Growth-Hormone Peptides Explained: GHRH vs GHRP vs Secretagogues

Growth-hormone peptides are compounds that prompt your own pituitary to release more growth hormone, rather than injecting growth hormone directly. They split into a few categories that work through different receptors: GHRH analogs (sermorelin, CJC-1295, tesamorelin), GHRPs and ghrelin mimetics (ipamorelin), and an oral secretagogue (MK-677). Only one, tesamorelin, is FDA-approved, and only for a narrow indication; the rest are research-grade and not FDA-approved.

This article is a map of the category, not a protocol. Understanding the buckets is genuinely useful, because most confusion about "GH peptides" comes from treating very different compounds as one thing. Nothing here is a dosing guide or a recommendation to use any of them.

The system they all target

Every compound here acts on one hormonal axis, so it helps to start there. Your hypothalamus releases GHRH (growth-hormone-releasing hormone), which tells the pituitary to secrete growth hormone (GH) in pulses. GH then drives production of IGF-1 (insulin-like growth factor 1) in the liver, and IGF-1 mediates many of GH's downstream effects on tissue.

Two things modulate this system, and the drug classes map onto them. GHRH itself increases GH pulses. Ghrelin, a separate hormone acting on its own receptor (GHSR), also triggers GH release through a different pathway. Every "GH peptide" is essentially a way to push one of these two levers.

GH peptides are not HGH

This is the distinction that matters most, and it is the one marketing most often blurs. HGH (recombinant human growth hormone) is the hormone itself, injected directly. It produces a continuous, supraphysiologic elevation of GH, and that pattern is associated with side effects like carpal tunnel symptoms, fluid retention, glucose intolerance, and, with long-term misuse, acromegaly-like effects.

GH peptides work differently: they prompt your own pituitary to release GH. Because the pituitary is still in the loop, proponents argue the release stays pulsatile and is subject to the body's own feedback braking via somatostatin, giving a theoretical ceiling and a theoretical safety advantage over direct HGH. That argument is plausible mechanistically. It is not, however, validated by long-term human safety data, so it should be read as a hypothesis, not a guarantee.

It is worth being precise about why pulsatility is invoked so often. Native GH does not pour out at a steady level; it comes in bursts, particularly during deep sleep, and the body's downstream signaling is tuned to that rhythm. The argument for secretagogues is that, by nudging the natural system rather than overriding it, they preserve that burst pattern and let somatostatin (the brake) cap the response when GH gets high enough. The argument against complacency is twofold: first, this safety logic is mechanistic and unproven over years in humans, and second, not every secretagogue actually preserves pulsatility. A very long-acting GHRH analog, for example, can produce a sustained elevation that looks more like the continuous pattern proponents are trying to avoid. So "secretagogue" does not automatically mean "physiologic," and the detail matters.

The three categories

GHRH analogs

GHRH analogs are lab-made versions of growth-hormone-releasing hormone. They bind pituitary GHRH receptors and increase the amplitude of GH pulses, working with your machinery rather than replacing it. The main members:

• Sermorelin, the oldest, a fragment of the first 29 amino acids of GHRH with a short half-life of roughly 10 to 20 minutes. It was FDA-approved in the past before the products were withdrawn in 2008. See our sermorelin guide.
• CJC-1295, a modified GHRH analog that, in its DAC (drug affinity complex) version, binds albumin and stretches the half-life to roughly 6 to 8 days. The CJC-1295 guide covers the important DAC versus no-DAC split.
• Tesamorelin, the one FDA-approved member, discussed below.

GHRPs and ghrelin mimetics

GHRPs (growth-hormone-releasing peptides) and ghrelin mimetics bind the ghrelin receptor (GHSR) rather than the GHRH receptor, triggering GH release through a separate pathway. Ipamorelin is the community favorite here, valued for being selective: it stimulates GH with relatively little effect on cortisol, prolactin, or appetite, unlike older GHRPs such as GHRP-2 and GHRP-6. Our ipamorelin guide goes deeper.

Because GHRH analogs and ghrelin mimetics act on different receptors, the two are often combined (most commonly CJC-1295 with ipamorelin) on the theory that the two pathways produce a larger, synergistic GH pulse together. That rationale is mechanistic; there are essentially no combined human trials proving it.

Oral secretagogues

MK-677 (ibutamoren) is the odd one out: it is not a peptide at all, but an orally active small molecule that mimics ghrelin and binds the same GHSR receptor. Being oral makes it convenient (no injection), and it happens to have more published human data than most injectable peptides here, including a 12-month trial in older adults. That data is sobering, though: it showed a small lean-mass gain but no improvement in strength or function, alongside higher fasting glucose and worsened insulin sensitivity. The MK-677 guide covers this honestly.

How the categories compare

The table below is a conceptual map, not a dosing chart.

