An older adult patient exhibit decreased antidiuretic hormone (ADH) responsiveness due to age-related endocrine changes. Based on this alteration, which complication is the patient most at risk for?

A. Antidiuretic hormone (ADH) normally promotes water reabsorption in the kidneys, helping the body maintain fluid balance. With decreased ADH responsiveness, the kidneys are less able to conserve water, leading to increased water loss in urine. Older adults are particularly vulnerable because age-related changes reduce renal concentrating ability, increasing the risk for dehydration, hypernatremia, and fluid volume deficits. B. Hyponatremia occurs when there is excess water relative to sodium, often due to overproduction of ADH or excessive fluid intake. In this case, the problem is reduced ADH responsiveness, which leads to water loss rather than retention, making hyponatremia unlikely. C. Fluid overload occurs when the body retains excessive water or sodium, increasing blood volume and potentially causing edema or heart strain. With decreased ADH activity, the body loses water, so fluid overload is not a typical complication. D. Hypertension is more closely related to vascular resistance, sodium retention, and cardiac output, not directly to reduced ADH responsiveness. Although dehydration can sometimes cause mild blood pressure fluctuations, it does not directly cause hypertension in this context.