Diabetes insipidus results from an inadequate release of which hormone?

• A. Aldosterone
• B. Calcitonin
• C. Insulin
• D. Antidiuretic hormone

Answer: (D)

Antidiuretic hormone controls water reabsorption in the kidney, acting on the collecting ducts to insert aquaporin channels and concentrate urine. When there isn’t enough ADH released, the kidneys reabsorb less water, producing large volumes of dilute urine and triggering increased thirst. This pattern defines diabetes insipidus from a deficiency of ADH, specifically central DI where the posterior pituitary fails to release adequate ADH. The other hormones don’t drive this condition: aldosterone mainly regulates sodium and water balance indirectly, calcitonin handles calcium regulation, and insulin controls glucose metabolism. So the inadequate release of antidiuretic hormone explains the polyuria and dilute urine seen in diabetes insipidus.