DISORDERS OF THE NEUROHYPOPHYSIS, DIABETES MELLITUS CAUSED BY ARGININE VASOPRESSIN DEFICIENCY AND ITS DIFFERENTIAL DIAGNOSIS

Abstract

The neurohypophysis, or posterior pituitary, is formed by axons that originate in large cell bodies in the supra optic and paraventricular nuclei of the hypothalamus. It produces two hormones: (1) arginine vasopressin (AVP), also known as antidiuretic hormone, and (2) oxytocin. AVP acts on the renal tubules to reduce water loss by concentrating the urine. Oxytocin stimulates postpartum milk letdown in response to suckling. AVP deficiency causes diabetes insipidus (DI), which is characterized by the production of large amounts of dilute urine. Excessive or inappropriate AVP production predisposes to hyponatremia if water intake is not reduced in parallel with urine output.