An introduction to peptide hormones — what they are, how they signal, and their roles in metabolism, growth, reproduction, and stress response.
Filed under basics, written for beginner, patient-consumer, researcher, evidence level A.
Not medically reviewed. Last updated 2026-04-28. Nothing here is medical advice.
Peptide hormones are signaling molecules composed of amino acid chains that regulate nearly every physiological process. Unlike steroid hormones, peptide hormones are water-soluble and typically act on cell-surface receptors.
The hypothalamus produces releasing and inhibiting hormones that control the pituitary gland:
Peptide hormones bind to membrane receptors and trigger intracellular signaling cascades. Unlike steroid hormones that enter cells directly, peptide hormones rely on second messenger systems (cAMP, IP3, calcium) to exert their effects.
Many approved drugs are synthetic analogs of endogenous peptide hormones. Understanding peptide hormone physiology is essential for evaluating therapeutic claims.
This article is for educational purposes and does not provide medical advice.
More guides: All guides, Safety centre, Peptide library.