A 30-year-old woman presents to the clinic with complaints of frequent headaches, fatigue, and muscle weakness over the past several months. She has also experienced episodes of palpitations and increased urination. Her blood pressure has consistently been elevated, averaging 160/100 mm Hg over the last three visits. On today’s measurement, the blood pressure is 158/98, and the other vital signs are normal. Physical examination is unremarkable. Laboratory tests reveal the following:
A CT scan of the abdomen reveals a 2.5 cm mass in the right adrenal gland. Which of the following is the most appropriate next step in the management of this patient?
D) Plasma renin activity and aldosterone concentration
This patient's clinical presentation, including hypertension, hypokalemia, and the presence of an adrenal mass, is highly suggestive of primary hyperaldosteronism (Conn syndrome). Primary hyperaldosteronism is characterized by excessive secretion of aldosterone, usually due to an adrenal adenoma or bilateral adrenal hyperplasia. This condition leads to sodium retention, potassium excretion, and secondary hypertension.
To confirm the diagnosis, the best next step is to measure plasma renin activity (PRA) and plasma aldosterone concentration (PAC). In primary hyperaldosteronism, the PAC is elevated, and the PRA is suppressed, resulting in a high PAC/PRA ratio (typically >20). A PAC >15 ng/dL along with a high PAC/PRA ratio strongly suggests primary hyperaldosteronism.
Answer choice A: Computed tomography angiography of the abdomen, is incorrect. Computed tomography angiography of the abdomen is used to evaluate renal artery stenosis or fibromuscular dysplasia, which can cause secondary hyperaldosteronism, but this is not the first step given the patient's presentation.
Answer choice B: Dexamethasone suppression test, is incorrect. A dexamethasone suppression test is used to diagnose Cushing syndrome, which presents with features such as central obesity, purple striae, and glucose intolerance, which are not seen in this patient.
Answer choice C: Plasma fractionated metanephrines, is incorrect. Plasma fractionated metanephrines are measured to evaluate for pheochromocytoma, which can cause hypertension and palpitations but does not typically present with hypokalemia or an adrenal mass that suggests hyperaldosteronism.
Answer choice E: Urine potassium excretion by 24-hour collection, is incorrect. Urine potassium excretion by 24-hour collection can help evaluate potassium loss but is not the best initial test for diagnosing primary hyperaldosteronism.
Key Learning Point
In a patient with hypertension, hypokalemia, and an adrenal mass suggestive of primary hyperaldosteronism, the best next step is to measure plasma renin activity and aldosterone concentration to confirm the diagnosis.
