Selective GH secretagogue · ghrelin receptor agonist · research peptide

Ipamorelin

Studied for: pulsatile growth hormone release, IGF-1 elevation (research peptide)

Ipamorelin is a synthetic pentapeptide described in the literature as the first selective growth hormone secretagogue — a ghrelin-receptor agonist that produces a pulsatile GH release without the ACTH, cortisol, or prolactin elevations seen with earlier molecules in the class. It is not FDA-approved, and in October 2024 the FDA's Pharmacy Compounding Advisory Committee voted against including it on the 503A bulks list.

Class
GHS-R1a agonist (ghrelin receptor)
Structure
Pentapeptide (5 AA) · Aib-His-D-2-Nal-D-Phe-Lys-NH₂[1]
Terminal half-life (human)
~2 hours[2]
Tmax
~40 minutes SC[2]
GH return to baseline
~3 hours[2]
Clearance
0.078 L/h/kg[2]
Volume of distribution
0.22 L/kg (steady state)[2]
FDA status
Not approved · PCAC voted against 503A inclusion Oct 2024[3]
Educational reference only. Ipamorelin is not FDA-approved. PCAC voted against its inclusion on the 503A bulks list in October 2024, meaning compounding pharmacies are not authorized to produce it for a listed indication. This page summarizes published research and regulatory status — it does not recommend doses, protocols, or acquisition channels.

Last reviewed April 24, 2026 by the Enhanced Health Editorial Team. See the editorial policy.

What ipamorelin is

Ipamorelin is a synthetic pentapeptide — five amino acids joined in a specific order, with N-terminal aminoisobutyric acid (Aib), histidine, D-2-naphthyl-alanine, D-phenylalanine, and C-terminal lysinamide. It was first described in the scientific literature in 1998 by Raun and colleagues at Novo Nordisk as "the first selective growth hormone secretagogue."[1] Its distinguishing feature versus the earlier growth hormone releasing peptides (GHRP-2, GHRP-6, hexarelin) is that it drives GH release without the ACTH, cortisol, or prolactin elevations seen with those older molecules.

Mechanism

Ipamorelin is an agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a) — the same G-protein-coupled receptor activated by endogenous ghrelin. The signaling chain is:[1][4]

  1. Ipamorelin binds GHS-R1a on somatotroph cells in the anterior pituitary.
  2. The receptor couples through Gαq/11 to activate phospholipase C.
  3. Phospholipase C cleaves PIP₂ into IP₃ and DAG.
  4. IP₃ triggers calcium release from the somatotroph endoplasmic reticulum.
  5. Elevated intracellular calcium drives exocytosis of GH-containing secretory granules.

The result is a discrete, time-limited pulse of GH release — peak at approximately 40 minutes post-administration, returning to baseline within roughly 3 hours.[2]

Selectivity — the key distinguishing feature

The published studies of ipamorelin emphasize a specific pharmacological profile: at doses up to more than 200-fold above the ED₅₀ for GH release, ipamorelin does not significantly elevate plasma ACTH, cortisol, or prolactin. Earlier growth hormone releasing peptides (GHRP-2 and GHRP-6 in particular) produce dose-dependent increases in those hormones. This selectivity is the basis for the description of ipamorelin as the "first selective" GH secretagogue in the title of the original characterization paper.[1]

Pharmacokinetics (human)

  • Terminal half-life. Approximately 2 hours.[2]
  • Tmax. Approximately 40 minutes after subcutaneous administration.[2]
  • Clearance. 0.078 L/h/kg.[2]
  • Volume of distribution at steady state. 0.22 L/kg.[2]
  • Dose-proportionality. PK parameters scale linearly with dose in published human studies.[2]
  • Metabolism and elimination. Peptidase-mediated breakdown; primarily renal excretion of metabolites.

Regulatory status

  • FDA approval. None. Ipamorelin is not approved for any clinical indication.
  • PCAC vote. At its October 2024 meeting, the Pharmacy Compounding Advisory Committee voted against including ipamorelin on the 503A bulks list. That outcome means ipamorelin is not authorized to be compounded by 503A pharmacies for a listed indication absent a new nomination or new evidence.[3]
  • April 15, 2026 503A update. Ipamorelin was not part of the April 15, 2026 Category 2 removal list (which covered BPC-157, TB-500, GHK-Cu injectable, MOTS-c, KPV, Epitalon, DSIP, Dihexa, Ibutamoren, Melanotan II, Semax, and Cathelicidin LL-37).

