What ipamorelin is, and what happened when it was tested in people

Ipamorelin is a pentapeptide: five amino acids. It was identified in a chemistry programme looking at compounds derived from the growth-hormone-releasing peptides, by removing from the structure the central dipeptide that GHRP-1 carried [1].

What "selective" means, its one distinguishing feature

Peptides in this family release growth hormone, but the earlier ones did something more: GHRP-6 and GHRP-2 also raised ACTH and cortisol. Ipamorelin did not.

In the work that first described it, in conscious swine, none of the secretagogues tested altered FSH, LH, prolactin or TSH; but GHRP-6 and GHRP-2 did raise ACTH and cortisol, while ipamorelin did not move them beyond what GHRH itself did. And that held at doses more than two hundred times higher than the one already producing the growth-hormone effect [1]. That is the literal sense of "the first selective secretagogue".

Potency for releasing growth hormone was measured in three systems: cultured rat pituitary cells, anaesthetised rats and conscious swine. In all three it was comparable to GHRP-6 [1].

What happened in people

Here is the figure that appears on no sales page.

Ipamorelin was taken into a phase 2, randomised, multicentre, placebo-controlled trial in 117 patients undergoing bowel resection, to treat postoperative ileus. The rationale came from a rodent model where the compound had shown a promotility effect in the gut [3].

The primary endpoint was time to tolerating a solid meal. The median was 25.3 hours with ipamorelin and 32.6 with placebo, and the difference did not reach statistical significance (p = 0.15). The authors conclude that it was well tolerated and that there were no significant differences against placebo in the key or the secondary analyses [2].

It is worth reading that precisely, in both directions. That trial did not measure body composition, muscle mass or injury recovery: it measured gut motility after surgery. It does not show that ipamorelin does nothing. What it does show is that the one time it faced the most demanding test there is, it did not pass.

In rats, another paper studied nitrogen balance and urea synthesis in steroid-treated animals [4]. It remains an animal model.

What does not exist

There is no approved human indication for ipamorelin, in the European Union or in the United States. There are no phase 3 trials, no long-term outcomes and no safety data for prolonged use in people.

This page describes published literature. It is not medical information, it does not describe a therapeutic use, and it does not replace any healthcare professional.

What to look at when comparing suppliers

• HPLC purity for the specific batch, with a certificate you can read before buying.
• Identity confirmation, which matters in short peptides: five amino acids leave little room for a superficial analysis to tell one sequence from a similar one.
• Real net content of the vial, not the nominal figure. In lyophilised peptides the gap between declared and weighed is a known source of discrepancy.