Growth Hormone-Releasing Peptides: A Comprehensive Review of How They Work | Research

The takeaway

GHRPs stimulate growth hormone release through a receptor distinct from GHRH, working at both the pituitary and hypothalamic levels with consistent effects across species and administration routes.

Distinct receptor from GHRH
GHRPs work through a separate receptor at both the pituitary and hypothalamic level, complementing rather than duplicating GHRH signaling

What the researchers found

GHRPs stimulate growth hormone release through a receptor distinct from GHRH, acting at both the pituitary and hypothalamic level, with consistent effects demonstrated across species and administration routes.

Why it matters

Understanding GHRPs' distinct mechanism opened the door to combination therapies with GHRH and led to the discovery of the ghrelin receptor, transforming growth hormone research.

How the study worked

Comprehensive literature review covering in vivo and in vitro studies of GHRPs in animals and humans, examining mechanisms, dose-response relationships, and clinical applications.

What this study cannot tell us

As a review article from 1996, it predates the discovery of ghrelin and the full characterization of the GHS receptor. Some conclusions may have been refined by subsequent research.

How to read the evidence

Moderate evidence from a comprehensive review covering animal and human studies. Provides a solid foundation but predates key discoveries about the ghrelin/GHS receptor.

When this study was published

Published in 1996, this review predates the discovery of ghrelin (1999). Many of its conclusions about GHRP mechanisms were subsequently confirmed and expanded.

The bigger picture

This review captured the state of GHRP science at a pivotal moment — just before the discovery that the GHRP receptor's natural ligand is ghrelin, which would revolutionize understanding of growth hormone regulation and appetite.

Questions still open

What is the endogenous ligand for the GHRP receptor?
Could GHRPs be developed as practical clinical agents for growth hormone deficiency?

Common questions

How are GHRPs different from GHRH?

GHRPs and GHRH both stimulate growth hormone release, but they work through completely different receptors and signaling pathways. GHRPs act on what's now known as the ghrelin receptor, while GHRH acts on its own dedicated receptor. This means they can be combined for a synergistic effect.

Can GHRPs be taken orally?

Some GHRPs show oral activity, though it's generally less potent than injection. This review discusses various administration routes including oral, intranasal, and injectable, noting that GHRPs are effective across multiple delivery methods.

Read the original research

Growth hormone-releasing peptides: clinical and basic aspects.

Hormone research, 46(4-5), 155-9

View on PubMed ↗

Citation

Argente, J; García-Segura, L M; Pozo, J; Chowen, J A. (1996). Growth hormone-releasing peptides: clinical and basic aspects.. Hormone research, 46(4-5), 155-9.