A 28-year-old man comes to the physician with muscle weakness and headaches for the last 2 months. He denies palpitations, tremors, or increased sweating. His blood pressure is 190/120 mm Hg and his pulse is 68/min. His serum potassium level is 2.8 mEq/L. The patient's plasma renin activity is high and his serum aldosterone levels are elevated. A 24-hour urine collection shows increased potassium excretion. Which of the following is the most likely cause of this patient's symptoms?

Question

A 28-year-old man comes to the physician with muscle weakness and headaches for the last 2 months.  He denies palpitations, tremors, or increased sweating.  His blood pressure is 190/120 mm Hg and his pulse is 68/min.  His serum potassium level is 2.8 mEq/L.  The patient's plasma renin activity is high and his serum aldosterone levels are elevated.  A 24-hour urine collection shows increased potassium excretion.  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3cf6_2bd8_9249_efc354726464_MD0001_00 This patient has elevated serum aldosterone, a known cause of hypertension, hypokalemia, and muscle weakness. Hyperaldosteronism can be divided into primary and secondary etiologies. In primary hyperaldosteronism (ie, Conn's syndrome), an adrenal adenoma or bilateral adrenal hyperplasia causes excessive and unchecked aldosterone production that leads to feedback inhibition of renin secretion (ie, low renin level). Primary hyperaldosteronism can be excluded in this patient due to his increased plasma renin activity (Choice A). In secondary hyperaldosteronism, overproduction of aldosterone occurs secondary to increased renin synthesis, resulting in elevated renin and aldosterone levels. Causes of secondary hyperaldosteronism include renal artery stenosis (typically associated with fibromuscular dysplasia or atherosclerosis), diuretic use, malignant hypertension (which leads to microvascular damage and renal ischemia), and renin-secreting tumors. Renin-secreting tumors (reninomas) are rare, small, solitary, benign juxtaglomerular cell neoplasms. Reninomas should be strongly considered in patients with marked hyperreninemia and hypertension who clearly do not have renovascular disease. (Choice B) Pheochromocytomas are adrenal medullary tumors that secrete excessive catecholamines. High epinephrine levels can sometimes cause hypokalemia via β2-receptor stimulation and the resulting intracellular K⁺ shift. However, patients with pheochromocytomas typically present with episodic headaches, tachycardia (often sensed as palpitations), and increased sweating. (Choice D) A pituitary tumor (eg, an ACTH-secreting adenoma causing Cushing's disease) can result in secondary hypertension due to excess adrenal glucocorticoids (increases vascular sensitivity to adrenergic agents). The resulting hypertension suppresses the renin-angiotensin-aldosterone axis, leading to low levels of renin and aldosterone. (Choice E) Primary (essential) hypertension is not typically associated with severe hypertension, elevated levels of renin, or hypokalemia. Educational objective: Elevated serum aldosterone levels can manifest with hypertension, hypokalemia, and muscle weakness. Increased levels of both renin and aldosterone are indicative of secondary hyperaldosteronism, which can be caused by renovascular disease and renin-secreting tumors.

A 28-Year-Old Man Comes to the Physician with Muscle Weakness