Peptigrade

Growth Hormone Axis

Ipamorelin

Selective growth hormone secretagogue·Also known as: NNC 26-0161

FDARegulatory status

Not approved for human use

WADARegulatory status

Prohibited at all times (S2 — peptide hormones / GH releasing factors)

Regulatory note ·Originally developed by Novo Nordisk; clinical development discontinued. Sold as a research chemical and through some 503A compounding pharmacies. WADA prohibition is enforced and tested for in competition.

§ The quick take

TL;DR · Editor’s summary

Ipamorelin is one of the cleanest growth hormone secretagogues — it releases GH with high selectivity, avoiding the cortisol and prolactin elevation seen with older compounds like GHRP-6. The acute GH-releasing effect is well-established.

What's much less clear is whether this translates to meaningful clinical outcomes (body composition, sleep, recovery). The honest read: B-grade for the proximal pharmacology, C-grade for downstream clinical claims.

§ Grade matrix

The grade
per outcome.

One peptide can earn very different grades for different uses. Here is every outcome we’ve graded for Ipamorelin, sorted by strength of evidence.

B

GH secretion (acute)

Promising

Multiple human studies confirm dose-dependent GH release with high selectivity (no significant cortisol or prolactin elevation).

24 studiesUpdated Mar 22, 2026
C

Body composition (muscle/fat)

Mixed

Mechanistic plausibility via increased GH/IGF-1 axis activity. Limited direct outcome data in humans.

11 studiesUpdated Feb 18, 2026
C

Sleep quality

Mixed

Indirect evidence via GH and slow-wave sleep relationship. No controlled trials of ipamorelin specifically for sleep.

7 studiesUpdated Jan 30, 2026
D

Bone density

Weak

Mechanistic only. No published human bone density outcome trials with ipamorelin.

4 studiesUpdated Jan 12, 2026

§ Why this grade

Sub-scores for this outcome.

GH secretion

Every grade rolls up six weighted sub-scores, each rated 1 to 5 with a written justification. Here is how the top-outcome grade was constructed.

Mechanism understood

5 / 5

GHS-R1a pharmacology fully characterized.

Human studies (count + quality)

3 / 5

Multiple human PK/PD studies. Phase 1/2 GH deficiency. No Phase 3.

Effect vs placebo

4 / 5

Robust dose-dependent GH spike vs placebo across studies.

Long-term safety data

2 / 5

Limited human data beyond a few months.

Side effect profile

4 / 5

Clean profile vs older GHS — minimal cortisol/prolactin.

Regulatory status

1 / 5

Not approved. WADA-prohibited.

§ What the science says

How Ipamorelin
works.

The scientific explanation of the molecule and its proposed mechanism, with a plain-English translation — written at an 8th-grade reading level — in the teal callouts below each section. Every claim is linked to a primary source below.

What it is

Ipamorelin is a synthetic 5-amino-acid peptide developed in the late 1990s as a selective growth hormone secretagogue. It binds the ghrelin/GHS receptor in the pituitary to trigger growth hormone release. Unlike older GHS compounds, it does not significantly stimulate cortisol, prolactin, or aldosterone. Novo Nordisk advanced it to early clinical trials but discontinued development.

In plain English

Ipamorelin is a lab-made chain of 5 amino acids (the building blocks of proteins). It was designed in the late 1990s to make the pituitary gland (a small gland in the brain) release growth hormone. It does this by attaching to a receiver called the ghrelin receptor — the same receiver that your "hunger hormone" uses. Unlike older drugs of this type, ipamorelin does NOT also raise cortisol (the stress hormone), prolactin, or aldosterone. A Danish drug company (Novo Nordisk) tested it in early human trials and then dropped the project.

How it works

  1. 01

    Ipamorelin selectively binds and activates the GHS-R1a receptor (the ghrelin receptor) in the anterior pituitary.

    In plain English

    Ipamorelin latches onto a specific receiver (called GHS-R1a) on cells in the pituitary gland in your brain. That same receiver is where your natural "hunger hormone" (ghrelin) works.

  2. 02

    Receptor activation triggers a dose-dependent release of stored growth hormone from somatotroph cells, producing a transient GH spike.

