Growth hormone peptides is a label for a mixed group of molecules that share one goal: getting the pituitary gland to release more of its own growth hormone rather than injecting growth hormone itself. They reach that goal through two different doors, and the door matters for everything else, from side effects to legal status.
This page sorts them by receptor and sets out the human evidence for each. What they did to muscle is covered separately in peptides for muscle growth.
Two receptors, one gland
The first door is the receptor for growth-hormone-releasing hormone, the signal the hypothalamus sends to the pituitary to start a pulse of growth hormone; sermorelin, tesamorelin and CJC-1295 are all built from that hormone's sequence.
The second door is the growth hormone secretagogue receptor, whose natural key is ghrelin, a hormone best known for hunger. In mice bred without that receptor, ghrelin no longer triggered either growth hormone release or eating, which established it as the receptor through which ghrelin does both [1].
That shared receptor is why appetite keeps turning up in the side-effect lists of ghrelin mimetics, and why the two families behave differently even when they reach the same pituitary. The same mouse study found that animals without the receptor were not dwarfs, suggesting that ghrelin amplifies growth hormone pulses rather than being essential to them, though that part is the authors’ interpretation rather than a direct measurement [1].
One practical consequence has been proposed for the ghrelin mimetics. Because they work through the body’s own pulsatile release and its feedback loops, a 2018 review argued they can avoid the very high growth hormone levels that injected hormone can produce [2]. The same review found few long-term, rigorously controlled studies and flagged rising blood sugar as a concern.
The molecules, side by side
| Molecule | Receptor | Human evidence | U.S. status |
|---|---|---|---|
| Sermorelin | GHRH | Small trials; once approved as GEREF | Compoundable |
| Tesamorelin | GHRH | Randomized trials in HIV lipodystrophy | Approved as Egrifta WR |
| CJC-1295 | GHRH | Dosing studies in healthy adults | FDA cites serious adverse events |
| Ipamorelin | Ghrelin | One dosing study, one phase 2 trial | 503B Category 2 |
| GHRP-2, GHRP-6 | Ghrelin | Limited | 503B Category 2 |
| MK-677 (not a peptide) | Ghrelin | Randomized trials in older adults | 503A and 503B Category 2 |
The GHRH analogs
Sermorelin is the first 29 amino acids of the natural hormone, and it was sold as GEREF, an injection approved for testing pituitary function and for treating growth hormone deficiency in children. The maker discontinued it, and in 2013 the FDA determined it was not withdrawn for safety or effectiveness reasons [6]. Whether it works without a needle is covered in sermorelin nasal spray.
Tesamorelin is a modified analog of the same hormone, and it has the strongest evidence in the group. In a trial of 412 adults with HIV and excess abdominal fat, 2 mg injected daily for 26 weeks cut visceral fat by 15.2%, against a 5.0% rise on placebo, and raised IGF-I by 81.0% [3].
Its current label, for Egrifta WR, limits it to reducing excess abdominal fat in adults with HIV and lipodystrophy, and states that it is not indicated for weight loss [7]. It warns of glucose intolerance, fluid retention and raised IGF-1. The full record is in the tesamorelin evidence review, and how it differs from the older GHRH analog is in tesamorelin vs sermorelin.
CJC-1295 was engineered to last far longer. In healthy adults, one injection raised growth hormone 2- to 10-fold for 6 days or more, with an estimated half-life of 5.8 to 8.1 days [4]. That long exposure is the design choice, and it is also the difference from the brief natural pulse the other analogs mimic. The FDA says it has identified serious adverse events with CJC-1295, including a raised heart rate and a systemic vasodilatory reaction [8].
The ghrelin mimetics
The ghrelin-receptor group began with small synthetic peptides such as GHRP-2 and GHRP-6, and ipamorelin is a later, five-amino-acid member of the group. The FDA lists GHRP-6 for effects on cortisol and rising blood glucose, and GHRP-2 for reports of serious events that include pancreatitis, though it notes causality has not been established [8].
Ipamorelin’s human record is a dosing study and a bowel-surgery trial, covered in the ipamorelin evidence review, with its safety record in ipamorelin side effects.
The best-studied drug on this receptor is not a peptide at all. MK-677, also called ibutamoren, is a pill. In 65 healthy adults aged 60 to 81, 25 mg a day raised growth hormone and IGF-I to young-adult levels and increased fat-free mass, but did not improve strength or function [5]. Fasting glucose rose and insulin sensitivity fell.
Where sleep fits
These peptides are widely marketed for sleep, and the natural releasing hormone has changed sleep stages in small human studies. Those studies, and the ones that found no benefit, are gathered in peptides for sleep.
What this means
Of the whole class, sermorelin is the one with a clear basis for compounding, the FDA's 2013 GEREF determination, and tesamorelin is the one with a current approval, for one narrow use. Every other molecule here is research-only, and none has an established human dose for muscle, sleep or aging.
Athletes face a flat rule: the 2026 World Anti-Doping Agency list prohibits GHRH and its analogs, including sermorelin, tesamorelin and CJC-1295, and the ghrelin mimetics, including ipamorelin and MK-677, at all times [10]. For approved options with human sleep data, start at the sleep goal page.