Peptide Hormones: Complete Reference List
Your body runs on chemical signals. Among the most important are peptide hormones --- short chains of amino acids that act as molecular messengers, traveling through the bloodstream to tell distant organs what to do and when to do it.
Your body runs on chemical signals. Among the most important are peptide hormones --- short chains of amino acids that act as molecular messengers, traveling through the bloodstream to tell distant organs what to do and when to do it. From the hypothalamus directing the pituitary gland to the gut signaling satiety after a meal, peptide hormones coordinate nearly every major physiological process.
This reference guide organizes every major peptide hormone by the system that produces it. Use it as a quick-lookup resource when reading research papers, discussing hormone panels with a physician, or simply trying to understand how your body communicates with itself.
Table of Contents
- What Makes a Hormone a "Peptide Hormone"?
- Hypothalamic Peptide Hormones
- Pituitary Peptide Hormones
- Gut (Gastrointestinal) Peptide Hormones
- Pancreatic Peptide Hormones
- Cardiac and Vascular Peptide Hormones
- Reproductive Peptide Hormones
- Bone and Calcium-Regulating Peptide Hormones
- Adipose Tissue Peptide Hormones
- Kidney-Derived Peptide Hormones
- Neuropeptides With Hormonal Functions
- FAQ
- The Bottom Line
- References
What Makes a Hormone a "Peptide Hormone"?
Hormones come in three chemical classes: steroids (like testosterone and cortisol), amino acid derivatives (like thyroid hormones and adrenaline), and peptides/proteins. Peptide hormones are built from chains of amino acids --- anywhere from 3 to over 200. They're synthesized on ribosomes, packaged into secretory vesicles, and released into the bloodstream when triggered.
What sets them apart from steroid hormones is how they work at the target cell. Because peptide hormones are water-soluble, they can't cross the cell membrane. Instead, they bind to receptors on the cell's outer surface, triggering intracellular signaling cascades --- often through second messengers like cyclic AMP (cAMP) or calcium ions. This makes their effects fast but relatively short-lived compared to steroids, which enter the nucleus and alter gene expression directly.
The human body produces well over 100 distinct peptide hormones. What follows is a system-by-system catalog of the most significant ones.
Hypothalamic Peptide Hormones
The hypothalamus is the brain's master regulator of the endocrine system. Sitting just above the pituitary gland, it produces releasing hormones (which stimulate pituitary secretion) and inhibiting hormones (which suppress it). The International Union of Biochemistry and Molecular Biology (IUBMB) uses the suffix "-liberin" for releasing hormones and "-statin" for inhibiting ones.
| Hormone | Also Known As | Size | Primary Function |
|---|---|---|---|
| Thyrotropin-releasing hormone (TRH) | Thyroliberin | 3 amino acids | Stimulates TSH and prolactin release from the anterior pituitary |
| Gonadotropin-releasing hormone (GnRH) | Gonadoliberin, LHRH | 10 amino acids | Triggers release of FSH and LH from the anterior pituitary; master switch for reproductive function |
| Corticotropin-releasing hormone (CRH) | Corticoliberin | 41 amino acids | Activates the HPA stress axis by stimulating ACTH release |
| Growth hormone-releasing hormone (GHRH) | Somatoliberin | 44 amino acids | Stimulates growth hormone secretion from somatotroph cells |
| Somatostatin | Growth hormone-inhibiting hormone (GHIH) | 14 or 28 amino acids | Inhibits GH, TSH, insulin, glucagon, and gastrin; produced in the hypothalamus, gut, and pancreas |
| Oxytocin | --- | 9 amino acids | Produced in hypothalamic nuclei, stored in posterior pituitary; drives uterine contractions, milk ejection, and social bonding |
| Vasopressin (ADH) | Arginine vasopressin (AVP), antidiuretic hormone | 9 amino acids | Produced in hypothalamic nuclei, stored in posterior pituitary; regulates water retention and blood pressure |
| Orexin A and B | Hypocretin 1 and 2 | 33 and 28 amino acids | Regulate wakefulness, appetite, and energy expenditure; loss linked to narcolepsy |
| Melanin-concentrating hormone (MCH) | --- | 19 amino acids | Stimulates appetite and reduces energy expenditure |
| Agouti-related peptide (AgRP) | --- | 132 amino acids | Potent appetite stimulant; antagonizes MC3R and MC4R melanocortin receptors |
| CART peptide | Cocaine- and amphetamine-regulated transcript | 48 or 89 amino acids | Appetite suppression, reward processing, stress response |
| Galanin | --- | 29--30 amino acids | Modulates feeding, pain, sleep, and cognition |
The hypothalamus also produces kisspeptin, a peptide that triggers GnRH release and plays a gatekeeper role in puberty onset. Research into kisspeptin has expanded in recent years as a potential fertility treatment.
