The kidney decides how much water and salt leave the body, but hormones give the orders. The kidney also makes hormones of its own for blood pressure, red blood cells and bone.
ADH
Antidiuretic hormone from the posterior pituitary opens water channels in the collecting duct, so the body keeps water. It rises when blood becomes too concentrated or blood volume falls.
Renin, angiotensin and aldosterone
When blood pressure or sodium falls, the kidney releases renin. This leads to angiotensin II, which narrows blood vessels, and aldosterone, which makes the kidney keep sodium and lose potassium.
Natriuretic peptides
When the heart is stretched by too much volume, it releases ANP and BNP. They make the kidney lose sodium and water, the opposite of aldosterone.
Hormones the kidney makes
The kidney makes erythropoietin, which drives red blood cell production, and activates vitamin D, which helps absorb calcium. This is why chronic kidney disease causes anemia and bone disease.
| Hormone | Made in | Effect on the kidney |
|---|---|---|
| ADH | Hypothalamus, released by the pituitary | Keeps water |
| Aldosterone | Adrenal cortex | Keeps sodium, loses potassium |
| ANP and BNP | Heart | Loses sodium and water |
| Parathyroid hormone | Parathyroid glands | Keeps calcium, loses phosphate |
At the bedside
Many common drugs act on this system: ACE inhibitors and ARBs block angiotensin, spironolactone blocks aldosterone. Check potassium and creatinine after starting or changing them.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).