Medical-Surgical Endocrine Practice Test

Central versus nephrogenic diabetes insipidus reflect where the problem lies and how it’s best treated. In central diabetes insipidus, there is a deficiency of ADH production or release from the hypothalamus/pituitary. The kidneys are capable of responding to ADH, so replacing it with desmopressin (DDAVP) normalizes water reabsorption and reduces urine volume, with careful monitoring of hydration and electrolyte status. In nephrogenic diabetes insipidus, ADH is adequate or even elevated, but the kidneys don’t respond to it due to receptor or collecting‑duct insensitivity (or drugs/toxic effects). Since the ADH signal can’t be used, giving desmopressin won’t effectively curb polyuria. Management aims to reduce free water loss and protect hydration: ensure sufficient fluids, use thiazide diuretics to induce mild volume depletion that paradoxically lowers urine output, and add NSAIDs to diminish prostaglandin-mediated diuresis. Desmopressin is avoided because it won’t help the kidney’s resistance to ADH. So the best answer aligns with a deficiency of ADH treated by replacement, versus renal insensitivity treated with hydration plus agents that reduce urine flow, rather than ADH replacement.