Pituitary Peptide Hormones
The pituitary gland --- a pea-sized structure at the base of the brain --- translates hypothalamic signals into hormones that reach organs throughout the body. It has two functional lobes with distinct outputs.
Anterior Pituitary
| Hormone | Size | Primary Function | Clinical Relevance |
|---|---|---|---|
| Growth hormone (GH) | 191 amino acids | Stimulates growth, cell reproduction, and IGF-1 production in the liver | Deficiency treated with recombinant GH; excess causes acromegaly |
| Adrenocorticotropic hormone (ACTH) | 39 amino acids | Stimulates cortisol production from the adrenal cortex | Elevated in Addison's disease; suppressed in Cushing's syndrome from exogenous steroids |
| Prolactin | 199 amino acids | Stimulates milk production; modulates immune function and behavior | Elevated by pituitary tumors (prolactinomas) |
| Thyroid-stimulating hormone (TSH) | Alpha + beta subunit (~211 amino acids total) | Stimulates thyroid hormone production | Primary marker for thyroid function screening |
| Luteinizing hormone (LH) | Alpha + beta subunit | Triggers ovulation in women; stimulates testosterone production in men | Key fertility marker |
| Follicle-stimulating hormone (FSH) | Alpha + beta subunit | Drives follicle development (women) and spermatogenesis (men) | Used in fertility assessment and treatment |
| Alpha-melanocyte-stimulating hormone (alpha-MSH) | 13 amino acids | Regulates skin pigmentation, appetite, and sexual arousal | Basis for PT-141 (bremelanotide) |
| Beta-endorphin | 31 amino acids | Endogenous opioid; pain modulation, stress response, reward | Released during exercise ("runner's high") |
Posterior Pituitary
The posterior pituitary doesn't produce hormones. It stores and releases oxytocin and vasopressin, which are manufactured in the hypothalamus and travel down axons to the posterior lobe for secretion.
Gut (Gastrointestinal) Peptide Hormones
The gastrointestinal tract is the body's largest endocrine organ by cell count. Enteroendocrine cells scattered throughout the gut lining produce dozens of peptide hormones that regulate digestion, appetite, and metabolism. The discovery of GLP-1's metabolic effects led to the blockbuster drugs semaglutide and tirzepatide.
