Peptides for muscle mass have two kinds of results in humans: a rise in growth hormone and IGF-1, or a measured gain in lean body mass. Tesamorelin, ACE-031 and a GHRH analogue related to sermorelin have the second, stronger kind of evidence. CJC-1295 and ipamorelin have a well-measured growth hormone release. Below we set out exactly what was measured for each molecule that bodybuilders buy most often.
Which peptides for mass have studies in humans?
Five molecules from the shop have studies in humans, and for three of them lean body mass was measured. The table shows what was measured and what the result was.
| Peptide | Who was studied | What was measured | Result |
|---|---|---|---|
| Tesamorelin | 5 randomised trials | lean body mass | plus 1.42 kg |
| ACE-031 | 48 healthy women | lean body mass | plus 3.3 percent after 29 days |
| GHRH 1-29 analogue | 19 people aged 55-71 | lean body mass | increase in men |
| CJC-1295 | healthy adults aged 21-61 | growth hormone and IGF-1 | IGF-1 1.5 to 3 times higher |
| Ipamorelin | healthy men | growth hormone | a pulse after every dose |
IGF-1 LR3, MGF, PEG-MGF and follistatin have no published studies of muscle gain in humans. Their mechanism and animal data are described in the guide on muscle peptides, the IGF-1 axis and myostatin.
What does raising growth hormone give?
Growth hormone given to healthy, athletic people increased lean body mass by 2.1 kg on average. That was the finding of a 2008 review of 44 papers covering 303 people with a mean age of 27. Strength and exercise capacity did not rise in these studies, and swelling and fatigue were more common.
This result explains what to expect from growth hormone peptides. A peptide raises the body's own growth hormone, and growth hormone adds lean mass. Strength is built by training, because growth hormone alone did not raise it in these studies.
What did the studies of CJC-1295 and ipamorelin show?
After one subcutaneous injection CJC-1295 raised growth hormone 2 to 10 times for at least 6 days. IGF-1 rose 1.5 to 3 times and stayed up for 9 to 11 days. After several doses given every week or every two weeks, IGF-1 stayed above baseline for up to 28 days.
In a 1999 study ipamorelin triggered a growth hormone pulse at each of five doses. The peak came after about 40 minutes, after which the level fell back to baseline. Muscle mass was not measured in any of these studies.
The two molecules act on the pituitary from two different sides, which is why they are paired. This is explained in the guide on why CJC-1295 and ipamorelin are combined most often. The results of ipamorelin alone are collected in the guide on what effects ipamorelin showed in studies.
How much lean mass did tesamorelin give?
Tesamorelin increased lean body mass by 1.42 kg on average in a 2026 meta-analysis of five randomised trials. In the same trials visceral fat fell by 27.7 cm² on the abdominal cross-section. Trunk fat decreased by 1.18 kg.
The trials were run in people with HIV and excess abdominal fat, because tesamorelin is an approved medicine for that indication. In the main 2007 trial a dose of 2 mg a day raised IGF-1 by 81 percent in 26 weeks. It is the only GHRH analogue approved as a medicine, as described in the guide on tesamorelin as the only GHRH analogue approved as a medicine.
The result for belly fat is broken down in a separate guide on what tesamorelin did to belly fat.
What did a GHRH analogue show in older people?
In a 1997 study 19 people aged 55 to 71 injected themselves with a GHRH 1-29 analogue every evening for 16 weeks. Growth hormone rose within 10 minutes of the injection and stayed up for 2 hours. IGF-1 rose after just 2 weeks.
In men lean body mass, insulin sensitivity and well-being increased. In women these changes did not occur, but skin thickened in both sexes. Sermorelin belongs to the same group of GHRH 1-29 analogues, as described in the guide on sermorelin and Mod GRF 1-29.
What is known about ACE-031 in humans?
After a single dose ACE-031 increased whole-body lean mass by 3.3 percent in healthy postmenopausal women. The 2013 study included 48 women, and the effect was measured 29 days after the injection. Thigh muscle volume on imaging rose by 5.1 percent at a dose of 3 mg per kilogram.
ACE-031 acts as a trap for myostatin, a protein that holds back muscle growth. A study in boys with Duchenne muscular dystrophy was, however, stopped because of nose and gum bleeding. Both sides of this molecule are described in the guide on follistatin and ACE-031.
What about recovery after training?
In bodybuilding BPC-157 and TB-500 are bought for tendons, joints and a faster return after injury. Their results come mainly from animal studies, and human data are scattered. The mechanism and state of research are collected in the guide on how recovery peptides work.
