Educational information only — not medical advice or guidance. Content is sourced from the public internet, may contain inaccuracies, and is not written or reviewed by medical professionals. See our full disclaimer.

PRPeptide Research Hub
← Back to database

Growth Hormone Secretagogue

Ipamorelin

Also known as: NNC 26-0161

A pentapeptide growth hormone secretagogue studied for its selective stimulation of growth hormone release without the cortisol/ACTH elevation seen with earlier secretagogues.

Educational content, not advice. Compiled from information publicly available on the internet; it may contain inaccuracies and was not written or reviewed by medical professionals. Use it as a starting point for your own research, verify against primary sources, and see our full disclaimer.

Overview

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) originally characterized by Novo Nordisk researchers as a growth hormone secretagogue receptor (GHS-R1a) agonist. The defining finding of the foundational 1998 study is selectivity: unlike earlier growth-hormone-releasing peptides (e.g., GHRP-6, GHRP-2), ipamorelin stimulated growth hormone release without significantly elevating ACTH, cortisol, prolactin, or other pituitary hormones in the animal models tested.

Proposed Mechanism of Action

Ipamorelin binds the GHS-R1a receptor, expressed in the pituitary and hypothalamus, triggering intracellular signaling that stimulates growth hormone release — mechanistically similar to endogenous ghrelin signaling, but with reported selectivity for the GH axis over the HPA (cortisol) axis in the cited animal data.

Research Context

The cited study reports in vitro potency data (rat pituitary cell culture), an anesthetized rat model, and a conscious swine model — it does not include human clinical trial data. "ED50" values reported here describe the dose producing a half-maximal response in that specific experimental model; they are pharmacological benchmarks, not a dosing protocol designed for repeated administration.

Limitations of the Current Evidence

  • The foundational characterization data is nearly three decades old and centers on animal models; contemporary human clinical trial data for ipamorelin specifically (as opposed to related GH secretagogues) is limited in the peer-reviewed literature.
  • ED50 figures describe a single-dose pharmacological response, not a validated multi-dose research protocol.

Research-Setting Dosing (as reported in literature)

RouteRange (as reported)FrequencyNotes
Subcutaneous / IV (anesthetized rat model)80–80 nmol/kg (ED50)—ED50 = 80 ± 42 nmol/kg in pentobarbital-anesthetized rats — this is the dose producing half-maximal GH response in the model, not a repeat-dosing protocol.
Conscious swine model2.3–2.3 nmol/kg (ED50)—ED50 = 2.3 ± 0.03 nmol/kg in conscious pigs. No elevation in ACTH or cortisol was observed even at doses more than 200x the ED50.

Figures above are extracted directly from the cited preclinical/research literature. They describe what researchers administered to study subjects (frequently animal models) — they are not human dosing recommendations and are not medical advice.

Cited Studies

  • Ipamorelin, the first selective growth hormone secretagogue

    Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH · European Journal of Endocrinology · 1998

    Animal study (rat, swine, in vitro)View source →

Last updated August 1, 2026