MK-677 (Ibutamoren)
Overview
An orally bioavailable, non-peptide growth hormone secretagogue that mimics the action of ghrelin at the GHS-R1a receptor. MK-677 stimulates sustained GH and IGF-1 elevation for up to 24 hours after a single oral dose without affecting cortisol levels. Its long duration of action and oral availability distinguish it from injectable GH secretagogues, and it preserves the pulsatile pattern of GH release.
Key Research Findings
Phase II trials showed significant increases in GH, IGF-1, and lean body mass. Two-year study in elderly adults demonstrated reversal of age-related GH decline and improvements in body composition and bone mineral density (Nass et al., J Clin Endocrinol Metab, 2008). Common side effects include increased appetite, mild edema, and transient insulin resistance.
Oral
In Clinical Trials
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CJC-1295
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Ipamorelin
In Clinical TrialsA highly selective growth hormone secretagogue that acts on ghrelin/GHS receptors in the pituitary gland to stimulate GH release. Unlike other GH secretagogues, ipamorelin does not significantly affect ACTH, cortisol, or prolactin levels, making it one of the most specific GH-releasing peptides. It works synergistically with GHRH analogs like CJC-1295.
Sermorelin
FDA ApprovedA synthetic 29-amino acid analog of GHRH representing the shortest fully functional fragment of the native 44-amino acid hormone. Sermorelin stimulates the pituitary to produce and release growth hormone through the natural GHRH receptor pathway, preserving the hypothalamic-pituitary feedback axis. It maintains physiological pulsatile GH secretion patterns.
Tesamorelin (Egrifta)
FDA ApprovedA synthetic GHRH analog consisting of the 44-amino acid sequence of human GHRH with a trans-3-hexenoic acid modification at the N-terminus to improve stability. Tesamorelin specifically targets visceral adipose tissue reduction by stimulating lipolysis through GH-mediated pathways. It is the only FDA-approved treatment for HIV-associated lipodystrophy.