What is Ipamorelin? Mechanism, Benefits & Dosage Guide
Summary
Ipamorelin is a pentapeptide ghrelin receptor agonist that selectively stimulates pulsatile growth hormone (GH) release without measurable ACTH/cortisol increase in animal models, and produces short-duration GH action in humans (peak ≈ 40 minutes; peptide half-life ≈ 2 hours).
Substance Properties
What is Ipamorelin?
Ipamorelin is a selective growth hormone secretagogue (GHS) that activates the GHSR-1a receptor (ghrelin receptor) to trigger GH release while leaving other pituitary axes (ACTH/cortisol) intact in animal models. Early pharmacological work compared this selectivity with GHRP-6 and GHRP-2: only ipamorelin avoided ACTH/cortisol increases even at very high doses in pigs.
How it creates a GH 'pulse'
In healthy volunteers, brief infusions produced a single GH episode peaking around 0.67 hours (~40 minutes) with peptide half-life near 2 hours — compatible with a short, physiological pulse returning to baseline. This profile suits protocols respecting natural GH pulsatility.
Selectivity vs. older GHRPs
Classic GHRPs (e.g., GHRP-6, hexarelin) can increase ACTH, cortisol, and prolactin, especially intravenously or at high exposure, while ipamorelin shows minimal ACTH/cortisol effects in animal tests even at doses >200× the ED50 for GH — a significant distinction for interpreting endocrine 'noise' in experiments.
Comparison with CJC-1295, GHRP-6, and MK-677
Ipamorelin produces short, targeted GH pulses. CJC-1295 (DAC) provides sustained GH/IGF-1 elevation for days-weeks. MK-677 (ibutamoren) is an oral GHS that increases 24-hour GH/IGF-1 with increased appetite. Each has a different temporal and endocrine profile.
Importance of administration timing
In adults, 60–70% of daily GH secretion concentrates after sleep onset during slow-wave phase. Researchers sometimes align short-acting GHS administration at times that don't blunt natural nocturnal pulses (educational perspective). The goal is support rather than 'flattening' of physiological rhythms.
Related Guides
Frequently Asked Questions (FAQ)
Does Ipamorelin increase cortisol?
In animal models, Ipamorelin shows minimal effect on ACTH/cortisol even at very high doses. This selectivity differentiates it from older GHRPs.
How fast does it work?
In human studies, GH peak occurs approximately 40 minutes after administration, with a peptide half-life of ~2 hours.
Can it be combined with GHRH analogues?
In research literature, combining GHS (like Ipamorelin) with GHRH (like CJC-1295 no DAC) is studied for potential synergistic GH increase based on different but complementary mechanisms of action.
References & Studies
- Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561.
- Jimenez-Reina L et al. Ipamorelin revisited: GH secretagogue selectivity. J Endocrinol Invest. 2002;25(1):22-28.
Disclaimer
This article is exclusively educational for researchers. It does not constitute medical advice.
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