Where each hormone is made, whether it's stored, what triggers its release, what it does, and where it acts — built from the GI deck (core) and the metabolism, nutrition, energetics & blood decks.
| Hormone | Formed in | Stored in | Stimulus for release | What it does (effect) | Acts on |
|---|---|---|---|---|---|
| Gastrin | G-cells of the stomach antrum (pyloric glands) | Granules of the G-cell → released into blood | Peptides & amino acids in the stomach, distension, vagus (GRP). Blocked by low pH <3 via somatostatin | Strongly drives gastric acid (HCl) secretion; trophic growth of gastric, duodenal & colonic mucosa | Parietal cells (via ECL-cell histamine) & gastric mucosa |
| Cholecystokinin CCK | I-cells of the duodenum & jejunum | Granules of the I-cell | Fatty acids / monoglycerides, peptides & amino acids (acid weakly) | Contracts gallbladder + relaxes sphincter of Oddi; potent stimulus for pancreatic enzymes; slows gastric emptying | Gallbladder, pancreas (acinar cells), stomach |
| Secretin "nature's antacid" | S-cells of the duodenum & jejunum | Granules of the S-cell | Acid in the duodenum (pH <4.5); fatty acids | Stimulates pancreatic & biliary bicarbonate; inhibits gastric acid & gastrin; stimulates pepsinogen | Pancreatic ducts, bile ducts / liver, stomach |
| GIP glucose-dependent insulinotropic peptide | K-cells of the duodenum & proximal jejunum | Granules of the K-cell | All foodstuffs (fat must be digested first); oral glucose, not IV | Stimulates insulin release (an incretin); inhibits gastric acid secretion | Pancreatic β-cells; stomach |
| Motilin | M-cells of the duodenum & proximal jejunum | Granules of the M-cell | Fasting (cyclic ~90 min), neural control; duodenal acid & fat | Triggers migrating motor complexes — the between-meal "housekeeping" waves | Smooth muscle of stomach & small intestine |
| Messenger | Formed in | Stored in | Stimulus for release | What it does (effect) | Acts on |
|---|---|---|---|---|---|
| Somatostatin | D-cells of gastric & duodenal mucosa and the pancreas | Granules of the D-cell (acts locally) | Acid & foodstuffs; inhibited by vagal ACh | The universal "off switch" — inhibits release of all gut hormones and directly inhibits parietal-cell acid | Neighboring G-cells & parietal cells |
| Histamine | ECL cells of the stomach | Granules of the ECL cell (acts locally) | Gastrin & acetylcholine | Stimulates gastric acid secretion (via H₂ receptors — the target of H₂ blockers) | Parietal cells |
| Hormone | Formed in | Stored in | Stimulus for release | What it does (effect) | Acts on |
|---|---|---|---|---|---|
| Insulin | β-cells of the pancreatic islets | Granules of the β-cell | Rising blood glucose (also amino acids & incretins like GIP) | Lowers blood glucose — drives cell uptake (GLUT-4) and storage of glycogen, fat & protein | Liver, muscle, fat (most cells) |
| Glucagon | α-cells of the pancreatic islets | Granules of the α-cell | Low blood glucose (fasting) | Raises blood glucose — glycogen breakdown & gluconeogenesis; frees fat | Liver (mainly) |
| Epinephrine | Adrenal medulla | Chromaffin granules | Sympathetic activation (stress, exercise, low glucose) | Mobilizes fuel — raises blood glucose (glycogenolysis) and releases free fatty acids | Liver, muscle, fat (widespread) |
| Cortisol glucocorticoid | Adrenal cortex | Not stored — made on demand from cholesterol | ACTH (stress, fasting) | Raises blood glucose; breaks down protein (catabolic) | Liver, muscle (widespread) |
| Growth hormone | Anterior pituitary | Granules of the pituitary cell | GHRH, fasting / low glucose, deep sleep, exercise | Increases protein synthesis (anabolic), promotes growth, spares glucose by using fat | Most tissues (partly via liver IGF-1) |
| Thyroxine thyroid hormone, T₄/T₃ | Thyroid follicular cells | Stored extracellularly in follicle colloid (thyroglobulin) — a large reserve | TSH from the pituitary; cold exposure | Raises basal metabolic rate & heat production | Nearly all cells |
| Leptin | Fat cells (adipocytes) | Not stored — released in proportion to fat mass | Increased body-fat stores (fed state) | Satiety signal — reduces appetite and raises energy expenditure | Hypothalamus (feeding centers) |
| Ghrelin | Stomach (mainly) | Granules of the stomach cell | Empty stomach, before meals | The hunger hormone — stimulates eating | Hypothalamus (feeding centers) |
| Erythropoietin EPO | Kidney (EPO-producing fibroblasts; ~10% liver) | Not stored — made on demand during hypoxia | Low tissue oxygen (hypoxia) | Stimulates red-blood-cell production | Erythroid precursors in red marrow |