GH-axis peptides: grading the evidence

Several peptides are sold under the label "GH-axis support": they prompt the pituitary to release growth hormone, raising IGF-1, the downstream mediator of most GH anabolic effects. The category covers GHRH analogues such as tesamorelin and CJC-1295, and GH secretagogues such as ipamorelin. They are grouped together in vendor copy as though the evidence were uniform. It is not. A 2026 review in the American Journal of Sports Medicine noted that clinicians and patients need to understand the "current lack of evidence to support the clinical use of these peptides" for the indications most often discussed^[7].

Tesamorelin: FDA-approved, indication-specific

Tesamorelin (Egrifta) is the only GH-axis peptide with Phase 3 RCT data and a regulatory approval. The FDA approved it in 2010 for reduction of excess abdominal fat in HIV-infected adults on antiretroviral therapy. The approval rests on two randomised, double-blind, placebo-controlled trials. A pooled analysis (N=806, 2:1 to tesamorelin 2 mg or placebo, 26 weeks plus a 26-week extension) found that visceral adipose tissue fell by a mean 24 cm² in the tesamorelin arm versus a 2 cm² rise on placebo (P less than 0.001), and IGF-1 rose 108 ng/ml versus 7 ng/ml^[3]. A separate trial (N=404) confirmed the VAT reduction and showed no significant change in glucose parameters^[4].

These datasets are the strongest in the class, and they are specific to HIV lipodystrophy. The trials were not designed to evaluate tesamorelin in healthy adults or for athletic body-composition goals. Off-label use in those populations has no RCT support. The EMA application was withdrawn in 2012; tesamorelin has no approved indication in the EU, EEA, or UK.

CJC-1295: target engagement shown, no efficacy trial completed

CJC-1295 is a modified GHRH analogue with a maleimidopropionyl linker that binds plasma albumin, extending the half-life from roughly two minutes to five to eight days^[1]. Two published human studies from 2006 represent the entirety of the controlled clinical data.

Teichman and colleagues ran a randomised, double-blind, placebo-controlled trial in healthy adults aged 21 to 61 years. A single CJC-1295 injection produced two- to tenfold GH increases for six days or more and raised IGF-1 1.5- to 3-fold for nine to eleven days; multiple doses showed cumulative effects up to 28 days. The compound was "safe and relatively well tolerated" at 30 and 60 mcg/kg^[1]. Ionescu and Frohman found that continuous CJC-1295 stimulation raised mean GH roughly 46% and IGF-1 45%, while the frequency and magnitude of GH pulses remained unaltered, suggesting the analogue amplifies rather than disrupts the normal secretory rhythm^[2].

ConjuChem's development programme stalled after 2006. No Phase 2 or Phase 3 efficacy trial has been completed for any indication. CJC-1295 is not approved anywhere and is WADA-prohibited under S2. Vendors frequently conflate it with MOD-GRF(1-29), the short-acting version without the albumin linker, which has a different half-life and different pharmacological profile.

Ipamorelin: one PK study, one negative Phase 2

Ipamorelin acts on the ghrelin receptor to stimulate GH release. The 1998 preclinical characterisation by Raun and colleagues described it as "the first GHRP-receptor agonist with a selectivity for GH release similar to that displayed by GHRH": it raised GH without meaningfully elevating cortisol or ACTH, even at doses 200-fold above the GH-effective threshold^[5].

The only published human pharmacokinetic study (Gobburu et al., 1999) confirmed that ipamorelin reaches the pituitary and triggers GH secretion in healthy male volunteers: half-life approximately two hours, GH peak at 0.67 hours post-dose. That study characterised the pharmacology; it did not test a clinical endpoint^[6]. The one published Phase 2 trial involving ipamorelin in humans tested it for postoperative ileus after bowel resection (N=114). Ipamorelin did not meet its primary endpoint; the median time to first tolerated meal was 25.3 hours in the ipamorelin group versus 32.6 hours on placebo (p=0.15). No Phase 2 or Phase 3 trial of ipamorelin for any GH-axis indication has been published^[6].

What the evidence hierarchy means in practice

For someone weighing claims about these peptides, the hierarchy is clear. Tesamorelin has Phase 3 RCT data and an FDA approval for a specific indication in a specific population. CJC-1295 has two small early-phase studies showing it raises GH and IGF-1 in healthy volunteers, with no efficacy data beyond that. Ipamorelin has pharmacokinetic characterisation in volunteers and one negative Phase 2 trial in an unrelated indication. Showing that IGF-1 rises in blood is target engagement, not clinical efficacy. A large randomised trial of the oral GH secretagogue MK-677 (N=563) raised IGF-1 by 72.9% at 12 months yet found no significant difference on any Alzheimer's disease outcome measure, illustrating that biological activity does not automatically translate to the outcomes most often claimed. Per-country regulatory status is on the ipamorelin page and the CJC-1295 page.

What we don't know yet

Long-term GH/IGF-1 elevation in people without documented GH deficiency is not well-studied for safety. Pathological GH excess (acromegaly) is associated with joint pain, insulin resistance, and soft-tissue overgrowth. Whether the IGF-1 increases seen in CJC-1295 and ipamorelin studies produce comparable effects over years of use is unknown. There is no published multi-year safety study for either compound in healthy adults. The tesamorelin extension data runs to 52 weeks in an HIV-positive population, not the population most likely to encounter these compounds through grey-market sources.