GROWTH HORMONE AXIS / FIELD GUIDE
A Field Guide to GH-Secretagogue Research
Four peptides, one shared target: the pathway that tells the pituitary gland to release growth hormone. Here's what the published research actually shows about each — citations included, caveats never skipped.
CJC-1295
The long-acting GHRH analog that anchors this guide — a single dose keeps growth hormone elevated for days by binding directly to circulating albumin.
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CJC-1295 / Ipamorelin
The most widely discussed research combination in this space — pairing a GHRH analog with a selective ghrelin-receptor agonist for a larger GH pulse than either alone.
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Ipamorelin
A five-amino-acid secretagogue prized in the literature for one thing above all: it releases growth hormone without meaningfully raising cortisol or prolactin.
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Tesamorelin
The one FDA-approved compound in this guide — a GHRH analog cleared in 2010 for a specific form of abdominal fat accumulation, with the deepest clinical trial record of the four.
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This site is a field guide, not a storefront. It walks through four peptides that researchers study because they push on the same lever: the growth hormone (GH) axis, the signaling chain that runs from the brain to the pituitary gland to the liver. Growth hormone itself is released in pulses, mostly overnight, and it drives the liver to make IGF-1, a hormone tied to tissue repair, metabolism, and growth.
Each compound here nudges that pulse a different way. CJC-1295 and tesamorelin copy a natural signal called GHRH. Ipamorelin copies a different signal, the one that ghrelin (the "hunger hormone") uses. Combining the two signals, as in CJC-1295/Ipamorelin, is thought to produce a bigger GH pulse than either alone. None of these four is an over-the-counter supplement — three are unapproved research chemicals, and the fourth is a prescription drug for one specific medical condition. This guide describes what has actually been studied, in whom, and how far that evidence reaches.
What is the growth hormone axis?
The GH axis begins in the hypothalamus, which releases growth-hormone-releasing hormone (GHRH) toward the pituitary gland. GHRH binds the GHRH receptor on pituitary cells called somatotrophs, triggering a cascade (a Gs protein, cyclic AMP, protein kinase A) that causes those cells to synthesize and release growth hormone in discrete pulses — mostly during deep sleep. A second, independent pathway runs through the ghrelin receptor (GHS-R1a), normally activated by the stomach hormone ghrelin, which produces its own GH pulse through a different intracellular route (calcium signaling rather than cyclic AMP).
Once released, GH travels to the liver, where it stimulates production of insulin-like growth factor-1 (IGF-1) — the hormone most directly responsible for GH's downstream effects on tissue and metabolism. Compounds studied for the GH axis work by amplifying one or both of these upstream signals rather than supplying GH itself, which is the organizing idea behind this whole guide [1].
Four peptides, two mechanisms
Two of the four peptides here work through the GHRH receptor: CJC-1295 and tesamorelin. Both are modified analogs of hGRF, chemically stabilized to resist the enzyme (DPP-IV) that would otherwise break down natural GHRH within minutes [1][4]. CJC-1295's defining trick is a covalent bond to serum albumin (its "DAC," or Drug Affinity Complex, chemistry), which is why a single dose can elevate GH for six or more days and IGF-1 for over a week [4][7]. Tesamorelin is stabilized differently and dosed daily; it is the only member of this quartet with FDA approval, cleared in 2010 specifically for HIV-associated visceral fat accumulation [16].
Ipamorelin takes the other route. It is a five-amino-acid peptide that activates the ghrelin receptor (GHS-R1a) instead of the GHRH receptor, and its signature finding in the literature is selectivity: unlike older ghrelin-mimetic peptides, it releases GH without meaningfully raising cortisol or prolactin [15]. Because GHRH-receptor and ghrelin-receptor signaling are mechanistically independent, researchers have studied stacking the two — which is exactly what CJC-1295/Ipamorelin is: a GHRH analog paired with a selective ghrelin-receptor agonist, a combination whose rationale rests on older evidence that co-activating both receptors produces a larger signal than either pathway alone [10].
How this guide reads the evidence
The four compounds on this guide sit at very different points on the evidence spectrum, and this site says so plainly rather than smoothing it over. Tesamorelin has the deepest human trial record of the four, including a 2026 meta-analysis of five randomized controlled trials [8]. CJC-1295's human data are older and narrower — a handful of pharmacology studies in healthy volunteers from the mid-2000s, with no FDA approval and nothing larger since [3][4][5]. Ipamorelin's only placebo-controlled human trial, in postoperative patients, missed its primary endpoint [13]. And the CJC-1295/Ipamorelin combination itself has never been tested as a fixed pairing in any controlled study — its rationale is built by combining each compound's separate literature with older receptor-interaction work [10]. Where community reports diverge from the trial record, this guide labels them anecdotal and says so directly, on every compound page.