Category	Mechanism	Examples	Evidence and approval status
GHRH analogs	Bind GHRH receptor; raise GH pulse amplitude	Sermorelin, CJC-1295, tesamorelin	Tesamorelin FDA-approved (HIV lipodystrophy only); others not approved, mostly preclinical or early human data
GHRPs / ghrelin mimetics	Bind ghrelin receptor (GHSR); trigger GH release	Ipamorelin	Not FDA-approved; very limited human data
Oral secretagogues	Bind ghrelin receptor; orally active	MK-677 (ibutamoren)	Not FDA-approved; more human data than most, with documented metabolic side effects

All of the non-tesamorelin compounds are also banned in sport. The WADA 2026 Prohibited List names CJC-1295, ipamorelin, tesamorelin, sermorelin, and MK-677 as prohibited at all times under category S2 (WADA 2026). If you are a tested athlete, every one of these is disqualifying.

Tesamorelin: the lone approval

Tesamorelin (brand name Egrifta) is worth singling out because it is the one genuinely FDA-approved member of this family. It is a GHRH analog approved in November 2010 for reducing excess abdominal fat in adults with HIV-associated lipodystrophy, with real randomized-controlled-trial evidence showing roughly a 15 to 18 percent reduction in visceral fat versus placebo in that population (FDA Egrifta label; Theratechnologies).

The crucial caveat: that approval is narrow. Using tesamorelin for general body recomposition or anti-aging in people without HIV is off-label, and the trial evidence does not automatically transfer to that use. Approval for one indication is not a blanket endorsement. Our tesamorelin and visceral fat article covers the distinction in detail.

Why category matters more than hype

The practical payoff of understanding these buckets is that it stops you comparing apples to oranges. A short-acting GHRH analog, a long-acting one, a ghrelin mimetic, and an oral non-peptide all "raise GH," but they do so with different receptors, half-lives, dosing rhythms, side-effect profiles, and legal footing.

It also reframes the central question. The interesting debate is rarely "which GH peptide is best," because the human outcome evidence is thin for nearly all of them. The honest framing is that raising GH and IGF-1 is well established, while the leap to "meaningfully and safely changes your body over years" is not. A shared class concern across every compound here is that raising IGF-1 could, in theory, stimulate growth of a pre-existing cancer, which is one reason providers screen carefully before considering any of them.

The class also shares a recognizable set of side effects, because they all push on the same axis. Fluid retention, joint aches, carpal-tunnel-like numbness and tingling, and rises in blood glucose are reported across GHRH analogs and ghrelin mimetics alike, and they trace back to the GH and IGF-1 elevation the compounds are designed to produce. The MK-677 trial data is instructive here: it raised IGF-1 and added a little lean mass, but it also worsened insulin sensitivity and raised fasting glucose without improving strength or function. That is the cautionary shape of the whole category, hormone numbers move, and the side effects that accompany them move too, while the outcomes people actually want remain unproven.

What to ask a provider

Because none of this is a casual supplement decision, any consideration of a GH peptide belongs with a licensed clinician. Useful questions:

• Which category and specific compound is being considered, and what is its actual evidence base?
• What screening, including malignancy history and glucose status, should happen first?
• Is the compound FDA-approved for my situation, or is this off-label or research-grade use?
• What does the current FDA compounding and WADA status mean for me?

Where Myo fits

Different GH-peptide categories mean different dosing cadences and pharmacokinetic behavior: a multi-day-half-life GHRH analog, a short-acting ghrelin mimetic, and an oral secretagogue are three different routines. If a provider prescribes a protocol, Myo's medication-level visualizer and reminders adapt to whichever compound and schedule you are actually on, and the reconstitution calculator handles the concentration math when an injectable vial needs mixing.

For anyone whose real goal is body composition, the more important point is that GH peptides are a small, unproven adjunct next to the proven drivers. Our complete guide to GLP-1 and muscle loss lays out how protein and resistance training, the things that actually move lean mass, do the heavy lifting, and Myo trends those alongside any provider-directed peptide so you can see whether anything is genuinely changing.

The bottom line: GH peptides are a family of compounds that push your own GH release through one of two receptor pathways. Tesamorelin is the lone FDA-approved member, for one narrow use; the rest are research-grade, banned in sport, and thin on human outcome evidence. Know the category, and keep any use with a provider.

References

• FDA. Egrifta (tesamorelin) Prescribing Information. https://www.fda.gov
• Theratechnologies / Contagion Live. FDA Approves F8 Formulation of Tesamorelin for HIV-Associated Lipodystrophy. https://www.contagionlive.com/view/fda-approves-f8-formulation-of-theratechnologies-tesamorelin-for-hiv-associated-lipodystrophy
• Nass R et al. (2008). Effects of an oral ghrelin mimetic (MK-677) on body composition in healthy older adults. Ann Intern Med.
• WADA. 2026 Prohibited List. https://www.wada-ama.org/en/prohibited-list
• Lexology. FDA 503A Peptide Update. https://www.lexology.com/library/detail.aspx?g=2e55b76a-3173-4e04-beda-bf021202f18d