In central diabetes insipidus, which hormone is deficient?

In central diabetes insipidus, which hormone is deficient?

• A. Antidiuretic hormone (ADH/vasopressin)
• B. Aldosterone
• C. Cortisol
• D. Insulin

Answer: (A)

The key idea is that central diabetes insipidus stems from a deficiency of antidiuretic hormone (ADH), also called vasopressin. ADH is made in the hypothalamus and released by the posterior pituitary in response to high plasma osmolality or low blood volume. It acts on the kidney’s collecting ducts to promote water reabsorption by triggering aquaporin-2 channels, which concentrates the urine and reduces urine volume. When ADH is deficient, the kidneys cannot concentrate urine, leading to large volumes of dilute urine and increased thirst—classic central DI. Aldosterone, cortisol, and insulin have important roles in electrolyte balance, stress response, and glucose metabolism, respectively, but they do not regulate water reabsorption in the same acute, ADH-driven way. Thus their deficiencies do not cause the same water-diuresis pattern seen in central DI.

The key idea is that central diabetes insipidus stems from a deficiency of antidiuretic hormone (ADH), also called vasopressin. ADH is made in the hypothalamus and released by the posterior pituitary in response to high plasma osmolality or low blood volume. It acts on the kidney’s collecting ducts to promote water reabsorption by triggering aquaporin-2 channels, which concentrates the urine and reduces urine volume. When ADH is deficient, the kidneys cannot concentrate urine, leading to large volumes of dilute urine and increased thirst—classic central DI.

Aldosterone, cortisol, and insulin have important roles in electrolyte balance, stress response, and glucose metabolism, respectively, but they do not regulate water reabsorption in the same acute, ADH-driven way. Thus their deficiencies do not cause the same water-diuresis pattern seen in central DI.