Body Composition

Body composition peptides primarily work by stimulating the body's own production and release of growth hormone (GH). Rather than injecting exogenous GH directly, these compounds act on the hypothalamic-pituitary axis to amplify natural GH secretion, preserving the pulsatile release pattern that is important for physiological function. The two main classes are GHRH analogs (Growth Hormone-Releasing Hormone analogs), which mimic the hypothalamic signal that tells the pituitary to release GH, and GHRPs (Growth Hormone-Releasing Peptides), which act on ghrelin receptors to trigger GH release through a separate, complementary pathway. When a GHRH analog and a GHRP are combined, their effects on GH output are synergistic — significantly greater than either alone.

Tesamorelin is the standout in this category as the only FDA-approved GH secretagogue, indicated for reducing visceral adipose tissue in HIV-associated lipodystrophy. CJC-1295 is a synthetic GHRH analog available in two forms: with and without the Drug Affinity Complex (DAC) that extends its half-life. The combination of CJC-1295 (without DAC) and Ipamorelin has become the gold standard pairing in clinical peptide therapy, offering robust GH elevation with a favorable side-effect profile. Ipamorelin is valued for its selectivity — it stimulates GH release without significantly raising cortisol or prolactin, unlike less selective GHRPs. The selectivity spectrum runs from Ipamorelin (most selective) through GHRP-2 and GHRP-6 to Hexarelin (strongest GH release but most side effects, including prolactin elevation).

MK-677 (Ibutamoren) occupies a unique position as an oral, non-peptide ghrelin mimetic. Its convenience makes it popular, though its long half-life means it produces a more sustained — rather than pulsatile — GH elevation, with potential implications for insulin sensitivity during extended use. AOD-9604 takes a different approach entirely: it is a modified fragment of the GH molecule (amino acids 177-191) that retains fat-metabolizing activity without the growth-promoting or diabetogenic effects of full-length GH.

This category has a relatively strong evidence base compared to many peptide classes. Tesamorelin has full FDA trial data, CJC-1295 and Ipamorelin have been studied in multiple clinical trials, and MK-677 has extensive human pharmacokinetic data. The key clinical considerations involve timing administration to complement natural GH rhythms, managing potential effects on blood glucose and insulin, and understanding that results typically develop over weeks to months of consistent use.