| Hormone | Produced In | Size | Primary Function |
|---|---|---|---|
| Gastrin | G cells (stomach antrum) | 17 or 34 amino acids | Stimulates gastric acid secretion and stomach motility |
| Cholecystokinin (CCK) | I cells (duodenum, jejunum) | 8--58 amino acids (multiple forms) | Stimulates gallbladder contraction, pancreatic enzyme secretion; signals satiety |
| Secretin | S cells (duodenum) | 27 amino acids | Stimulates bicarbonate release from the pancreas to neutralize stomach acid; first hormone ever discovered (1902) |
| Glucagon-like peptide-1 (GLP-1) | L cells (ileum, colon) | 30--31 amino acids | Incretin: stimulates insulin secretion, slows gastric emptying, suppresses appetite |
| Glucagon-like peptide-2 (GLP-2) | L cells (ileum, colon) | 33 amino acids | Promotes intestinal growth and nutrient absorption; basis for teduglutide (Gattex) |
| Glucose-dependent insulinotropic polypeptide (GIP) | K cells (duodenum, jejunum) | 42 amino acids | Incretin: potentiates insulin release; target of tirzepatide |
| Ghrelin | P/D1 cells (stomach fundus) | 28 amino acids | The "hunger hormone"; stimulates appetite and GH release |
| Peptide YY (PYY) | L cells (ileum, colon) | 36 amino acids | Suppresses appetite after eating; slows gut transit |
| Vasoactive intestinal polypeptide (VIP) | Neurons throughout the gut | 28 amino acids | Relaxes smooth muscle, stimulates water secretion, vasodilation |
| Motilin | M cells (duodenum, jejunum) | 22 amino acids | Triggers migrating motor complex; regulates fasting gut motility |
| Neurotensin | N cells (ileum) | 13 amino acids | Modulates gut motility, fat absorption; expressed in some cancers |
| Oxyntomodulin | L cells (ileum, colon) | 37 amino acids | Dual GLP-1/glucagon receptor activity; reduces appetite and increases energy expenditure |
| Substance P | Enteric neurons | 11 amino acids | Pain signaling, inflammation, smooth muscle contraction in the gut |
| Gastrin-releasing peptide (GRP) | Gastric neurons | 27 amino acids | Mammalian equivalent of bombesin; stimulates gastrin release |
For a deeper look at how GLP-1 drugs harness gut hormone biology, see our guide on how GLP-1 medications work.
Pancreatic Peptide Hormones
The islets of Langerhans --- clusters of endocrine cells in the pancreas --- produce the hormones most directly responsible for blood sugar control. These peptides are among the most clinically significant in all of endocrinology.
| Hormone | Cell Type | Size | Primary Function | Clinical Relevance |
|---|---|---|---|---|
| Insulin | Beta cells | 51 amino acids (A chain: 21, B chain: 30) | Lowers blood glucose by promoting cellular uptake; stimulates glycogen, fat, and protein synthesis | Deficiency or resistance causes diabetes; first peptide hormone ever isolated (1921) |
| Glucagon | Alpha cells | 29 amino acids | Raises blood glucose by promoting glycogenolysis and gluconeogenesis in the liver | Used as emergency treatment for severe hypoglycemia; see our glucagon profile |
| Amylin (IAPP) | Beta cells | 37 amino acids | Co-secreted with insulin; slows gastric emptying, suppresses glucagon, promotes satiety | Analog pramlintide (Symlin) approved for diabetes; read more in our amylin profile |
| Somatostatin | Delta cells | 14 amino acids | Inhibits insulin, glucagon, gastrin, and other hormones; acts as a broad endocrine brake | Analogs (octreotide, lanreotide) used for acromegaly and neuroendocrine tumors |
| Pancreatic polypeptide (PP) | F cells (PP cells) | 36 amino acids | Reduces appetite; slows gastric emptying; self-regulates pancreatic exocrine secretion | Levels measured as markers for certain neuroendocrine tumors |
| C-peptide | Beta cells | 31 amino acids | Cleaved from proinsulin during insulin processing; now known to have biological activity | Used clinically to measure endogenous insulin production; emerging evidence for vascular protective effects |
Cardiac and Vascular Peptide Hormones
The heart and blood vessels produce peptide hormones that regulate blood pressure, fluid balance, and cardiovascular remodeling. These hormones are now routine clinical biomarkers.
