FDA-approved one is approved for a specific disease state. A list this influential, with this little context, does viewers a disservice.