Ipamorelin vs HGH 191aa: GH-Axis Research Compared

These two are frequently grouped because both sit in the growth-hormone axis — but they work at opposite ends of it. One tells the pituitary to release; the other is the hormone itself.

Two points on the same axis

Property	Ipamorelin	HGH 191aa
Role	GHS-R secretagogue (pentapeptide)	Full 191aa recombinant somatropin
Molecular weight	≈ 712 g/mol	≈ 22,125 g/mol
Vial	5 mg lyophilized	10 IU lyophilized
Unit system	µg	IU

Ipamorelin is a highly selective ghrelin-mimetic pentapeptide that stimulates the growth-hormone secretagogue receptor. HGH 191aa is the complete hormone — all 191 amino acids, verified by SDS-PAGE and HPLC — used directly as the reference standard in receptor signaling and cell proliferation studies.

The unit systems don’t mix

This is where protocols go sideways. HGH is bioassayed in international units; ipamorelin is a synthetic peptide weighed in milligrams. A 5 mg ipamorelin vial and a 10 IU HGH vial are different scales entirely.

The reconstitution calculator has presets for both and switches the math automatically: mg-based vials work in µg, while the HGH preset switches to IU arithmetic so concentrations and draws stay consistent.

Choosing for research

A secretagogue-based protocol studies the release pathway — receptor selectivity, pulse dynamics, feedback. A full-hormone protocol studies the downstream effector. Some protocols combine both; when they do, the two unit systems need careful bookkeeping, which is exactly what the calculator is for.

Practical notes

Both are lyophilized at −20 °C and reconstituted with bacteriostatic water. Full specs: Ipamorelin and HGH 191aa.

For laboratory research use only. Not medical advice.