Many organs release hormones besides doing their main job. The kidney, heart and gut all send signals that control blood counts, blood pressure and digestion.
Kidney: erythropoietin
When the kidney senses low oxygen, it releases erythropoietin (EPO), which tells the bone marrow to make more red cells. Failing kidneys make less EPO, so anemia is common in chronic kidney disease.
Kidney: renin and vitamin D
Low blood flow to the kidney triggers the release of renin, which starts the renin-angiotensin-aldosterone system and raises blood pressure. The kidney also makes the active form of vitamin D.
Heart: natriuretic peptides
Stretched heart chambers release ANP and BNP. These make the kidneys lose sodium and water and relax blood vessels, which lowers the load on the heart.
Gut hormones
Gastrin increases stomach acid, while secretin and cholecystokinin release pancreatic juice and bile. GLP-1 boosts insulin after meals, and ghrelin from the stomach signals hunger.
| Hormone | Source | Main effect |
|---|---|---|
| EPO | Kidney | More red blood cells |
| Renin | Kidney | Raises blood pressure through angiotensin and aldosterone |
| BNP | Heart ventricles | Sodium and water loss |
| GLP-1 | Small intestine | More insulin, less appetite |
At the bedside
A high BNP supports heart failure as the cause of breathlessness. Low hemoglobin in a patient with kidney disease often reflects low EPO.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).