The short answer: GHRH analogs and growth hormone secretagogues (GHS) both get the pituitary to release more of your own growth hormone, but they do it through two different receptors. GHRH analogs like sermorelin, CJC-1295 and tesamorelin copy growth hormone-releasing hormone and hit the GHRH receptor. Secretagogues like ipamorelin and MK-677 copy ghrelin, the "hunger hormone", and hit the ghrelin receptor, GHS-R1a.
That's why "GH peptides" isn't one bucket. The class tells you which lever a compound pulls before anything else about it matters.
Status as of October 25, 2026: of the compounds named here, only tesamorelin (Egrifta WR) is an FDA-approved drug on the market, for one use in adults with HIV. Sermorelin's approvals were withdrawn in 2009. CJC-1295, ipamorelin and MK-677 have never been FDA-approved. This post describes what the research and FDA records say. It isn't medical advice.
Updated October 25, 2026: expanded from the June 5 email with the receptor names, the pairing research, the appetite note, current FDA status for each compound and sources. Sales copy from the original email was removed.
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What is the difference between GHRH and GHS?
They're two separate signals to the same gland. GHRH comes from the hypothalamus and binds the GHRH receptor on the pituitary. Ghrelin, which comes mainly from the stomach, binds a different receptor, and synthetic secretagogues copy it.
The GHRH side is the older story. The Egrifta label describes it plainly: GHRH "acts on the pituitary somatotroph cells to stimulate the synthesis and pulsatile release of endogenous growth hormone," and tesamorelin "binds and stimulates human GRF receptors with similar potency as the endogenous GRF" (Egrifta WR label, rev. 3/2025). GRF and GHRH are two names for the same hormone.
The GHS side was found backwards. Chemists built small synthetic molecules that released growth hormone before anyone knew what they were acting on. In 1996 a Merck team cloned their target, a receptor in the pituitary and hypothalamus, and noted that the secretagogues seemed to "mimic an undiscovered hormone" (Howard et al., Science, 1996). Three years later a Japanese group found that hormone in the stomach: a 28-amino-acid peptide they named ghrelin, from a root meaning "grow" (Kojima et al., Nature, 1999).
The two pathways really are separate. In a small study of healthy men, researchers wore out the pituitary's response to GHRH with a long infusion. A fresh dose of GHRH then did nothing, but a GHS-type peptide still released growth hormone (Robinson et al., 1992).
GHRH vs GHS at a glance
GHRH analogs | Growth hormone secretagogues (GHS) | |
|---|---|---|
Copies | Growth hormone-releasing hormone (from the hypothalamus) | Ghrelin (mainly from the stomach) |
Receptor | GHRH receptor (GHRH-R) on the pituitary | Ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus |
Examples in research | Sermorelin, CJC-1295, tesamorelin | Ipamorelin, MK-677 (ibutamoren) |
How given in trials | Injection | Ipamorelin: IV infusion. MK-677: by mouth |
Side note | No appetite signal | Ghrelin raises appetite; appetite increase was the top side effect in a 2-year MK-677 trial |
FDA status | Tesamorelin approved (one use). Sermorelin withdrawn 2009. CJC-1295 never approved | None on the market. Ipamorelin and MK-677 never approved |
Sources: Egrifta WR label, Howard 1996, Gobburu 1999, Nass 2008, Federal Register, Mar 4, 2013, FDA safety-risk list, Apr 2026.
Is MK-677 a peptide?
No. MK-677, also called ibutamoren, is a small-molecule drug that copies ghrelin's action, and in trials it was taken by mouth once a day (Chapman et al., 1996). It gets lumped in with "GH peptides" because it works on the same receptor as ipamorelin, but it isn't built from amino acids.
Ipamorelin is a peptide, five amino acids long. Its developers at Novo Nordisk called it "the first selective growth hormone secretagogue" because, in pigs, it released growth hormone without the cortisol and ACTH spikes seen with older GHS peptides like GHRP-6 (Raun et al., 1998). That "clean" reputation comes from that animal work plus a small dose study in healthy men (Gobburu et al., 1999).
Why are GHRH and GHS peptides often paired?
Because lab studies found the two signals together release far more growth hormone than either one alone. That's the whole logic behind combinations like CJC-1295 with ipamorelin.
