Advanced Oncology Certified Nurse Practitioner (AOCNP) Certification Practice Test

In the context of SIADH, what abnormal function do malignant cells exhibit?

1. Decreased ADH secretion

2. Increased sodium excretion

3. Autonomous ADH synthesis and secretion

4. Inhibited vasopressin receptor activity

The correct answer is: Autonomous ADH synthesis and secretion

In the context of Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH), malignant cells can exhibit autonomous synthesis and secretion of antidiuretic hormone (ADH), also known as vasopressin. This abnormal function contributes to the characteristic symptoms of SIADH, such as hyponatremia and fluid retention. When certain tumors, especially small cell lung cancer and other neuroendocrine tumors, produce ADH independent of the body's normal regulatory mechanisms, the result is an inappropriate increase in water retention, which then leads to dilutional hyponatremia. The autonomous nature of ADH production means that these malignant cells can produce the hormone without the usual triggers, such as increased plasma osmolality or decreased blood volume, that would normally stimulate its secretion. This overproduction disrupts the balance of fluids in the body and can create serious clinical challenges, necessitating careful monitoring and management of electrolyte levels in affected patients. Understanding this mechanism is crucial for healthcare providers managing patients with malignancies associated with SIADH.