When should a secondary cause of hypertension be suspected and evaluated?
Evaluation for secondary causes of hypertension should be initiated based on history, physical exam, laboratory results, or clinical suspicion.
Anyone with difficult-to-correct or persistent hypokalemia should be suspected of secondary hypertension. Primary hyperaldosteronism is the most common cause of secondary hypertension. It is usually a bilateral adrenal hyperplasia. Not all patients have hypokalemia, and this may present with low normal potassium levels. Hypercortisolism (Cushing’s syndrome or disease) is a relatively rare form of secondary hypertension and shows a strong female predominance. It presents with a picture of central obesity and thin extremities, which is different from obesity, and, biochemically, will be associated with hypokalemia and metabolic alkalosis. It can easily be mistaken for primary aldosteronism until the hormone levels for aldosterone and cortisol are obtained. Pheochromocytomas are also an uncommon form of secondary hypertension. Incidental adrenal masses are frequently found by computed tomography scan, but very few have biochemical evidence for a pheochromocytoma. Clinical signs of a pheochromocytomas include labile BP and orthostatic hypotension, findings that are also associated with poor sleep quality, and this should always be sought in the patient’s history. Additional symptoms include waking in the night with very high pressures and sweats; in fact, it is the most common secondary cause of hypertension associated with orthostatic hypotension. Apart from fibromuscular dysplasia, renal artery stenosis is a manifestation of atherosclerotic disease found in patients with extensive atherosclerosis either from hypercholesterolemia or from smoking.