Progressive Care Nursing Certification (PCCN) Practice Exam

What is the effect of antidiuretic hormone (ADH) in the kidneys?

1. Concentrate the urine

2. Reabsorb potassium

3. Increase sodium loss in the urine

4. Dilute the urine

The correct answer is: Concentrate the urine

Antidiuretic hormone (ADH), also known as vasopressin, plays a crucial role in the regulation of water balance in the body. When released, it acts primarily on the kidneys to promote the reabsorption of water in the collecting ducts. This action leads to a decrease in urine volume and results in the production of concentrated urine. The mechanism involves the insertion of aquaporin channels into the membranes of the renal tubular cells, which facilitates the reabsorption of water back into the bloodstream, hence reducing water excretion. This is particularly important during times of dehydration or increased plasma osmolality, allowing the body to conserve water and maintain blood pressure and fluid balance. In contrast, other choices do not accurately describe the primary function of ADH. Potassium reabsorption is regulated by different mechanisms, primarily involving aldosterone. Increasing sodium loss in the urine is associated with other hormones like atrial natriuretic peptide (ANP) rather than ADH. Diluting the urine would indicate a decrease in water reabsorption, which is not the action of ADH. Thus, the correct answer highlights the critical role of ADH in concentrating urine through water reabsorption in the kidneys.