Ipamorelin

Ipamorelin is a synthetic five-amino-acid peptide that acts selectively at the ghrelin receptor, asking the pituitary for growth hormone. Among the early secretagogues it stood out for producing genuine GH pulses while leaving cortisol, prolactin and ACTH largely alone — and that selectivity is what sets it apart from the older releasing peptides, GHRP-2 and GHRP-6 among them [1].

It holds no FDA approval for anything. In the US it exists only as a compounded prescription. What it gets prescribed for off-label is body composition, recovery and sleep, very often paired with a GHRH analog, usually CJC-1295 or else sermorelin.

The evidence is overwhelmingly preclinical — animals and cell work — with exactly one published human randomized trial, and that trial measured gut motility rather than anything to do with body composition or aging. Weigh the marketing against that. Evidence grade C.

It copies ghrelin — the hormone behind appetite regulation — at the GHSR-1a receptors sitting on pituitary somatotrophs. That triggers a Gq/11-coupled cascade, raises calcium inside the cell and pushes growth hormone out in a pulse [1]. Its selectivity is the defining feature: at the doses used, it does not meaningfully drive ACTH or cortisol, where GHRP-2 and GHRP-6 reliably do [1].

Pairing it with a GHRH analog works because the two hit different receptors, and activating both produces larger pulses than either manages alone. Half-life in humans runs about two hours [2], which is what supports dosing anywhere from once to three times a day in practice.

The human foundation is pharmacokinetic rather than clinical. A study in healthy volunteers characterized the dose-response relationship and showed GH release that reproduced across dosing intervals [2]. That establishes the peptide does what it claims mechanically in people. It was not built to measure lean mass, fat loss or anything else a patient would care about.

One human randomized trial with a clinical endpoint has been published: a 2014 proof-of-concept study in 35 patients recovering from bowel resection, testing it against postoperative ileus. It significantly shortened time to gastrointestinal recovery against placebo [3]. Note what that is — a gut-motility result in surgical patients, which is a considerable distance from the body-composition claims made for it in wellness settings.

Animal work supplies the mechanism without supplying the outcomes. In adult rats it offset glucocorticoid-driven reductions in bone formation, consistent with GH acting anabolically [4]. A rodent model of the same post-surgical gut problem confirmed prokinetic effects that scaled with dose [5]. Among steroid-treated rats it improved nitrogen balance and lowered urea synthesis, which points toward protein anabolism [6]. A 2024 ferret study found it reduced weight loss caused by cisplatin, suggesting possible use in cachexia [7].

What no controlled human trial has measured, as a primary endpoint, is lean mass gained, fat lost, sleep architecture or bone density. Every claim about those in healthy adults is extrapolation from growth hormone physiology plus clinical anecdote.

Compounding prescribers typically give between 100 and 300 mcg an injection, under the skin, anywhere from once to three times daily. Timing usually clusters around training and before sleep, to land with the natural overnight GH pulse. Combined with CJC-1295 or sermorelin, doses tend toward the lower end of that range [2].

With no approved protocol to anchor to, practice varies widely between prescribers — which is worth knowing before assuming any particular regimen is standard. Some practitioners check IGF-1 at baseline and periodically to confirm something biological is occurring. Oral forms have not been studied at all; every piece of published human pharmacokinetic data used intravenous or subcutaneous dosing.

Compounding pharmacies are the only US source, and they do not operate under the manufacturing standards approved drugs are held to, so potency, sterility and purity vary between them. The clean hormonal profile — little cortisol or prolactin stimulation — is the main reason clinicians reach for this over the older secretagogues [1].

Side effects reported from clinical use and anecdote are mild: reactions at the injection site, temporary fluid retention, headache, flushing. Long-term human safety data are essentially nonexistent — no study has followed anyone on it beyond a few weeks. As with anything that raises GH and IGF-1, caution applies to anyone with current or previous malignancy. It should not be used in pregnancy. All use for body composition or aging in healthy adults is off-label.