// research console — tolerability lens
Ipamorelin raises growth hormone without raising cortisol. That selectivity is the whole story.
One discrete GH pulse. A ~2-hour human half-life. One Phase 2 trial that missed its endpoint. Every number logged to the study that measured it.
Start here
Ipamorelin is a small lab-made peptide — a chain of five amino acids. It tells the pituitary (a gland at the base of the brain) to release a short burst of growth hormone, the body's signal for repair and growth. What makes it stand out: it does this cleanly. Older peptides in its class also pushed up cortisol (a stress hormone) and prolactin. Ipamorelin mostly does not [1]. That is its defining trait.
People in research-use communities pair it with other peptides and report better sleep and faster recovery. But here is the honest part. Ipamorelin was never approved as a medicine, anywhere. The one real human trial — for slow bowel recovery after surgery — failed to beat placebo [3]. Long-term human safety has never been studied. What people report — including the downsides — is laid out on the effects page. This site reads the published record straight. It is not a clinic. Nothing here is sold.
What the record actually shows
Ipamorelin (sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a synthetic pentapeptide — a chain of five amino acids built in a lab. It activates the ghrelin receptor, formally GHS-R1a (the docking site the hunger hormone normally uses), on pituitary cells. The result is a pulse of growth hormone (GH).
The founding 1998 characterization measured the trait that named it. In conscious swine the GH ED50 — the dose producing half the maximum GH response — was 2.3 nmol/kg, against 3.9 nmol/kg for the older peptide GHRP-6. At doses more than 200-fold above that, it still did not raise ACTH or cortisol above the level seen with GHRH [1]. That is the selectivity this whole site is built around.
Human data is thin and mostly old. A 1999 study in eight healthy men per dose level put the terminal half-life — the time for blood levels to fall by half during clearance — at about 2 hours, with a single GH pulse peaking near 40 minutes after dosing [2]. The kinetics were dose-proportional. That study, and one failed trial, are nearly the entire human file.
The one human efficacy trial
There is exactly one published Phase 2 randomized controlled trial. It was negative.
114 adults recovering from bowel-resection surgery received 0.03 mg/kg intravenously twice daily for up to seven days [3]. The goal was faster return of bowel function. Median time to the first tolerated meal was 25.3 hours on ipamorelin versus 32.6 hours on placebo — a difference that did not reach statistical significance (p=0.15) [3]. The primary endpoint was missed.
On safety in that short window, treatment-emergent adverse events hit 87.5% of the ipamorelin arm versus 94.8% of placebo [3]. No ipamorelin-specific safety signal surfaced over those seven days. But seven perioperative days is not a long-term safety database. That gap matters, and the Ipamorelin effects page treats it as the loudest fact on the panel.
What animal studies measured
The preclinical record is where most of the positive data lives. In adult female rats, subcutaneous ipamorelin at 18, 90, and 450 microg/day (split three times daily for 15 days) raised the longitudinal bone-growth rate from 42 microm/day on vehicle to 44, 50, and 52 microm/day — dose-dependent, with no measured change in total IGF-1 or bone-turnover markers [4].
The most recent in-vivo study is a 2024 ferret experiment. Intraperitoneal ipamorelin at 1-3 mg/kg cut chemotherapy-induced body-weight loss by about 24% during the delayed phase, yet produced no anti-emetic effect at all [5]. The weight-protection ran through a peripheral mechanism.
Numbers like these are real and cited. They are also rodent and ferret numbers. The reproducible animal record and the empty human record are both findings — this site keeps them apart. The full study set is on Ipamorelin research.
Status, plainly
Ipamorelin is not FDA-approved. It never has been, for any indication, anywhere. Its only Phase 2 program — for postoperative ileus (slow bowel recovery after surgery) — missed its endpoint and no further clinical development followed [3].
It is banned in sport at all times under the WADA Prohibited List, category S2, as a growth hormone secretagogue, and is detectable in urine by accredited labs. In 2024 the FDA removed ipamorelin acetate from Category 2 of the interim Section 503A bulk-substances list and reviewed it at the October 29, 2024 Pharmacy Compounding Advisory Committee meeting — tightening compounding-pharmacy access.
Most available material is research-grade, of variable purity, from unregulated suppliers. This digest documents that landscape. It does not change it, and it does not sell into it. See Ipamorelin references for every source.