Growth & repair
How the body times growth signals — and the peptides that release them.
GH · IGF-1 · GHRH · ghrelin · GHRPs
Overview
Growth hormone (GH) is released from the anterior pituitary in pulses, set by the opposing hypothalamic signals GHRH (stimulatory) and somatostatin (inhibitory). Much of GH's downstream effect is mediated by IGF-1, produced largely in the liver.
A separate axis — ghrelin and the synthetic growth-hormone secretagogues (GHRPs, and small-molecule ghrelin-receptor agonists) — acts on the GHS-R receptor to amplify GH pulses, distinct from the GHRH pathway.
Because the axis is pulsatile and feedback-regulated, the pharmacology of releasing peptides differs fundamentally from administering GH directly — the former works with the body's own rhythm, the latter overrides it.
Key signals
Pulsatile anterior-pituitary hormone; drives growth and metabolism, largely via IGF-1.
Hepatic mediator of GH; promotes tissue growth and provides negative feedback.
Hypothalamic releasing hormone; stimulates GH synthesis and secretion.
Stomach-derived; GHS-R agonist that amplifies GH pulses and signals hunger.
Synthetic GH secretagogues acting at GHS-R, separate from the GHRH receptor.
Reference notes
- GHRH-pathway and ghrelin-pathway secretagogues are synergistic because they act on different receptors.
- Somatostatin is the brake on the axis — any account of GH timing has to include it.
- IGF-1 feedback means sustained secretagogue exposure does not produce unbounded GH; the loop self-limits.
- Distinguish endogenous-releasing approaches from exogenous GH — the safety and regulatory profiles are not the same.
Analogs & therapeutics
Engineered molecules built on this family’s biology — same receptors, re-tuned for stability and duration.