Vasopressins

Vasopressins, also known as antidiuretic hormone (ADH), are peptide hormones produced by the hypothalamus and released by the posterior pituitary gland. Their primary function is to regulate water balance in the body. Vasopressin acts on the kidneys, specifically on the collecting ducts and distal convoluted tubules, increasing their permeability to water. This enhanced permeability allows more water to be reabsorbed from the filtrate back into the bloodstream, thus concentrating the urine and reducing water loss.

The release of vasopressin is controlled by the body's osmotic pressure. When the blood becomes more concentrated (e.g., due to dehydration), osmoreceptors in the hypothalamus detect this change and signal the posterior pituitary to release vasopressin. Conversely, when blood is diluted, vasopressin release is suppressed.

Beyond its role in water balance, vasopressin also plays a part in blood pressure regulation. It causes vasoconstriction, meaning it narrows blood vessels, which can increase blood pressure. This effect is more pronounced at higher concentrations. Vasopressin is also implicated in social behaviors, bonding, and reproductive functions in various species, though its precise role in humans is still an area of active research. Disruptions in vasopressin levels or its receptor function can lead to conditions like diabetes insipidus, characterized by excessive thirst and urination.