Symptoms such as dry mouth and dehydration in DI are due to what underlying problem?

Symptoms such as dry mouth and dehydration in DI are due to what underlying problem?

• A. Inability of the kidneys to concentrate urine leading to free water loss
• B. Excess ADH causing water retention
• C. Excess aldosterone causing sodium retention
• D. Insulin deficiency

Answer: (A)

In diabetes insipidus, the kidneys fail to concentrate urine because ADH (vasopressin) signaling is inadequate. ADH normally binds to receptors in the collecting ducts and triggers insertion of aquaporin-2 channels, allowing water to be reabsorbed and urine to become concentrated. When ADH action is deficient or the kidneys don’t respond to it (central or nephrogenic diabetes insipidus), a large volume of dilute urine is produced. This free water loss leads to dehydration and dry mouth as the body tries to compensate by increasing thirst. The other options don’t fit because excess ADH would cause water retention and concentrated urine, excess aldosterone would mainly affect sodium and water balance differently, and insulin deficiency causes osmotic diuresis from glycosuria rather than an inability to concentrate urine.

In diabetes insipidus, the kidneys fail to concentrate urine because ADH (vasopressin) signaling is inadequate. ADH normally binds to receptors in the collecting ducts and triggers insertion of aquaporin-2 channels, allowing water to be reabsorbed and urine to become concentrated. When ADH action is deficient or the kidneys don’t respond to it (central or nephrogenic diabetes insipidus), a large volume of dilute urine is produced. This free water loss leads to dehydration and dry mouth as the body tries to compensate by increasing thirst. The other options don’t fit because excess ADH would cause water retention and concentrated urine, excess aldosterone would mainly affect sodium and water balance differently, and insulin deficiency causes osmotic diuresis from glycosuria rather than an inability to concentrate urine.