Storage and handling

  • Lyophilized powder. Store sealed per supplier instructions — typically refrigerated at 2–8 °C or frozen at −20 °C.
  • After reconstitution. Refrigerate at 2–8 °C. Bacteriostatic water (0.9% benzyl alcohol) for multi-draw; sterile water for single-draw.
  • Handling. Swirl — do not shake. Avoid freeze–thaw. Discard cloudy or discolored solutions.

Reconstitution math

Math only — no dose recommendation. The concentration after reconstitution determines how many insulin-syringe units equal a given mcg amount.

Example 1 · 5 mg vial + 2 mL bac water concentration = 5 mg / 2 mL = 2.5 mg/mL = 2500 mcg/mL
1 unit = 0.01 mL = 25 mcg
→ 100 mcg = 4 units
→ 200 mcg = 8 units
→ 300 mcg = 12 units
→ 500 mcg = 20 units
Example 2 · 5 mg vial + 1 mL bac water concentration = 5 mg / 1 mL = 5 mg/mL = 5000 mcg/mL
1 unit = 0.01 mL = 50 mcg
→ 100 mcg = 2 units
→ 200 mcg = 4 units
→ 300 mcg = 6 units
→ 500 mcg = 10 units
Example 3 · 10 mg vial + 2 mL bac water concentration = 10 mg / 2 mL = 5 mg/mL = 5000 mcg/mL
1 unit = 0.01 mL = 50 mcg
→ 100 mcg = 2 units
→ 500 mcg = 10 units
→ 1 mg = 20 units
→ 5 mg = 100 units (full syringe)

Frequently asked questions

What is ipamorelin?

Synthetic pentapeptide, ghrelin-receptor (GHS-R1a) agonist. First described 1998. The first "selective" GH secretagogue — elevates GH but not ACTH/cortisol/prolactin.[1]

How does it work?

GHS-R1a → Gαq/11 → phospholipase C → IP₃ → intracellular calcium release → GH exocytosis from pituitary somatotrophs. Pulsatile release; peaks ~40 min.[1][4]

What's the half-life?

~2 hours (human PK published). Clearance 0.078 L/h/kg, Vd 0.22 L/kg.[2]

Ipamorelin vs CJC-1295?

Different mechanism (ghrelin receptor vs GHRH receptor), different half-life (~2 hours vs ~6–8 days with DAC), often studied together as complementary arms of GH regulation.

How do I reconstitute a 5 mg vial?

Typical: 5 mg + 2 mL bacteriostatic water = 2.5 mg/mL → 1 unit = 25 mcg; 100 mcg = 4 units. Using 1 mL doubles the concentration.

Is it FDA-approved?

No. PCAC voted AGAINST inclusion on the 503A bulks list in October 2024.[3] Not compoundable for a listed indication.

Why no cortisol/ACTH elevation like earlier GHRPs?

Earlier GHRPs (GHRP-2, GHRP-6) produced dose-dependent elevations in ACTH, cortisol, and prolactin. Ipamorelin is structurally engineered for selectivity — its D-2-Nal and D-Phe residues give a GHS-R1a binding profile that drives GH exocytosis without activating the downstream signaling that elevated those hormones in earlier molecules. The selectivity held in trials at doses more than 200-fold above the ED₅₀ for GH release.[1]

Primary references

  1. Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol, 1998;139:552–561 (PubMed 9849822). PubMed 9849822
  2. Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res, 1999;16:1412–1416 (PubMed 10496658). PubMed 10496658 · Springer
  3. U.S. Food and Drug Administration. Pharmacy Compounding Advisory Committee (PCAC) — October 2024 meeting. PCAC voted against ipamorelin for inclusion on the 503A bulks list. fda.gov/PCAC
  4. Ishida J, Saitoh M, Springer J, et al. Growth hormone secretagogues: history, mechanism of action, and clinical development. JCSM Rapid Communications, 2020. Wiley Online Library

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