# How Ipamorelin Works in the Research > What does ipamorelin peptide do? How ipamorelin works — the ghrelin receptor, the selective GH pulse, the IGF-1 axis, and how it compares to sermorelin, tesamorelin, and CJC-1295. Cited. One receptor, one selective pulse — and how that pulse differs from the GHRH peptides people compare it to. ## The gist So what does ipamorelin peptide do, mechanically? It pushes one specific button. Your pituitary gland has a receptor — GHS-R1a, the same one the hunger hormone ghrelin uses — and when ipamorelin docks onto it, the gland fires off a pulse of growth hormone (GH) [1]. That's the whole core action. The clever part is *selectivity*: older peptides hit the same button but also set off cortisol (stress) and prolactin; ipamorelin hits it cleanly, GH only [1]. Growth hormone then signals the liver to make IGF-1, a growth-and-repair messenger — though in short studies the IGF-1 rise doesn't always show up [4]. Because ipamorelin and the GHRH-type peptides (sermorelin, tesamorelin, CJC-1295) press *different* buttons that both raise GH, people pair them. Below: the receptor story, the IGF-1 axis, and how ipamorelin compares to its cousins. ## What is ipamorelin peptide? Ipamorelin peptide is a wholly synthetic pentapeptide — five amino acids, sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2 — designed as the first *selective* growth hormone secretagogue [1]. It was built from the older peptide GHRP-1 by removing a central dipeptide, and two of its amino acids are D-form residues that resist enzyme breakdown. Functionally, it is a ghrelin mimetic: it imitates the body's hunger hormone at the GHS-R1a receptor to trigger GH release, but unlike ghrelin or earlier GHRPs, it does so without meaningfully raising cortisol or prolactin [1]. ## The receptor and the pulse Ipamorelin binds GHS-R1a on pituitary somatotrophs (GH-producing cells) and opens a Gq/PLC calcium signal that releases stored GH [1]. Two details define how it works. First, selectivity: in rats and swine it matched GHRP-6's GH potency yet held cortisol and ACTH at baseline even above 200× the GH ED50 [1]. Second, the action is at the *release* step, not gene expression — in seabream pituitary cells, ipamorelin drove dose-dependent GH secretion with no change in GH transcription out to 48 hours [7]. The cell empties its GH stores in a pulse; it doesn't ramp up production. ## Down to IGF-1 — and why it doesn't always rise Growth hormone does much of its work through IGF-1, made by the liver in response to GH. But the GH pulse and the IGF-1 level don't always move together over short windows. In rats given ipamorelin for 15 days, bone growth rose dose-dependently with *no* measurable change in total IGF-1 [4] — part of the effect was local to the GH pulse. Over longer, sustained dosing, the axis does lift IGF-1: a 30-day infusion of the class cousin GHRP-2 held IGF-1 and its binding proteins elevated in older adults without the response fading [8]. So 'does ipamorelin raise IGF-1?' depends on how long and how steadily the GH axis is driven. ## Ipamorelin vs sermorelin Ipamorelin vs sermorelin is a comparison of two different receptors that both raise GH. Sermorelin is a GHRH analog — it mimics growth-hormone-releasing hormone and acts on the GHRH receptor through a cAMP pathway. Ipamorelin is a GHRP that acts on the ghrelin receptor (GHS-R1a) through a calcium pathway [1]. Because the two pathways are separate and complementary, GHRP-plus-GHRH combinations show greater GH output than either alone in related-peptide studies [9][10]. The practical contrast: sermorelin nudges the GHRH 'go' signal; ipamorelin adds a selective ghrelin-receptor pulse on top — and crucially does so without the cortisol older GHRPs raised [1]. ## Ipamorelin vs tesamorelin Ipamorelin vs tesamorelin pits a ghrelin-receptor GHRP against a GHRH analog, much like the sermorelin comparison — they act on different receptors. Tesamorelin is a stabilized GHRH analog acting on the GHRH receptor; ipamorelin acts on GHS-R1a, the ghrelin receptor, to fire a selective GH pulse [1]. The two mechanisms are complementary rather than interchangeable, which is again why GHRP+GHRH pairings exceed the additive GH response in class-level studies [9][10]. One mechanistic distinction worth noting on the ipamorelin side: its GH release survived even a glucocorticoid load in rats, with IGF-1 raised in combination [14] — a robustness feature of the ghrelin-receptor route. ## What is cjc 1295 ipamorelin? What is cjc 1295 ipamorelin? It is the pairing of a GHRH analog (CJC-1295) with the selective GHRP ipamorelin — two peptides that raise GH through two different receptors. CJC-1295 lifts the GHRH 'go' drive; ipamorelin adds a clean ghrelin-receptor GH pulse [1]. The rationale for combining them is the complementary-pathway synergy shown in related-peptide human and animal studies [9][10]. The combination itself has no published human outcome trial — what's documented is the pharmacology of its two halves, not a study of the two together. --- An optimistic, plain-English ordering of the ipamorelin record — the selective GH pulse logged where the studies confirm it, the cortisol and prolactin pathways left dark, the lone failed human trial kept in full view, and the community reports walled off as anecdote; a reading console pointed at the science, never a clinic, and nothing here dosed, prescribed, or sold.