The Complete Landscape of Growth Hormone Releasing Compounds and Their Receptors
This review maps the full spectrum of GH-releasing substances from GHRP-6 to MK-677, their receptor types, and how the discovery of the natural ligand ghrelin transformed the field.
Quick Facts
What This Study Found
Structurally diverse GH secretagogues (peptides and non-peptides) all converge on the GHS receptor, whose cloning predicted the existence of a natural ligand — later identified as ghrelin — with widespread physiological roles beyond GH release.
Key Numbers
How They Did This
Comprehensive review of GH-releasing substance pharmacology, receptor biology, and physiological significance, covering peptide and non-peptide secretagogues.
Why This Research Matters
This review captures a pivotal moment when synthetic GH secretagogues led to the discovery of a major new hormone (ghrelin), demonstrating how drug development can reveal fundamental biology.
The Bigger Picture
The GH secretagogue story is a remarkable example of reverse pharmacology — synthetic drugs were developed before the natural hormone (ghrelin) was discovered. This revolutionized understanding of appetite, metabolism, and GH regulation.
What This Study Doesn't Tell Us
Review from 1999, just before ghrelin's formal identification. Some receptor characterization was preliminary.
Questions This Raises
- ?What is the natural function of the GHS-R system?
- ?Can receptor subtype-selective drugs target specific tissues?
- ?How does the ghrelin system interact with other metabolic hormones?
Trust & Context
- Key Stat:
- Drugs predicted a hormone Synthetic GH secretagogues led to GHS-R cloning, which predicted ghrelin's existence before its discovery — reverse pharmacology in action
- Evidence Grade:
- Strong evidence from a comprehensive review synthesizing pharmacological, molecular, and physiological data from the entire GH secretagogue field.
- Study Age:
- Published in 1999, just before ghrelin's identification in 1999. This review captures the state of knowledge at this historic transition.
- Original Title:
- Growth hormone releasing substances: types and their receptors.
- Published In:
- Hormone research, 51 Suppl 3, 1-8 (1999)
- Authors:
- Smith, R G(15), Palyha, O C(2), Feighner, S D(6), Tan, C P, McKee, K K, Hreniuk, D L, Yang, L, Morriello, G, Nargund, R, Patchett, A A, Howard, A D
- Database ID:
- RPEP-00563
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
What's the connection between GH peptides and the hunger hormone?
Synthetic GH-releasing peptides were developed first. Scientists discovered they all work through the same receptor. Searching for the body's natural molecule for this receptor led to the discovery of ghrelin, now known as the hunger hormone.
Why are there so many different GH secretagogues?
Researchers developed peptides (GHRP-6, hexarelin, ipamorelin) and non-peptides (MK-677) with different properties. Despite their structural diversity, they all activate the same receptor, with different selectivity and side effect profiles.
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Cite This Study
https://rethinkpeptides.com/research/RPEP-00563APA
Smith, R G; Palyha, O C; Feighner, S D; Tan, C P; McKee, K K; Hreniuk, D L; Yang, L; Morriello, G; Nargund, R; Patchett, A A; Howard, A D. (1999). Growth hormone releasing substances: types and their receptors.. Hormone research, 51 Suppl 3, 1-8.
MLA
Smith, R G, et al. "Growth hormone releasing substances: types and their receptors.." Hormone research, 1999.
RethinkPeptides
RethinkPeptides Research Database. "Growth hormone releasing substances: types and their recepto..." RPEP-00563. Retrieved from https://rethinkpeptides.com/research/smith-1999-growth-hormone-releasing-substances
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkPeptides research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.