Human Growth Hormone (HGH) vs Retatrutide
A detailed comparison to help you understand the differences and choose the right peptide for your research goals.
Human Growth Hormone (HGH)
Human Growth Hormone (somatropin) is a 191-amino acid protein identical to naturally produced GH. FDA-approved for growth hormone deficiency, Turner syndrome, and other conditions. Widely used off-label for anti-aging and performance.
Full details →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.
Full details →Side-by-Side Comparison
| Aspect | Human Growth Hormone (HGH) | Retatrutide |
|---|---|---|
| Dose Range | 200 mcg–2 mg | 4 mg–12 mg |
| Frequency | 1x daily | Less than daily |
| Cycle Length | 12–24 weeks | — |
| Route | subcutaneous | subcutaneous |
| Mechanism | Binds to GH receptors throughout the body, stimulating IGF-1 production in the liver. Promotes protein synthesis, fat metabolism, and cellular regeneration across multiple tissues. | 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. |
| Typical Dosage | Medical: 0.1-0.3mg/kg/week divided into daily doses. Anti-aging: 1-2 IU daily. Performance: 2-6 IU daily, sometimes higher. | 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. |
| Administration | Subcutaneous injection, preferably at night to mimic natural pulsatile release. Rotate injection sites. Store refrigerated. | Subcutaneous injection, once weekly. Phase 3 trials use pre-filled single-dose pens. Not yet commercially available — estimated FDA approval ~2027-2028. |
| Side Effects | Joint pain, water retention, carpal tunnel syndrome, potential insulin resistance, and acromegaly features with long-term high doses. | 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. |
| Best For |
Key Differences
Unique to Human Growth Hormone (HGH):
Unique to Retatrutide:
Key Studies
Human Growth Hormone (HGH)
- Transgenic Artifacts Caused by Passenger Human Growth Hormone.
Trends in endocrinology and metabolism: TEM, 2018
- [Human growth hormone and Turner syndrome].
Anales de pediatria (Barcelona, Spain : 2003), 2017
- Significance of the disulphide bonds of human growth hormone.
Endokrynologia Polska, 2013
Retatrutide
- Retatrutide in type 2 diabetes mellitus and obesity: an overview.
Expert review of clinical pharmacology, 2026
- Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials.
Diabetes, obesity & metabolism, 2026
- Rationale, design and baseline characteristics of the TRANSCEND-CKD trial of retatrutide in patients with chronic kidney disease.
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association, 2026
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