Peptides for muscle growth and strength
12 peptides · 4 approved medicines
Seven of the twelve entries here are sold on the gray market, and nothing on this page is approved for building muscle in a healthy person anywhere. Most of them do raise growth hormone, and that part is measured and real. What happens next is the problem: where a study went on to measure muscle, strength or physical performance, it found no change. The clearest case is growth hormone itself — pooling 27 randomised comparisons in 303 fit young people, lean tissue rose and strength and exercise capacity did not improve. For several of the others nobody has ever measured it at all. The four approved medicines here are licensed for growth disorders, for a rare hormone deficiency in children, for a specific fat problem in HIV, and for an ultra-rare genetic disease — and the last of those was approved even though knee strength did not improve during its randomised trial. The twelfth is a food supplement, and most of the exercise evidence attached to it comes from studies that gave people a different compound — the building block the body converts into it — rather than the supplement itself.
- Approved medicine
IGF-1 (insulin-like growth factor 1)
Insulin-like growth factor 1 · Insulin-like growth factor-I
Category TherapeuticApproved as mecasermin for a rare growth disorder in children, and sold separately online as IGF-1 LR3 for muscle growth.
The approved use compares children with their own growth before treatment, not with a placebo group; the IGF-1 LR3 sold for muscle has never been given to a person in a published study.
- Approved medicine
Somatropin
Recombinant human growth hormone · rhGH
Category TherapeuticApproved for growth failure in children and growth hormone deficiency in adults, and promoted far beyond that for anti-ageing, fat loss and muscle.
Randomised trials support the approved uses; in healthy adults it shifted fat and lean tissue without improving strength, endurance or function.
- Approved medicine
SS-31 (elamipretide)
Elamipretide · Elamipretide hydrochloride
Category TherapeuticApproved in the United States to improve muscle strength in Barth syndrome, an ultra-rare inherited disease, and sold online as a mitochondria and anti-ageing peptide.
Its largest trials, in mitochondrial myopathy, heart failure and eye disease, all failed; the approval rests on a strength measure that did not move against a dummy injection.
- Approved medicine
Tesamorelin
Egrifta · Egrifta SV
Category TherapeuticApproved in the United States to shrink the deep belly fat of adults with HIV-related lipodystrophy, and promoted elsewhere for fat loss, muscle and anti-ageing.
Two large placebo-controlled trials measured the fat reduction; Europe's regulator judged the same data did not show any health benefit and never approved it.
- Still being tested in people
Ipamorelin
NNC 26-0161
Category Gray marketPromoted for muscle growth and recovery, although its human trials studied bowel recovery after surgery.
It reached mid-stage trials, but the programme ended and the results were never published.
- Still being tested in people
MK-677 (ibutamoren)
Ibutamoren · Ibutamoren mesylate
Category Gray marketPromoted for muscle growth, better sleep and slower ageing through higher growth hormone levels.
Trials raised the hormone every time and changed nothing measurable: no more strength, no better function, no effect on the diseases it was tested against.
- Tested in people, but barely
Carnosine
L-carnosine · beta-alanyl-L-histidine
Category SupplementSold as a supplement for ageing, exercise performance and eye health.
Blood sugar came down against a dummy capsule in two small trials, but an enzyme in blood destroys it within minutes, most of the exercise evidence is really about beta-alanine, and pooled autism trials found no difference from placebo.
- Tested in people, but barely
CJC-1295
CJC-1295 with DAC · CJC-1295 without DAC
Category Gray marketPromoted for muscle growth, strength and recovery through higher growth hormone levels.
Short studies measured hormone levels, but none showed more muscle, greater strength or faster healing.
- Tested in people, but barely
GHRP-2
Pralmorelin · Pralmorelin (INN)
Category Gray marketApproved in Japan only as a one-off injection for diagnosing growth hormone deficiency; promoted online for muscle, appetite and recovery.
It reliably releases growth hormone and demonstrably makes people eat more, but no study has ever measured muscle, strength or body fat in a person taking it.
- Tested in people, but barely
GHRP-6
Growth hormone-releasing peptide 6 · Growth hormone-releasing hexapeptide
Category Gray marketPromoted for muscle growth and for appetite, and sold as a research chemical.
Human studies measured hormones in blood for a couple of hours after a single dose; none tested it as a treatment for anything.
- Tested in people, but barely
Hexarelin
Examorelin · Examorelin (INN)
Category Gray marketPromoted for muscle growth and recovery through higher growth hormone levels.
The one study that gave it for 16 weeks and scanned people found no change in muscle, fat, bone or IGF-1.
- Tested in people, but barely
Sermorelin
Geref · sermorelin acetate
Category Gray marketSold by anti-ageing and hormone clinics, and online, to raise growth hormone for muscle, fat loss and sleep.
It was an approved medicine until 2009, but the uses it is sold for now were either never measured or measured once and found unchanged.