The Posterior Pituitary Gland and Disorders of Vasopressin Metabolism

Abstract

The posterior pituitary gland, also known as the neurohypophysis, shares a name with the anterior pituitary but has indirect connection to the brain as the posterior pituitary contains the nerve endings of the vasopressin and oxytocin neurons which originate in the periventricular and supraoptic nuclei. Vasopressin is secreted from the posterior pituitary gland as is oxytocin. Disorders of vasopressin metabolism may cause increased or decreased urine formation and subsequent abnormalities in body water and serum osmolality and electrolytes. Rather than being controlled by secretions of the median eminence of the hypothalamus through the hypophyseotrophic portal system, these nerve endings in the posterior pituitary directly secrete their product into the general circulation. These neurons may be interrupted by trauma or surgery and the level of the interruption determines the outcome. If the pituitary stalk section is low some intact vasopressin neurons will remain as some terminate at the top of the pituitary stalk and diabetes insipidus may be mild or not occur. If the stalk section is high it is more likely that all vasopressin neurons will be affected and that diabetes insipidus will be permanent.