Growth Hormone Secretagogues: GHRP-2, GHRP-6, Ipamorelin and Beyond

Growth hormone secretagogues represent one of the most studied classes of research peptides. These compounds act on the ghrelin receptor (GHS-R1a) and the growth hormone releasing hormone (GHRH) receptor to stimulate growth hormone release in research models. In this article, we explore the key secretagogue peptides available for laboratory research and their distinct signalling profiles.

The Two Pathways of GH Release

Growth hormone release in research models is regulated through two principal pathways:

1. The GHRH pathway — Growth hormone releasing hormone acts on the GHRH receptor on somatotropes in the anterior pituitary, stimulating cAMP-mediated GH release. Peptides in this category include Sermorelin, CJC-1295 with DAC, CJC-1295 without DAC, and Tesamorelin.

2. The ghrelin receptor pathway — Ghrelin receptor agonists (GHS) act on the GHS-R1a receptor, providing a complementary GH release signal. Peptides in this category include GHRP-2, GHRP-6, Ipamorelin, and Hexarelin.

GHRP-2 and GHRP-6: First-Generation Secretagogues

GHRP-2 and GHRP-6 are synthetic hexapeptide ghrelin receptor agonists. Both are studied for their potent GH release signalling in in-vitro and preclinical models. GHRP-2 (Pralmorelin) is generally considered more potent than GHRP-6 in research settings, while GHRP-6 is noted for its appetite stimulation signalling alongside GH release.

Ipamorelin: The Selective Secretagogue

Ipamorelin is a pentapeptide ghrelin receptor agonist noted for its selectivity — it stimulates GH release with minimal effect on cortisol, prolactin, or ACTH in research models. This makes it a valuable research tool for studying clean GH release signalling without the confounding hormonal interactions of other GHRPs.

Hexarelin: Dual GH and Cardiac Signalling

Hexarelin is unique among the GHRP class for its additional cardioprotective signalling through the CD36 receptor. This dual activity makes it a compound of interest for researchers studying both GH release and cardiac signalling pathways.

CJC-1295: DAC vs No DAC

CJC-1295 is a GHRH analogue available in two forms:

• CJC-1295 with DAC — The Drug Affinity Complex (DAC) extends the peptide's half-life through albumin binding, producing sustained GH release signalling.
• CJC-1295 without DAC — Also known as Modified GRF (1-29), this variant has a shorter half-life, making it suitable for studying pulsatile GH release patterns that more closely mimic physiological signalling.

Sermorelin and Tesamorelin

Sermorelin is the GHRH 1-29 fragment, the shortest fully active GHRH analogue. Tesamorelin is a stabilised GHRH analogue with a modified N-terminal sequence, studied for both GH release and visceral adipose tissue lipolysis signalling.

Combined Pathway Research

Researchers often study GHRH analogues and ghrelin receptor agonists in combination, as the two pathways act synergistically on GH release. Our existing CJC/Ipamorelin blend provides both pathways in a single vial for combined signalling research.

Purity and Verification

All growth hormone secretagogue peptides from HPLC Peps are independently tested by Janoshik at 99%+ HPLC purity with published Certificates of Analysis. Researchers from Cambridge to Cardiff, Oxford to Aberdeen, and across the UK trust HPLC Peps as their peptide supplier UK for the highest purity GH research compounds, as we are known for our best reviewed peptides.

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For laboratory research use only. Not for human consumption, medical diagnosis, or treatment.