Muscle building
Compounds used to add or hold muscle.
The honest summary first: nothing on this page has been shown to build meaningful muscle in a healthy trained adult. What the compounds share is a plausible route to it — more growth hormone, more IGF-1, or a block on myostatin — and studies that stop short of measuring what people actually want measured.
The follistatin and myostatin compounds are the ones with the striking animal photographs, and they are also the ones with no human safety data worth the name. The growth hormone secretagogues have more human exposure but a smaller effect. IGF-1 variants sit in between and carry the most serious theoretical risks.
If you compete, treat this whole page as prohibited. Growth hormone secretagogues, IGF-1 analogs and myostatin inhibitors are all named on the WADA list, and several are detectable long after the last dose.
Bimagrumab is a monoclonal antibody that blocks the activin type II receptor, a signal that normally limits muscle. In plain terms: by releasing that brake it builds muscle while the body sheds fat, an unusual combination being studied with GLP-1 drugs. It is still experimental.
This is a blend of two growth-hormone signals: a GHRH analog that sets a steady base and a GHRP that adds a pulse. The CJC-1295 in these vials is almost always the no-DAC version, also called Mod GRF 1-29, because a short pulse is the whole point and the DAC version lasts about a week. In plain terms: together they nudge your body to release more of its own growth hormone than either alone, in one shot.
IGF-1 LR3 is a long-acting version of insulin-like growth factor 1, the hormone that growth hormone works through to build tissue. In plain terms: it directly drives muscle cells to grow and repair and stays active for hours, but it also drops blood sugar hard.
IGF-1 DES is a short, extra-potent version of insulin-like growth factor 1 that acts locally. In plain terms: injected into a specific muscle, it drives growth right there, then clears quickly.
Follistatin is a protein that binds and blocks myostatin, the body's natural brake on muscle growth. In plain terms: with the brake released, muscles can grow beyond their normal limit, an effect that is dramatic in animals but experimental in people.
MGF (mechano growth factor) is a variant of IGF-1 that muscles produce locally after intense exercise. In plain terms: it activates the stem cells that rebuild muscle, so it is injected near a worked muscle to speed repair.
PEG-MGF is mechano growth factor with a PEG coating that makes it last far longer in the body. In plain terms: it does the same muscle-repair job as MGF but on a less-frequent schedule.
ACE-031 (ramatercept) is a decoy receptor that soaks up myostatin and activin, the signals that limit muscle. In plain terms: by mopping up those brakes it lets muscle grow, but its development was paused over side effects.
BPC-157 is a synthetic chain of 15 amino acids based on a protective protein found in stomach acid. In plain terms: it seems to speed the body's own repair signals, especially for blood vessels and connective tissue, which is why people use it after injuries, though almost all evidence is from animals.
TB-500 is a synthetic fragment of thymosin beta-4, a natural protein involved in cell repair and movement. In plain terms: it is used to help muscles, tendons, and other tissue heal and to improve flexibility, though most evidence is from animals and most products are the fragment, not the full protein.
Apitegromab is an antibody that blocks myostatin, the signal your body uses to limit how much muscle it builds. It is being tested alongside tirzepatide, because a large share of the weight people lose on those drugs is muscle rather than fat. In plain terms: the idea is to keep the fat loss and lose less muscle with it. It is not approved for anything, and it is an antibody rather than a peptide.
Trevogrumab is an antibody that blocks myostatin, the signal that limits muscle growth. It is being tested alongside semaglutide for the same reason as apitegromab: about a third of the weight lost on semaglutide is muscle. In plain terms: it is an attempt to make weight loss come more from fat. It is not approved anywhere, and it is an antibody rather than a peptide.
GDF-8 is myostatin, a growth factor your body makes to limit how much muscle it builds. Animals and people with natural myostatin mutations develop unusually large muscles, which is why the molecule became famous.
FLGR242 is sold as a modified follistatin construct fused to an albumin-binding peptide, intended to inhibit myostatin for longer than follistatin does on its own. In plain terms: it is marketed as follistatin that lasts longer in the body.
Neither has a single published human trial, and sources give LR3's half-life as anywhere from 6 to 30 hours. There is an FDA approved IGF-1, and it is neither of these.
Both are sold for tendon and muscle repair. BPC-157's human trials were enemas for ulcerative colitis, and TB-500's trials did not even use TB-500.
Common questions
Do muscle building peptides actually work?
Evidence is thin for most of them. A few raise growth hormone or IGF-1 measurably, but changes in lean mass in humans are usually small and often come from studies that were not designed to measure muscle growth.
Are muscle building peptides the same as steroids?
No. Anabolic steroids act directly on androgen receptors. These peptides mostly work through the growth hormone or IGF-1 axis, which produces a different and generally weaker effect on muscle.
Are they banned in sport?
Most are on the WADA prohibited list, including growth hormone secretagogues and IGF-1 analogs. Assume any compound here is bannable if you compete in a tested sport.