The idea traces to Cyril Bowers, who helped develop the first GHS peptides. In rat studies, his group described a "complementary, rather dramatic synergistic interaction" between GHS-type peptides and GHRH, and concluded it supported "the independent actions of these compounds" (Bowers et al., 1991). Decades later, a study of 47 men aged 18 to 74 opened with the same point: "Marked stimulation of pulsatile GH secretion is achieved via GHRH-GHRP synergy." It also found the effect got weaker with age and with more belly fat (Veldhuis and Bowers, 2009).
The word "pulsatile" matters here. Growth hormone is released in bursts, not a steady drip. In older adults, MK-677 raised the height of those bursts without changing how many there were (Chapman et al., 1996). Neither class replaces growth hormone. Both work on the body's own release pattern.
One honest caveat. The synergy research used lab infusions of natural GHRH with research peptides like GHRP-2. It wasn't a trial of the CJC-1295 and ipamorelin combination sold online. I couldn't find a published trial of that combination.
Does ipamorelin or MK-677 increase appetite?
The GHS class works on the ghrelin receptor, and ghrelin is a hunger signal. So appetite is the obvious side note.
In a small double-blind study, healthy volunteers given IV ghrelin ate more at a free-choice buffet than on saline, every one of them, by an average of 28%. The authors called ghrelin "the first circulating hormone demonstrated to stimulate food intake in man" (Wren et al., 2001).
In a 2-year trial of MK-677 in 65 healthy adults aged 60 to 81, "the most frequent side effects were an increase in appetite that subsided in a few months" and mild, temporary swelling in the legs and muscle pain. Fasting blood sugar went up and insulin sensitivity went down (Nass et al., 2008). Ipamorelin was designed to be more selective, but its human data are too thin to say how it compares on appetite.
GHRH analogs don't act on this receptor, so the hunger signal isn't part of their story. They have their own label warnings, such as blood sugar and IGF-1 levels for tesamorelin (Egrifta WR label).
Are CJC-1295, ipamorelin and MK-677 FDA approved?
No. Of the five compounds in this post, only tesamorelin is an approved drug on the market today, and only for one condition. Here's where each one stands as of October 25, 2026.
Tesamorelin (GHRH). Approved as Egrifta, now Egrifta WR, "for the reduction of excess abdominal fat in HIV-infected adult patients with lipodystrophy" (label). Full rundown: tesamorelin explained.
Sermorelin (GHRH). Approved as Geref in 1990 and 1997. The approvals were withdrawn in 2009 at the maker's request, and FDA later found it was "not withdrawn for reasons of safety or effectiveness" (Federal Register, 2013). How the two GHRH drugs compare: sermorelin vs tesamorelin.
CJC-1295 (GHRH). Never approved. FDA's compounding safety page says it "has identified serious adverse events associated with CJC-1295 including increased heart rate and systemic vasodilatory reaction" and that "available clinical data are limited" (FDA, Apr 2026).
Ipamorelin (GHS). Never approved. Its one patient trial, for bowel function after surgery, didn't beat placebo on its main measure (Beck et al., 2014). FDA lists it as a safety risk for outsourcing-facility compounding, citing immune-reaction risk and a published report of "serious adverse events including death" when it was given by IV for gut motility (FDA).
MK-677 / ibutamoren (GHS). Never approved. It's on FDA's Category 2 list, the "significant safety concerns" category, for pharmacy compounding (FDA nominations list, updated May 14, 2026). FDA cites "the potential for congestive heart failure in certain patients" and a hip-fracture trial that "was terminated early due to a potential safety signal of congestive heart failure."
One footnote for the GHS class: FDA did approve one ghrelin-receptor drug, macimorelin (Macrilen), in 2017, but only as a diagnostic test for adult growth hormone deficiency. FDA's database now lists it as discontinued (Drugs@FDA).
What about the interim peptide policy in the news? HHS sent an "Interim Access Policy for Compounding Using Certain Peptides" to the White House on October 14. As of this update it hasn't been issued and its list isn't public (Holland & Knight, Oct 2026). The compounding status tracker will show the list the day it publishes.
CJC-1295 vs ipamorelin: which is better?
That question doesn't have a research answer. They've never been compared head to head, and they aren't competitors in the first place. One is a GHRH analog, the other a ghrelin mimic, so they act on different receptors.
The better first question is the one the original email asked: which lever does a compound pull? Know the class, and you know the receptor, the side effects that come with it, and which other compounds it's actually similar to. How these classes show up in the popular stacks is covered in your GH stack, explained honestly, and what the evidence behind the tesamorelin-plus-ipamorelin pairing looks like is in tesamorelin and ipamorelin: what the evidence covers.
Got a compound you can't place in either class? Reply and tell me which one, and I'll add it to this page.
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