Peptide Hormone Examples: A Literature-Cited List

Peptide hormones are chemical messengers made of amino acids strung together by peptide bonds. They are produced by endocrine glands and by scattered hormone-secreting cells in the gut, pancreas, placenta and brain, travel in the bloodstream, and bind receptors on the outside of target cells. Because they are water soluble, they do not cross the cell membrane the way lipid-based hormones do. The sections below list named examples from the published literature, each with the tissue that makes it, a chain length class and the function described in the cited source.

This page is a list and comparison page. For the underlying definition, receptor mechanism and signalling background, see the physiology explainer on peptide hormones.

This page is for educational purposes only and is not medical advice; consult a licensed physician about any symptom, laboratory result or treatment question.

Peptide Versus Polypeptide: What the Terms Mean

The two words describe the same chemistry at different lengths. A peptide is a short chain of amino acids. A polypeptide is a longer chain, long enough that it folds into a stable three-dimensional shape and is often also called a protein hormone. The cut-off is conventional rather than biological: many texts place the boundary near 50 amino acid residues, and nothing about the chemistry changes at that number.

Practical groupings used in endocrinology teaching look like this:

• Short peptides, roughly fewer than 20 residues. Oxytocin and vasopressin each have 9 residues; angiotensin II has 8; one form of somatostatin has 14.
• Mid-length peptides, roughly 20 to 50 residues. Ghrelin has 28 residues, glucagon 29, glucagon-like peptide-2 has 33, and amylin 37.
• Polypeptide or protein hormones, above roughly 50 residues. Insulin totals 51 residues across two disulphide-linked chains, growth hormone has 191, and prolactin has 199.

Residue counts quoted here are standard biochemical descriptions of the mature hormones rather than results attributed to any single trial. Glycoprotein hormones such as human chorionic gonadotropin sit at the far end of the size range because they consist of two polypeptide subunits carrying attached sugar chains.

Table: Major Peptide and Polypeptide Hormones

Other peptide and polypeptide hormones exist, including parathyroid hormone, calcitonin, the natriuretic peptides and leptin. They are omitted from the table above because the citation set supporting this page does not cover them, and nothing here should be read as a complete inventory of human peptide hormones.

Grouped by Source Tissue

Hypothalamus and Pituitary

The hypothalamus produces short releasing and inhibiting peptides that reach the anterior pituitary through a local portal circulation, while oxytocin and vasopressin are made in hypothalamic neurons and released from the posterior pituitary. A 2021 handbook chapter on hypothalamic hormone-producing tumours reported that autonomous production of these releasing peptides can drive downstream pituitary hormone excess (PMID 34238480). The posterior pituitary peptides are small: the 2021 diabetes insipidus review reported that absent or ineffective vasopressin signalling leads to polyuria and polydipsia (PMID 33786230).

Pancreatic Islets

Islet peptides illustrate the peptide to polypeptide range inside one organ. Beta cells release insulin, a two-chain polypeptide, and amylin; alpha cells release glucagon. Researchers writing a 2026 historical and physiological review of amylin traced the peptide from its discovery in islet amyloid to its characterisation as a beta cell co-secreted hormone (PMID 41708975), while a 2025 endocrinology review described its effects on gastric emptying, glucagon secretion and satiation signalling (PMID 40360789). The 2023 glucagon centenary review reported glucagon's role in raising hepatic glucose production and summarised a hundred years of work on the proglucagon system (PMID 37367959).

Gastrointestinal Tract

The gut is the largest endocrine organ by cell number. Intestinal L cells cut the proglucagon precursor into different products than alpha cells do, yielding GLP-1 and GLP-2; a 2006 review reported that GLP-2 acts as an intestinotrophic regulator of mucosal growth and absorption (PMID 16602931). In the stomach, a biochemistry review described ghrelin as an octanoylated 28-residue peptide that stimulates growth hormone release and appetite (PMID 31613472). Gastrin and VIP appear in the clinical literature chiefly through the syndromes produced when neuroendocrine tumours secrete them in excess (PMID 37568540).

Placenta

The placenta functions as a temporary endocrine organ. A 2016 overview reported that it secretes protein and peptide hormones including human chorionic gonadotropin and placental lactogen, alongside steroid hormones, to sustain pregnancy and adapt maternal metabolism (PMID 26615903). A 2023 neuroscience review described the broader hormonal transition of the peripartum period and its links to maternal brain and behavioural change (PMID 37612425).

Peptides Made in the Bloodstream

Not every peptide hormone is packaged in a secretory granule. Angiotensin II is cleaved out of a circulating precursor protein by enzymes, and a 2017 review described the resulting renin-angiotensin-aldosterone system as a ubiquitous regulator of blood pressure and fluid balance that is also implicated in a range of pathologies (PMID 28772209).

Hormone Excess and Deficiency States: What Studies Report

Much of what is known about individual peptide hormones comes from reports of what happens when levels are too high or too low. A 2023 review of neuroendocrine neoplasms reported that functional tumours produce syndromes matching their secreted peptide, with insulin-secreting lesions causing hypoglycaemia, gastrin-secreting lesions causing acid hypersecretion and ulcer disease, and VIP-secreting lesions causing watery diarrhoea with electrolyte disturbance (PMID 37568540). On the deficiency side, a 2021 review reported that diabetes insipidus arises either from inadequate vasopressin release or from renal unresponsiveness to it, and described the diagnostic separation of those two mechanisms (PMID 33786230). A 2021 chapter reported that hypothalamic tumours producing releasing hormones generate pituitary-driven excess syndromes rather than acting directly on peripheral tissue (PMID 34238480). These are descriptions of disease states in the published literature, not guidance about any individual case, and any personal question about hormone testing or symptoms belongs with a licensed physician.

Reading the Literature on Peptide Hormones

Several practical habits help when comparing sources on this topic. First, check whether the study being quoted measured the hormone in humans, in isolated cells or in animals, since the species and preparation shape what the numbers mean. Second, note whether a paper discusses the natural hormone or an engineered analogue, because reviews of amylin science covered both the native 37-residue peptide and the longer research history behind analogue development (PMID 41708975). Third, remember that a single precursor protein can yield several hormones, which is why glucagon and the glucagon-like peptides are frequently reviewed together (PMID 37367959). Reviews summarise many primary studies at once, so they are useful maps of a field, but they report other researchers' measurements rather than new ones.

References

• The transition to motherhood: linking hormones, brain and behaviour (Nature Reviews Neuroscience, 2023)
• A Comprehensive Review on Neuroendocrine Neoplasms: Presentation, Pathophysiology and Management (Journal of Clinical Medicine, 2023)
• The endocrine function of human placenta: an overview (Reproductive BioMedicine Online, 2016)
• Diabetes Insipidus: Pathogenesis, Diagnosis, and Clinical Management (Cureus, 2021)
• 100 years of glucagon and 100 more (Diabetologia, 2023)
• The story of amylin: from physiology to therapy (Nature Metabolism, 2026)
• Hypothalamic hormone-producing tumors (Handbook of Clinical Neurology, 2021)
• Amylin: emergent therapeutic opportunities in overweight, obesity and diabetes mellitus (Nature Reviews Endocrinology, 2025)
• Glucagon-like Peptide-2 (Annual Review of Nutrition, 2006)
• Renin-angiotensin-aldosterone (RAAS): The ubiquitous system for homeostasis and pathologies (Biomedicine & Pharmacotherapy, 2017)
• Biochemistry, Ghrelin (StatPearls, 2023)