| Hormone | Source | Size | Primary Function | Clinical Relevance |
|---|---|---|---|---|
| Atrial natriuretic peptide (ANP) | Atrial cardiomyocytes | 28 amino acids | Lowers blood pressure; promotes sodium and water excretion by the kidneys | Released in response to atrial stretch from volume overload |
| Brain natriuretic peptide (BNP) | Ventricular cardiomyocytes | 32 amino acids | Same effects as ANP; marker of ventricular wall stress | NT-proBNP blood test used to diagnose and monitor heart failure |
| C-type natriuretic peptide (CNP) | Vascular endothelium, brain | 22 amino acids | Vasodilation; bone growth regulation | Analog vosoritide (Voxzogo) approved for achondroplasia in children |
| Endothelin-1 | Vascular endothelium | 21 amino acids | Most potent vasoconstrictor known; promotes smooth muscle proliferation | Endothelin receptor antagonists (bosentan, ambrisentan) treat pulmonary arterial hypertension |
| Angiotensin II | Formed in blood from angiotensinogen (liver) | 8 amino acids | Vasoconstriction; stimulates aldosterone release; raises blood pressure | Target of ACE inhibitors and ARBs, the most prescribed cardiovascular drug classes |
| Adrenomedullin | Adrenal medulla, vascular endothelium | 52 amino acids | Vasodilation, natriuresis, angiogenesis | Elevated in heart failure and sepsis; being investigated as a biomarker |
For more on natriuretic peptides as diagnostic tools, see our article on natriuretic peptides as cardiac biomarkers.
Reproductive Peptide Hormones
Beyond the steroid sex hormones (estrogen, progesterone, testosterone), several peptide hormones play direct roles in reproduction, pregnancy, and sexual function.
| Hormone | Source | Size | Primary Function |
|---|---|---|---|
| GnRH | Hypothalamus | 10 amino acids | Master regulator of the reproductive axis; pulsatile release drives LH and FSH |
| LH | Anterior pituitary | Glycoprotein (~30 kDa) | Triggers ovulation; stimulates Leydig cell testosterone production |
| FSH | Anterior pituitary | Glycoprotein (~30 kDa) | Follicle maturation in ovaries; Sertoli cell stimulation for spermatogenesis |
| Oxytocin | Hypothalamus / posterior pituitary | 9 amino acids | Uterine contractions during labor; milk let-down; pair bonding |
| Prolactin | Anterior pituitary | 199 amino acids | Milk production; reproductive immunomodulation |
| Inhibin A and B | Ovarian granulosa / testicular Sertoli cells | Alpha + beta subunits | Selectively suppresses FSH secretion; used as a marker for ovarian reserve |
| Activin | Multiple tissues | Beta subunit homodimer | Stimulates FSH release; opposes inhibin |
| Kisspeptin | Hypothalamic KISS1 neurons | 54 amino acids (processed to shorter forms) | Triggers GnRH release; gatekeeper of puberty onset |
| Human chorionic gonadotropin (hCG) | Placental trophoblasts | Glycoprotein (~37 kDa) | Maintains corpus luteum in early pregnancy; basis of pregnancy tests |
| Relaxin | Corpus luteum, placenta | 2-chain peptide (~6 kDa) | Softens cervix, relaxes pelvic ligaments during pregnancy |
| Anti-Mullerian hormone (AMH) | Granulosa / Sertoli cells | Glycoprotein homodimer | Ovarian reserve marker; male sex differentiation during embryonic development |
Bone and Calcium-Regulating Peptide Hormones
Calcium homeostasis is tightly controlled by a handful of peptide hormones that balance bone building against bone resorption.
