GHRP-2 vs Retatrutide vs Sermorelin

A three-way comparison to help you find the right peptide for your research goals.

GHRP-2

Growth Hormone Releasing Peptide 2 (GHRP-2) is considered one of the most potent GHRPs available. It provides strong GH release with moderate hunger increase compared to GHRP-6.

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Retatrutide

Retatrutide (LY3437943) is a first-in-class triple agonist peptide targeting GIP, GLP-1, and glucagon receptors simultaneously. Developed by Eli Lilly, it is currently in Phase 3 clinical trials and has demonstrated the highest weight loss of any obesity medication to date — up to 28.7% body weight reduction at 48 weeks. The triple-receptor mechanism represents the next evolution beyond dual agonists like tirzepatide.

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Sermorelin

Sermorelin is a synthetic analog of GHRH consisting of the first 29 amino acids of the natural hormone. It was previously FDA-approved for GH deficiency diagnosis and treatment in children.

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Side-by-Side Comparison

Aspect	GHRP-2	Retatrutide	Sermorelin
Dose Range	100 mcg–300 mcg	4 mg–12 mg	100 mcg–300 mcg
Frequency	3x daily	Less than daily	1x daily
Cycle Length	8–12 weeks	—	8–12 weeks
Route	subcutaneous	subcutaneous	subcutaneous
Mechanism	Binds to the ghrelin receptor (GHS-R) to stimulate GH release from the pituitary. Also has some direct effects on the hypothalamus. Causes less appetite increase than GHRP-6.	Retatrutide is a synthetic peptide that activates three incretin/metabolic hormone receptors: (1) GLP-1 receptor — appetite suppression, insulin secretion, delayed gastric emptying, (2) GIP receptor — enhanced insulin sensitivity, improved fat metabolism, (3) Glucagon receptor — increased energy expenditure, hepatic fat mobilization, thermogenesis. The glucagon receptor component is the key differentiator, adding an energy-expenditure mechanism absent from GLP-1 and dual GIP/GLP-1 agonists. The molecule uses a C20 fatty diacid for albumin binding, enabling once-weekly dosing.	Binds to GHRH receptors in the pituitary gland to stimulate natural GH production and release. Maintains the body's natural feedback mechanisms for GH regulation.
Typical Dosage	Typical dosing: 100-300mcg administered 2-3 times daily. Often stacked with GHRH peptides for enhanced GH release.	Phase 2 trial doses: 0.5 mg, 4 mg, 8 mg, and 12 mg weekly. The 12 mg dose produced maximum weight loss (28.7%). Phase 3 trials are evaluating doses up to 12 mg. Dose escalation schedule similar to other GLP-1s (start low, increase every 4 weeks). Final approved dosing not yet established — Phase 3 trials ongoing.	Typical dosing: 200-500mcg administered once daily, usually before bed. Some protocols use twice daily dosing.
Administration	Subcutaneous injection on an empty stomach. Can be used at bedtime to enhance natural GH pulse during sleep.	Subcutaneous injection, once weekly. Phase 3 trials use pre-filled single-dose pens. Not yet commercially available — estimated FDA approval ~2027-2028.	Subcutaneous injection, preferably at bedtime to work with natural GH release patterns. Can be combined with GHRPs for synergistic effects.
Side Effects	Moderate hunger increase, water retention, potential prolactin and cortisol elevation (less than GHRP-6), tingling sensations.	Phase 2 data: nausea (up to 25%), diarrhea (up to 22%), vomiting (up to 15%), constipation, decreased appetite. GI side effects were dose-dependent and generally mild-to-moderate. Lower rates of nausea compared to semaglutide, potentially due to GIP component. Increased heart rate observed at higher doses.	Generally well-tolerated. May cause injection site reactions, headache, flushing, or dizziness. Less side effects than direct GH administration.
Best For	Muscle Growth Fat Loss Sleep Quality	Weight Loss Diabetes Management	Muscle Growth Fat Loss Recovery & Healing Sleep Quality