The growth-hormone axis compounds are the most instructive class in this series, because they span the entire evidence spectrum in one family: an FDA-approved drug with completed phase 3 trials, an unapproved compound with genuine published human data, and a set of research peptides whose records are thinner than their reputations. Treating them as one category — "GH peptides" — is exactly the flattening this series exists to undo.
Tesamorelin: the approved end of the spectrum
Tesamorelin is a growth-hormone-releasing-hormone analogue and an approved drug (Egrifta), indicated for excess abdominal fat in HIV-associated lipodystrophy. Its phase 3 trials (Falutz et al., NEJM, 2007, and subsequent confirmatory studies) reported visceral adipose tissue reductions of roughly 15–18% versus placebo over 26 weeks in that population, with IGF-1 elevation as the expected pharmacological signal.
The precision matters in both directions. The efficacy evidence is real, peer-reviewed, and regulatory-grade — for that indication, in that population, as the manufactured drug. Investigators have studied tesamorelin in other contexts (a small trial in HIV-associated cognitive impairment; NAFLD work reporting reduced liver fat), and those are published findings too — in their own populations, at phase 2 scale.
Ibutamoren (MK-677): human data, unfinished story
Ibutamoren is not a peptide — it is an orally active small-molecule secretagogue — but it anchors the middle of the spectrum. Nass et al. (Annals of Internal Medicine, 2008) ran a two-year randomized trial in 65 healthy older adults: daily MK-677 raised GH and IGF-1 to young-adult levels and increased fat-free mass by about 1.1 kg versus placebo, without significant changes in strength or function. Other trials reported increased appetite and, in one heart-failure population, the sponsor halted development. The investigators' conclusion was measured: sustained biomarker changes, modest body-composition effects, functional benefits unproven.
The research secretagogues: CJC-1295, ipamorelin, and relatives
This is the thin end. CJC-1295 has published human pharmacokinetic work (Teichman et al., Journal of Clinical Endocrinology & Metabolism, 2006) showing sustained GH and IGF-1 elevation over days to weeks after single doses — a real human signal, at biomarker level, in small healthy-volunteer studies. Development toward any approved indication stopped there. Ipamorelin was characterized in animal models and early human safety work in the late 1990s (Raun et al., European Journal of Endocrinology, 1998, describes its receptor selectivity in vitro and in rodents); its clinical program, for postoperative ileus, was discontinued after phase 2 did not meet its endpoint.
So the honest summary of the most popular "GH peptides" on the research market: demonstrated biomarker effects in small human studies, no completed efficacy program, and selectivity claims that trace to preclinical characterization. Elevating IGF-1 is a measurable pharmacological event, not an outcome — the distinction between a surrogate and a clinical endpoint, covered in Reading a Peptide Study, does more work in this class than in any other.
What is established, and what is not
Established: tesamorelin's efficacy for its approved indication; ibutamoren's biomarker and modest body-composition effects in randomized human studies; CJC-1295's human GH/IGF-1 pharmacokinetics at small scale.
Not established: functional or clinical outcomes for any research secretagogue; long-term safety of sustained GH/IGF-1 elevation in healthy people (a question the literature itself raises, given IGF-1's role in growth signalling); and the applicability of any of this evidence to unverified material — trial evidence attaches to the tested compound at verified identity and purity, which is what a certificate of analysis exists to establish.
Nothing above is dosing guidance or a treatment claim. Aside from tesamorelin in its approved indication, no compound discussed here is FDA-approved. Research use only.
Sources include: Falutz et al., NEJM 2007; Nass et al., Ann Intern Med 2008; Teichman et al., JCEM 2006; Raun et al., Eur J Endocrinol 1998.
For research use only · Not for human or veterinary use · No compound discussed here is FDA-approved for any indication