| Hormone | Source | Size | Primary Function | Clinical Relevance |
|---|---|---|---|---|
| Parathyroid hormone (PTH) | Parathyroid glands | 84 amino acids | Raises blood calcium by stimulating bone resorption, kidney calcium reabsorption, and vitamin D activation | Excess causes hyperparathyroidism; synthetic PTH fragment (teriparatide) treats osteoporosis |
| Calcitonin | Thyroid C cells (parafollicular) | 32 amino acids | Lowers blood calcium by inhibiting osteoclast activity | Salmon calcitonin used for osteoporosis and Paget's disease; weaker effect than PTH |
| Calcitonin gene-related peptide (CGRP) | Sensory neurons | 37 amino acids | Potent vasodilator; pain signaling in trigeminal system | CGRP-blocking antibodies (erenumab, fremanezumab) approved for migraine prevention |
| PTH-related protein (PTHrP) | Multiple tissues | 141 amino acids | Regulates calcium in fetal development; bone and breast biology | Causes hypercalcemia of malignancy when secreted by tumors |
Adipose Tissue Peptide Hormones
Fat tissue is an active endocrine organ. Adipocyte-derived hormones (adipokines) regulate metabolism, inflammation, and appetite.
| Hormone | Size | Primary Function | Clinical Relevance |
|---|---|---|---|
| Leptin | 167 amino acids | Signals energy stores to the brain; suppresses appetite when fat reserves are adequate | Deficiency causes severe obesity; resistance common in obesity |
| Adiponectin | 244 amino acids | Improves insulin sensitivity; anti-inflammatory; cardioprotective | Low levels associated with type 2 diabetes, metabolic syndrome, and cardiovascular disease |
| Resistin | 108 amino acids | May promote insulin resistance and inflammation | Elevated in obesity; role debated in humans vs. rodents |
| Visfatin (NAMPT) | 491 amino acids | Mimics insulin in some assays; involved in NAD+ biosynthesis | Elevated in visceral fat; possible inflammatory mediator |
| Apelin | 77 amino acids (processed to shorter forms) | Cardiovascular regulation, fluid homeostasis, angiogenesis | Altered in heart failure and pulmonary hypertension |
Kidney-Derived Peptide Hormones
| Hormone | Size | Primary Function | Clinical Relevance |
|---|---|---|---|
| Erythropoietin (EPO) | 165 amino acids | Stimulates red blood cell production in bone marrow | Recombinant EPO treats anemia in chronic kidney disease; abused in endurance sports |
| Renin | 340 amino acids (enzyme/prohormone) | Cleaves angiotensinogen to angiotensin I, initiating the renin-angiotensin-aldosterone system (RAAS) | Direct renin inhibitor (aliskiren) approved for hypertension |
| Uroguanylin | 16 amino acids | Regulates intestinal and renal sodium/water handling | Related to guanylate cyclase-C agonists (linaclotide, plecanatide) used for constipation |
Neuropeptides With Hormonal Functions
Some peptides produced primarily in the nervous system also circulate as hormones or have significant endocrine effects. For a broader look, see our neuropeptides category overview.
| Neuropeptide | Size | Primary Function | Clinical Relevance |
|---|---|---|---|
| Neuropeptide Y (NPY) | 36 amino acids | Potent appetite stimulant; stress response; vasoconstriction | One of the most abundant neuropeptides in the brain |
| Substance P | 11 amino acids | Pain transmission; inflammation; mood regulation | Target of aprepitant (Emend) for chemotherapy-induced nausea |
| CGRP | 37 amino acids | Vasodilation; migraine pathophysiology | Anti-CGRP therapies are first-class migraine preventives |
| Endorphins (alpha, beta, gamma) | 16--31 amino acids | Endogenous opioids; pain modulation; stress resilience | Beta-endorphin is the most studied; released by exercise and acupuncture |
| Enkephalins (met- and leu-) | 5 amino acids each | Endogenous opioid signaling; pain gating in the spinal cord | Short-lived due to rapid enzymatic breakdown |
| Dynorphins | 8--17 amino acids | Kappa opioid receptor agonists; pain modulation, mood | Involved in stress-induced dysphoria; target of kappa antagonist research |
| Cholecystokinin (CCK) | 8--58 amino acids | Both a gut hormone and brain neuropeptide; satiety signaling, anxiety modulation | Found in highest concentrations in the cerebral cortex |
| VIP | 28 amino acids | Neurotransmitter in the gut and brain; circadian rhythm regulation, immune modulation | Investigated for CIRS/mold illness treatment |
FAQ
How many peptide hormones exist in the human body?
