Diabetes Insipidus (DI) is a deficiency in the production of which hormone?

• A. Aldosterone
• B. Glucose
• C. Vasopressin
• D. Prolactin

Answer: (C)

Diabetes insipidus is caused by a deficiency of vasopressin, the antidiuretic hormone. Vasopressin is produced in the hypothalamus and released from the posterior pituitary in response to high plasma osmolality. It acts on the kidney’s collecting ducts to promote water reabsorption by inserting aquaporin-2 channels, concentrating the urine and reducing water loss. When vasopressin production or action is deficient, the kidneys fail to concentrate urine, resulting in large volumes of dilute urine and thirst. Aldosterone, glucose, and prolactin do not drive this condition, which is why vasopressin is the correct choice.