endocrine and metabolic disorders
Syndrome of Inappropriate ADH Secretion (SIADH)
Pathophysiology of SIADH
Vasopressinis a hormone produced by the posterior pituitary to help control fluid homeostasis. The hormone increases water reabsorption in the distal nephron, producing a concentrated urine and diluted plasma.Vasopressinrelease is stimulated by any of the following: Increased plasma osmolality Decreased blood volume Decreased blood pressure Stress Certain medications Low plasma osmolality inhibitsvasopressinsecretion, allowing the kidneys to produce dilute urine. release is inappropriate in the presence of normal or low plasma osmolality and normal or high blood volume and blood pressure. In such cases, the water inappropriately retained by the kidneys ultimately causes Euvolemic hyponatremia , in which total body sodium and thus extracellular fluid (ECF) volume are normal or near normal; however, total body water is increased. 