Which condition results from excessive secretion of antidiuretic hormone?

Which condition results from excessive secretion of antidiuretic hormone?

• A. SIADH
• B. Diabetes insipidus
• C. Hyperthyroidism
• D. Cushing syndrome

Answer: (A)

Excessive secretion of antidiuretic hormone causes the kidneys to retain water, lowering serum osmolality and diluting the blood. This leads to hyponatremia with inappropriately concentrated urine. The condition that fits this pattern is SIADH, the syndrome of inappropriate antidiuretic hormone secretion, where ADH keeps being released despite low serum osmolality, resulting in water retention and low sodium. Clinically you’d expect low serum sodium and low serum osmolality with high urine osmolality and often euvolemia. Diabetes insipidus would produce the opposite: large volumes of dilute urine due to insufficient ADH or renal insensitivity, leading to dehydration and hypernatremia. Hyperthyroidism and Cushing syndrome involve different hormonal axes and do not cause the water-retaining, hyponatremic state driven by excess ADH.

Excessive secretion of antidiuretic hormone causes the kidneys to retain water, lowering serum osmolality and diluting the blood. This leads to hyponatremia with inappropriately concentrated urine. The condition that fits this pattern is SIADH, the syndrome of inappropriate antidiuretic hormone secretion, where ADH keeps being released despite low serum osmolality, resulting in water retention and low sodium. Clinically you’d expect low serum sodium and low serum osmolality with high urine osmolality and often euvolemia.

Diabetes insipidus would produce the opposite: large volumes of dilute urine due to insufficient ADH or renal insensitivity, leading to dehydration and hypernatremia. Hyperthyroidism and Cushing syndrome involve different hormonal axes and do not cause the water-retaining, hyponatremic state driven by excess ADH.