Widely sold for hair loss, and largely untested in humans. The comparison that matters.
Featured investigation
Every major peptide benefit claim, sorted by how strong the human evidence actually is.
Research
Better sleep and more energy are standard peptide selling points. No growth-hormone secretagogue has been tested with sleep laboratory measurement, and the one peptide with a large sleep trial works by a completely different route.
Copper peptides and topical retinoids are both sold for photoaged skin. One has several small trials, the other decades of large ones. What each has actually demonstrated, and the head-to-head trial nobody has run.
"FDA-approved" and "works" are different questions, and conflating them is how most peptide confusion starts. This explains the two independent axes — regulatory status and evidence level — with four worked examples.
Fake and counterfeit versions of semaglutide and tirzepatide are being sold online, sometimes with made-up pharmacy labels. Here is how the FDA says to recognize them and buy safely.
Compounded semaglutide is not the same as Ozempic or Wegovy. It is not FDA-checked, the shortage that made it common is over, and the FDA has linked it to dosing errors and hospital visits. Here is the plain version.
Growth-hormone peptides are sold almost entirely on muscle claims. No controlled trial has measured muscle with them. The one peptide with positive lean-mass data is the one nobody markets for it.
Explore by peptide
Synthetic gastric-derived pentadecapeptide
A synthetic 15-amino-acid peptide with a large animal literature on tendon, muscle and gut healing, almost no controlled human data, and no FDA approval.
Growth hormone-releasing hormone (GHRH) analogue
A synthetic GHRH analogue that raises growth hormone and IGF-1 in short human pharmacology studies. Development was discontinued; no outcome trials exist and it is not FDA-approved.
Dietary protein hydrolysate (mixture of collagen-derived di-, tri- and oligopeptides)
Food-grade hydrolysed collagen taken orally, with multiple randomised trials for skin hydration, joint discomfort and body composition — modest effects, mostly industry-funded, and no drug approval needed.
Naturally occurring copper-binding tripeptide
A naturally occurring copper-binding tripeptide with small human trials in topical skin care and wound healing, extensive gene-expression studies, and no drug approval.
Growth hormone secretagogue (ghrelin/GHS-R1a agonist), pentapeptide
A selective ghrelin-receptor agonist that stimulates growth hormone release. Early human studies exist; a post-operative ileus programme was discontinued for lack of efficacy. Not FDA-approved.
Melanocortin receptor agonist (cyclic heptapeptide, melanotan II metabolite)
Bremelanotide, marketed as Vyleesi, is an FDA-approved melanocortin agonist for hypoactive sexual desire disorder in premenopausal women. Its use in men and for erectile dysfunction is not approved.
GLP-1 receptor agonist (incretin mimetic), 31-amino-acid modified peptide
An FDA-approved GLP-1 receptor agonist with large randomised trials for type 2 diabetes, chronic weight management and cardiovascular risk reduction — the strongest evidence base of any peptide in this publication.
Synthetic fragment of thymosin beta-4 (actin-sequestering peptide)
A synthetic fragment marketed as thymosin beta-4. The full-length natural peptide has early human trials in wound healing and eye disease; the fragment sold as TB-500 has none.
Growth hormone-releasing hormone (GHRH) analogue
An FDA-approved GHRH analogue that reduces visceral abdominal fat in HIV-associated lipodystrophy. Widely discussed off-label for body composition and cognition, where evidence is much thinner.
Dual GIP/GLP-1 receptor agonist, 39-amino-acid modified peptide
An FDA-approved dual GIP and GLP-1 receptor agonist with large randomised trials showing the greatest weight loss of any approved incretin therapy, plus approvals for type 2 diabetes and obstructive sleep apnoea.
Explore by research area
Fat loss and lean mass claims are the most common reason people search for peptides. The evidence ranges from large approved-drug trials to zero human data, depending on the peptide.
Cognitive claims for peptides — focus, memory, neuroprotection — are almost entirely preclinical. GLP-1 drugs are the exception, with large Alzheimer's trials now reporting.
"Longevity" claims for peptides rest on animal lifespan studies and hormone-level surrogates. No peptide has human evidence of extending lifespan or healthspan.
A reader's guide to peptide research: study types, what animal models can and cannot tell you, common statistical traps, and how marketing misuses real papers.
Thymic peptides have a long, mixed history in immunology; the popular "immune-boosting" peptides sold online have little or no human evidence for immune outcomes.
GLP-1 and dual-incretin peptides have transformed metabolic medicine with large trials and FDA approvals; almost every other "metabolic" peptide claim rests on far weaker evidence.
What is known about the safety of approved peptides from their trials and labels, and why "no reported side effects" for unapproved peptides usually means "no one has looked".
What peptide research actually shows for tendon, ligament, muscle, gut and wound healing — mostly animal data, with a few small human studies and one approved topical use.
How the FDA classifies peptides — approved drugs, investigational agents, compounding-eligible substances, and "research use only" products — and why the categories matter for evidence and safety.
Bremelanotide (PT-141) is FDA-approved for hypoactive sexual desire disorder in premenopausal women; its use in men and for erectile dysfunction is not approved and rests on older, smaller studies.
Topical copper peptides and oral collagen peptides have small human trials for skin; hair-growth claims for peptides rest almost entirely on animal and cell studies.
Evidence system
Every page carries both labels. The matrix on the right plots each profiled peptide on both axes for its most-discussed use — and shows how often they disagree.
| Evidence ↓ / Regulatory → | FDA-approved for this use | Not FDA-approved |
|---|---|---|
| Established | ||
| Promising | ||
| Preliminary | ||
| Preclinical |
Comparison
BPC-157 vs TB-500
Comparison
CJC-1295 vs ipamorelin vs tesamorelin
Comparison
Semaglutide vs tirzepatide
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