Are peptides for mass allowed in competition?
They are not. GHRH analogues, growth hormone secretagogues, IGF-1 and its analogues and MGF are on the prohibited list in class S2. The ban applies all year round, out of competition too. If you compete in a federation with doping control, read the guide on what the WADA list says about BPC-157 and TB-500.
Where to buy peptides for muscle mass?
All the molecules in the table are in the shop as vials of freeze-dried powder for dissolving. The cheapest start is CJC-1295 5 mg Bio-Peptide for 25 EUR. Ipamorelin 10 mg Bio-Peptide costs 40 EUR, and both in one vial come as Ipamorelin and CJC-1295 Combo Nouveaux for 40 EUR.
- Tesamorelin 10 mg Genheal: 50 EUR.
- Sermorelin 5 mg Bio-Peptide: 40 EUR.
- ACE-031 10 mg Bio-Peptide: 80 EUR.
Progress is best tracked by measuring IGF-1 and body composition, as described in the guide on how to measure peptide results. Matching a peptide to a training goal is covered in the guide on choosing peptides for your training goal. The products in the shop are material for laboratory research, not a medicine.
Frequently asked questions
Which peptides for muscle mass have studies in humans?
A gain in lean body mass was measured for tesamorelin, ACE-031 and a GHRH 1-29 analogue. CJC-1295 and ipamorelin have a measured rise in growth hormone.
How much lean mass does growth hormone give?
In a 2008 review of 44 papers, growth hormone gave healthy people 2.1 kg of lean body mass on average. Strength and exercise capacity did not rise in these studies.
How long does CJC-1295 work?
After one injection growth hormone was raised for at least 6 days, and IGF-1 for 9 to 11 days. The half-life was 5.8 to 8.1 days.
Does ACE-031 increase muscle mass?
A single dose of 3 mg per kilogram increased lean body mass by 3.3 percent in healthy women after 29 days. Thigh muscle volume rose by 5.1 percent.
Are peptides for mass banned in sport?
Yes. GHRH analogues, growth hormone secretagogues, IGF-1 and MGF are in class S2 of the prohibited list all year round.
Sources
- Liu H, Bravata DM, Olkin I et al. Systematic review: the effects of growth hormone on athletic performance. Annals of Internal Medicine, 2008, 148(10): 747-758. https://doi.org/10.7326/0003-4819-148-10-200805200-00215
- Teichman SL, Neale A, Lawrence B et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Journal of Clinical Endocrinology and Metabolism, 2006, 91(3): 799-805. https://doi.org/10.1210/jc.2005-1536
- Gobburu JV, Agersø H, Jusko WJ et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharmaceutical Research, 1999, 16(9): 1412-1416. https://doi.org/10.1023/a:1018955126402
- Badran AS, Helal A, Shata KS, Ayesh H. Body composition, hepatic fat, metabolic, and safety outcomes of Tesamorelin, a GHRH analogue, in HIV-associated lipodystrophy: A meta-analysis of randomized controlled trials. Obesity Research and Clinical Practice, 2026, 20(1): 2-12. https://doi.org/10.1016/j.orcp.2026.01.002
- Falutz J, Allas S, Blot K et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. New England Journal of Medicine, 2007, 357(23): 2359-2370. https://doi.org/10.1056/NEJMoa072375
- Khorram O, Laughlin GA, Yen SS. Endocrine and metabolic effects of long-term administration of [Nle27]growth hormone-releasing hormone-(1-29)-NH2 in age-advanced men and women. Journal of Clinical Endocrinology and Metabolism, 1997, 82(5): 1472-1479. https://doi.org/10.1210/jcem.82.5.3943
- Attie KM, Borgstein NG, Yang Y et al. A single ascending-dose study of muscle regulator ACE-031 in healthy volunteers. Muscle and Nerve, 2013, 47(3): 416-423. https://doi.org/10.1002/mus.23539
- Campbell C, McMillan HJ, Mah JK et al. Myostatin inhibitor ACE-031 treatment of ambulatory boys with Duchenne muscular dystrophy: Results of a randomized, placebo-controlled clinical trial. Muscle and Nerve, 2017, 55(4): 458-464. https://doi.org/10.1002/mus.25268
- List of prohibited substances and methods 2026 (Polish translation of the WADA list), Polish Anti-Doping Agency, class S2. https://antydoping.pl/wp-content/uploads/2025/12/2026_Lista-zabroniona.pdf