Estimates range from 100 to over 300, depending on how you count splice variants and post-translational modifications. The exact number keeps growing as researchers identify new bioactive peptide fragments. The tables above cover the most physiologically and clinically significant ones.
What is the difference between a peptide hormone and a protein hormone?
The distinction is somewhat arbitrary. Traditionally, peptides contain fewer than about 50 amino acids, while proteins contain more. In practice, endocrinologists use "peptide hormone" as a blanket term for both. Insulin (51 amino acids) and growth hormone (191 amino acids) are both commonly called peptide hormones.
Are peptide hormones the same as peptide drugs?
Not exactly. Peptide drugs are synthetic or recombinant versions designed to mimic, block, or modify the action of natural peptide hormones. For example, semaglutide is a modified GLP-1 analog, and tesamorelin is a GHRH analog. See our complete list of FDA-approved peptide drugs for the full catalog.
Why can't peptide hormones be taken as pills?
Most peptide hormones are digested in the stomach before reaching the bloodstream. That's why insulin requires injection. However, oral delivery technology is advancing --- oral semaglutide (Rybelsus) uses an absorption enhancer to survive the GI tract, and more oral peptide formulations are in development.
Which peptide hormone is most clinically important?
Insulin has saved more lives than any other peptide hormone. But measured by current prescription volume, GLP-1 agonists like semaglutide and tirzepatide are the fastest-growing class in pharmaceutical history, projected to generate over $100 billion in annual revenue by the late 2020s.
How are peptide hormone levels tested?
Standard blood tests measure many peptide hormones. Common panels include insulin, C-peptide, GH, IGF-1, ACTH, TSH, LH, FSH, prolactin, PTH, ANP/BNP, and gastrin. Some require specific timing (fasting, morning draw) or stimulation/suppression tests for accurate results.
The Bottom Line
Peptide hormones are the body's primary chemical communication system. They regulate metabolism, growth, reproduction, blood pressure, bone density, appetite, mood, and immune function. Understanding which glands produce which hormones --- and what happens when those signals go wrong --- is the foundation for making sense of endocrine disorders and the peptide therapies designed to treat them.
This list is not exhaustive. New peptide hormones continue to be discovered, and familiar ones keep revealing new functions. The field of peptide research is expanding faster than ever, driven by advances in proteomics, peptidomics, and the clinical success of drugs like semaglutide.
If you're interested in how these natural hormones inspired therapeutic peptides, explore our guides on how peptides work and the complete list of FDA-approved peptide medications.
References
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IUBMB Nomenclature of Peptide Hormones. International Union of Biochemistry and Molecular Biology. https://iubmb.qmul.ac.uk/misc/phorm.html
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Understanding peptide hormones: from precursor proteins to bioactive molecules. Trends in Biochemical Sciences. 2025. https://www.cell.com/trends/biochemical-sciences/fulltext/S0968-0004(25)00063-5
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Peptide Hormones in Medicine: A 100-Year History. Russian Journal of Bioorganic Chemistry. 2022. https://link.springer.com/article/10.1134/S1068162022020157
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Peptide Hormones and Their Receptors. The Medical Biochemistry Page. https://themedicalbiochemistrypage.org/peptide-hormones-and-their-receptors/
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Principles of Endocrinology. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK20/
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Physiology, Parathyroid. StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK482510/
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Peptide Hormone overview. ScienceDirect Topics. https://www.sciencedirect.com/topics/neuroscience/peptide-hormone
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Advance in peptide-based drug development: delivery platforms, therapeutics and vaccines. Signal Transduction and Targeted Therapy. 2024. https://www.nature.com/articles/s41392-024-02107-5