Advanced Oncology Certified Nurse Practitioner (AOCNP) Certification Practice Test

Which condition might result in hyponatremia due to excess water retention?

1. Hyperaldosteronism

2. Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

3. Acute renal failure

4. Diabetes insipidus

The correct answer is: Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is associated with hyponatremia primarily because it leads to an excess of antidiuretic hormone (ADH) in the bloodstream. Elevated levels of ADH promote reabsorption of free water in the kidneys, resulting in diluted serum sodium levels. This condition disrupts the normal balance of water and sodium in the body, causing the sodium concentration to fall, hence leading to hyponatremia. In contrast, hyperaldosteronism typically results in sodium retention and potassium loss, which does not lead to water retention in the same manner as SIADH. Acute renal failure may contribute to alterations in sodium balance, but it can manifest differently depending on the underlying cause, potentially leading to various sodium levels rather than a consistent state of hyponatremia due to excess water retention. Diabetes insipidus is characterized by inadequate ADH action, leading to loss of water and potentially hypernatremia rather than hyponatremia. Thus, SIADH stands out as the specific condition that directly causes hyponatremia through mechanisms of excessive water retention.