Diabetes insipidus is caused by a lack of which hormone?

• A. ADH
• B. Insulin
• C. Cortisol
• D. Aldosterone

Answer: (A)

Diabetes insipidus results from a lack of antidiuretic hormone, ADH (vasopressin). ADH normally tells the kidneys’ collecting ducts to reabsorb water by inserting aquaporin-2 channels. When ADH is deficient or the kidneys don’t respond to it, water reabsorption drops, so the urine becomes very dilute and produced in large amounts. The body's response is to drink more, but the low-ADH state leaves you with polyuria and can raise serum osmolality. This is different from insulin, cortisol, or aldosterone deficiencies, which cause other problems (high blood sugar from lack of insulin; stress and energy issues from cortisol; sodium balance and blood pressure issues from aldosterone). The hormone responsible for DI is antidiuretic hormone.