    In plain English

    When the receiver is switched on, pituitary cells release the growth hormone they had stored up. The more ipamorelin, the bigger the growth-hormone spike. The spike doesn't last long — it's a short burst.

  3. 03

    Unlike older secretagogues (GHRP-2, GHRP-6, hexarelin), it shows minimal cross-activation of receptors that release ACTH, prolactin, or aldosterone — hence its 'clean' reputation.

    In plain English

    Older drugs in this family (like GHRP-2, GHRP-6, and hexarelin) also accidentally switch on receivers that raise stress hormones and other hormones. Ipamorelin does not — that's why it's called a "clean" version.

  4. 04

    Released GH stimulates hepatic IGF-1 production, which mediates many of the downstream anabolic and metabolic effects attributed to GH therapy.

    In plain English

    Growth hormone then travels to the liver, which releases another hormone called IGF-1. IGF-1 is what actually drives most of the effects people associate with growth hormone — muscle growth, fat use, and tissue repair.

§ Investigated uses

What it’s
been studied for.

Investigated does not mean proven. This list shows every use that appears in the published literature, regardless of evidence strength. See the grade matrix above for which ones have actually held up.

  • Diagnostic GH stimulation testing

    Investigated as a stim test alternative

  • Adult growth hormone deficiency

    Phase 1/2 conducted, development discontinued — Grade B for proximal effect

  • Body composition / lean mass support

    Anecdotal clinical use, limited controlled data — Grade C

  • Sleep architecture (slow-wave sleep)

    Indirect mechanistic case — Grade C

  • Bone density

    Speculative — Grade D

§ The honest gaps

What we don’t
know yet.

Every peptide page on this site is required to include this section. Absence of evidence is information. If we don’t flag the gaps, we’re lying by omission.

  • !

    Whether sustained GH pulses from ipamorelin produce clinically meaningful outcomes equivalent to direct GH or somatropin therapy is largely untested.

  • !

    Long-term safety of repeated GH stimulation in adults with normal pituitary function is poorly characterized.

  • !

    Theoretical concerns about insulin resistance, fluid retention, and tumor growth from sustained IGF-1 elevation have not been adequately studied at typical clinical doses.

  • !

    Optimal dosing protocol (frequency, timing relative to sleep, cycling) lacks comparative trial data.

  • !

    Whether ipamorelin offers meaningful advantages over CJC-1295 / sermorelin or full somatropin is not established by head-to-head trials.

§ On YouTube

What experts and
influencers say.

We index YouTube content discussing Ipamorelinand tag every speaker by credential and trust level. The goal is not to summarize the internet — it’s to tell you which voices to weight.

  • Growth Hormone Peptides Explained: Ipamorelin, CJC-1295, Sermorelin

    Dr. Kyle Gillett·MD, Family Medicine

    Compares the GH-releasing peptides and notes that direct outcome data is limited.

    Verified credentials

§ Citations

Every claim,
linked to source.

All 3 sources informing this page, with DOI or PubMed identifiers. Click through to the primary literature.

  1. [01]

    Ipamorelin, the first selective growth hormone secretagogue

    Raun K, Hansen BS, Johansen NL, et al. · Eur J Endocrinol · 1998

    AnimalPMID 9576629
  2. [02]

    Effects of ipamorelin on the GH/IGF-I axis in healthy male volunteers

    Gobburu JV, Agersø H, Jusko WJ, Ynddal L · Pharm Res · 1999

    RCTPMID 11231057
  3. [03]

    Ghrelin receptor agonists: a review

    Howick K, Griffin BT, Cryan JF, Schellekens H · Int J Mol Sci · 2017

    Systematic reviewPMID 27662485

§ Adjacent peptides

Worth reading
alongside this.

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TB-500

Often co-administered for athletic recovery, despite both being WADA-prohibited and limited combined evidence.

Read its grades

Where to research further

Looking for Ipamorelin
for laboratory research?

Peptigrade does not sell peptides. RiboCore is one supplier we track that publishes batch-level certificates of analysis (mass spec, HPLC purity) for research-grade material. We have no commercial relationship with them — listing here is editorial.

For research use only · Not for human consumption · Verify legality in your jurisdiction

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