Which pituitary hormone is deficient in central diabetes insipidus?

• A. Growth hormone
• B. Antidiuretic hormone (ADH)/vasopressin
• C. Prolactin
• D. ACTH

Answer: (B)

Central diabetes insipidus is due to a deficiency of antidiuretic hormone (ADH), also called vasopressin. ADH is made in the hypothalamus and released from the posterior pituitary; it tells the kidneys to conserve water by increasing water reabsorption in the collecting ducts. When ADH is deficient, the kidneys can’t concentrate urine, so large volumes of dilute urine are produced, and thirst increases as the body tries to replace lost water. This is specifically about water balance, unlike the other pituitary hormones listed—growth hormone affects growth and metabolism, prolactin stimulates lactation, and ACTH stimulates cortisol production. So the hormone missing in central diabetes insipidus is ADH.