Vasopressin · Grey Matter

Vasopressin (antidiuretic hormone, ADH) is the peptide hormone that tells the kidneys to keep water: when the blood becomes too concentrated or its volume falls, it makes the urine more concentrated and, at high levels, narrows blood vessels.

Vasopressin. Vasopressin (antidiuretic hormone, ADH) is the peptide hormone that tells the kidneys to keep water: when the blood becomes too concentrated or its volume falls, it makes the urine more concentrated and, at high levels, narrows blood vessels.

Like oxytocin it is made in the supraoptic and paraventricular nuclei of the hypothalamus and released from the posterior pituitary gland. Osmoreceptors near the hypothalamus detect a rise in the salt concentration of the blood of only a few percent and trigger its release together with thirst. In the kidney it acts on V2 receptors of the collecting ducts, which insert aquaporin-2 water channels into the cell membrane so that water is drawn back into the blood; on V1 receptors of blood vessels it causes constriction, hence its name.

Its absence shows as huge volumes of dilute urine. In central diabetes insipidus, damage to the hypothalamus, the stalk or the posterior pituitary stops vasopressin release, and a person may pass many litres a day and drink to match.

Alcohol inhibits its release, which is part of why drinking increases urination.

Inside the brain it also acts as a neuromodulator, linked in animals to social recognition, territorial behaviour and the stress response, where it helps CRH drive the HPA axis.

Questions: What happens when the posterior pituitary stops releasing vasopressin? Without vasopressin the collecting ducts of the kidney cannot insert their aquaporin water channels, so water that should be reclaimed leaves in the urine. The result is central diabetes insipidus: large volumes of dilute urine, often several litres a day, and intense thirst that keeps the person drinking to match. Its causes are damage to the hypothalamus, the stalk or the posterior pituitary (surgery, trauma, tumours), and it is treated with a synthetic analogue of the hormone.