Ipamorelin is a lab-made peptide — a very short chain of amino acids, the building blocks of proteins. Its job is indirect and worth getting right: it doesn't add growth hormone to your body, it asks your own pituitary gland to release a pulse of it. It does that by copying the signal of a natural hormone called ghrelin. What made ipamorelin notable when it was first described is one word: selective.
In plain terms: it flips a switch that makes your body release its own growth hormone — and it flips that switch cleanly, without setting off other alarms.
What it is
Ipamorelin is a pentapeptide — exactly five amino acids (Aib-His-D-2-Nal-D-Phe-Lys-NH2)1. It belongs to a family called growth-hormone secretagogues: molecules that make the body secrete (release) its own growth hormone.
There are two different "levers" that trigger growth-hormone release, and ipamorelin pulls one of them. It acts on the GHS receptor — the same receptor the natural "hunger hormone" ghrelin uses. (The other lever is the GHRH receptor, which analogs like CJC-1295 pull.) Because it engages the ghrelin receptor, ipamorelin is in the same class as the older peptides GHRP-6 and GHRP-2 — but it was engineered to be cleaner than them (full comparison).
The selectivity story
This is ipamorelin's whole reason for existing, so it's worth understanding. The peptides that came before it — starting with GHRP-6, the 1984 compound that founded the class2 — did release growth hormone, but they also nudged other hormones: cortisol and ACTH (stress hormones), and prolactin. That "off-target" activity was seen as messy.
In the founding 1998 study, ipamorelin released growth hormone about as strongly as GHRP-6 but did not raise ACTH or cortisol in the animals tested1. That is what "selective" means here: the growth-hormone signal without the extra hormonal side-chatter.
In plain terms: older peptides in this family rang several bells at once; ipamorelin was built to ring mainly the one you want.
What the studies actually found
Almost all of ipamorelin's direct evidence is preclinical — animals and cells. Here are the anchor studies in order, with the model each used and the molecule it tested:
| Study | Model | Key result | Year |
|---|---|---|---|
| Bowers et al.2 | Rat + pituitary cells (GHRP-6) | Founded the class — the first synthetic peptide to make the pituitary release growth hormone through a switch separate from GHRH | 1984 |
| Raun et al.1 | Rat, pig + cells (ipamorelin) | Released growth hormone as potently as GHRP-6 but, unlike it, did not raise ACTH or cortisol — the "selective" result | 1998 |
| Teichman et al.3 | Human (CJC-1295, the GHRH partner) | Showed the complementary GHRH lever produces days-long IGF-1 rises — the rationale for pairing ipamorelin with CJC-1295 | 2006 |
The pattern is a clean, selective growth-hormone pulse in animals. That is genuinely the design goal — but note the honesty flag: it is a *preclinical* result. There is no completed human trial showing ipamorelin produces a specific clinical outcome.
Why it's paired with CJC-1295
Because ipamorelin (a GHS-receptor agonist) and CJC-1295 (a GHRH-receptor analog) pull two different levers on the same system, research studies them together as complementary — the logic being that stimulating both receptors at once produces a larger, more natural pulse than either alone3. This is why the phrase "CJC-1295 and ipamorelin" is almost always said as one breath (the pairing explained).
Pharmacokinetics
Ipamorelin is short-acting — a reported half-life (how long it takes for half a dose to clear) of roughly 2 hours (curve). That short window is exactly why it's combined with a long-acting partner: ipamorelin provides a brief, clean pulse, while a DAC-modified GHRH analog sustains the background signal for days.
Regulatory status
Ipamorelin is not an approved medicine. In 2023 the FDA placed it (with several other research peptides) on the Category 2 portion of its interim 503A list of bulk substances for compounding pharmacies — a "needs further evaluation for safety/efficacy" bin4. That status has kept moving since — some nominations were withdrawn in 2024 and the advisory committee has scheduled further review — so treat the exact regulatory picture as a snapshot, not a settled rule. This page takes no position on sourcing and never discusses it.
Latest research
- The strongest recent human data in this corner of the field is not about ipamorelin itself but its GHRH partner — the CJC-1295 pharmacokinetic work that underpins the pairing rationale3.
- Regulatory review of the peptide is ongoing through the FDA's compounding advisory process, so the compounding status is the most likely thing to change next4.
- We update this section as new studies land.
The short version
Ipamorelin is a small, clean growth-hormone-releasing peptide: five amino acids that pull the ghrelin lever to trigger a pulse of your own growth hormone, without the cortisol spike older peptides caused. Its evidence is largely preclinical, it's short-acting, and it's a research compound, not a medicine. The broader map is in growth-hormone secretagogues explained; it's most often discussed next to CJC-1295.