Ipamorelin - Growth Hormone

Overview

What Is Ipamorelin?

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that acts as a selective agonist of the growth hormone secretagogue receptor (GHS-R1a), the receptor for the gut hormone ghrelin. Binding at GHS-R1a on pituitary somatotrophs triggers a pulse of growth hormone release that is independent of, and additive to, the body's GHRH-driven pulses. The pulse resembles physiological GH release in shape and duration, peaking within 5 to 15 minutes and clearing within roughly two hours.

Ipamorelin's defining property relative to older GHRPs (GHRP-2, GHRP-6, hexarelin) is selectivity. In the foundational 1998 Raun et al. swine study, it released GH with potency similar to GHRP-6 but did not raise ACTH, cortisol, prolactin, FSH, LH, or TSH even at 200 times the GH ED50. GHRP-6 produces meaningful cortisol and prolactin elevation, GHRP-2 a smaller cortisol rise, and hexarelin raises both while desensitising quickly. Appetite stimulation is the one ghrelin-receptor effect that survives the selectivity filter, because it is mediated by the same GHS-R1a that drives GH release.

Because the size of a GHRP-triggered pulse is gated by endogenous GHRH tone, ipamorelin is most often studied alongside a GHRH analogue such as CJC-1295 (the Bowers synergy effect), where GHRH raises pulse amplitude and the GHRP triggers the pulse. Ipamorelin was developed by Novo Nordisk and reached Phase 2 for post-operative ileus before development was discontinued.

Published Safety Data

What the published studies measured.

What the studies show

Measured in clinical trials

No ACTH, cortisol, prolactin, FSH, LH, or TSH elevation up to 200x the GH ED50 (Raun et al. 1998, pigs) - the defining selectivity finding
Injection site reactions (mild redness, transient itch): 15-25% in clinical reports - mild, resolves within hours
Mild water retention: 10-20% - usually transient, resolves by week 3-4
Peripheral tingling / paresthesia (hands or feet): 5-15% - mild, fluid-pressure mediated, resolves within 2-4 weeks; lower frequency than CJC+Ipa because pulse amplitude is smaller without a GHRH analog
Increased hunger / appetite bump: 10-20% - direct GHS-R1a effect, sharper than with the CJC+Ipa blend because ipamorelin's signal isn't dampened by GHRH co-administration timing
Mild fatigue or drowsiness post-injection: 5-10% - typically only after the pre-bed shot, generally desired
Headache: low single digits - mild
No significant insulin resistance or fasting glucose disturbance at standard doses; mild glucose creep possible at top of advanced band or extended cycles beyond 12 weeks

The Research

Peer-reviewed studies and clinical guidelines - tap any to read the source.

PubMedRaun K, Hansen BS, Johansen NL et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998, 139(5):552-561, PMID 9849822

:552-561, PMID 9849822](https://academic.oup.com/ejendo/article-abstract/139/5/552/6748390) - the defining selectivity paper, ipamorelin releases GH at potency similar to GHRP-6 without ACTH, cortisol, prolactin, FSH, LH, or TSH elevation even at 200x ED50

Read study ↗PubMedBowers CY, Reynolds GA, Durham D et al. GHRH and GHRP synergy on GH release, J Clin Endocrinol Metab 1990, 70(4):975-982

:975-982](https://pubmed.ncbi.nlm.nih.gov/2156870/) - original synergy demonstration showing co-administration produces GH response exceeding the sum of either alone, the foundational rationale for pairing ipamorelin with a GHRH analog

Read study ↗PubMedSinha DK, Balasubramanian A, Tatem AJ et al. Beyond the androgen receptor: the role of growth hormone secretagogues, Transl Androl Urol 2020, 9(Suppl 2):S149-S159

:S149-S159](https://tau.amegroups.com/article/view/35100/html) - review of GHS class including ipamorelin selectivity and clinical positioning

Read study ↗PubMedSackmann-Sala L et al. A mechanistic view of growth hormone signaling pathways, Mol Cell Endocrinol

GHRH/GHRP receptor pathway separation framework, mechanistic basis for combining vs running solo

Read study ↗Clinical guidelinesIpamorelin Research Guide 2026, Your Peptide Brand

synthesis of selectivity data, dosing, comparison to other GHRPs

Read study ↗Clinical guidelinesIpamorelin vs CJC-1295 comparison, Tucson Wellness MD

when to choose standalone Ipa vs the paired blend

Read study ↗

+ 4 more studies & references

Ipamorelin overview and dosing, Anderson Longevity Clinic physician-supervised protocol, fasted-window rationale
Peter Attia AMA #83, peterattiamd.com - Peptides evaluation risk-reward framing on GHRPs and the gap between marketing and human-data
Wittmer Rejuvenation Clinic - Ipamorelin protocol guide 2025 clinical anti-aging framing, sleep + recovery outcomes
Beverly Hills Rejuvenation Center - Ipamorelin profile clinic-protocol dosing

Reconstitution & Storage

Storage: refrigerated, ~30 days after reconstitution. Unreconstituted vials stable at room temp short-term, refrigerate for long-term storage. Do not freeze reconstituted vials.