Ipamorelin, the first selective growth hormone secretagogue — VialBase Research
high
- Ipamorelin selectively releases GH without affecting cortisol or prolactin
- First GH secretagogue with true selectivity for GH release
- Dose-dependent GH release with no effect on ACTH or cortisol
Summary
This foundational study established ipamorelin as the first truly selective growth hormone secretagogue. Unlike other GH-releasing peptides (GHRP-6, GHRP-2, hexarelin), ipamorelin stimulates GH release without significantly affecting cortisol, ACTH, or prolactin levels, even at high doses.
Key Findings
- Ipamorelin releases GH with potency similar to GHRP-6
- Does NOT increase cortisol or ACTH secretion (unlike GHRP-6 and GHRP-2)
- Does NOT significantly increase prolactin levels
- Selectivity maintained even at doses 200x the effective GH-releasing dose
- GH release is dose-dependent and reproducible
- Acts through the ghrelin/GHS receptor (GHS-R1a) at the pituitary
Methodology
In-vivo studies in swine comparing ipamorelin with GHRP-6 and GHRH. Intravenous bolus dosing at multiple dose levels. GH, cortisol, ACTH, and prolactin measured via serial blood sampling. Selectivity assessed by comparing hormone profiles across dose ranges.
Limitations
- Animal study (swine) — selectivity needs confirmation in human dose-response studies
- Single-dose pharmacology — no chronic dosing data
- No body composition or functional outcomes assessed
- Ghrelin receptor agonism means potential appetite stimulation (not assessed)
- Commercial development for ipamorelin not pursued to regulatory approval
Relevance to Content
The defining paper for ipamorelin’s key selling point: selectivity. This is why ipamorelin is preferred over older GHRPs in peptide therapy — it releases GH without the cortisol spikes or prolactin elevation that other GH secretagogues cause. Essential citation for any content comparing GH secretagogues or explaining why ipamorelin is favored.
See Also
- Parent compound: Ipamorelin