The posterior pituitary serves as a site for the secretion of two neurohypophysial hormones vasopressin and oxytocin directly into the blood.
Vasopressin is derived from a preprohormone precursor that is synthesised in the hypothalamus and stored in vesicles at the posterior pituitary.
The two primary functions of vasopressin are to retain water in the body and to constrict blood vessels
Vasopressin regulates the body’s retention of water by acting to increase water reabsorption in the kidneys collecting ducts. It is a peptide hormone that increases water permeability of the kidneys collecting duct and distal convoluted tubules.
It increases peripheral vascular resistance, which in turn increases arterial blood pressure.
It plays a key role in homeostasis, by regulation of water , glucose and salts in blood.
Oxytocin is produced by the paraventricular nucleus of the hypothalamus and released by the posterior pituitary.
It plays an important role in social bonding, sexual reproduction and during childbirth.