Secondary Hypertension: Discovering the Underlying Cause.

Most patients with hypertension have no clear etiology and are classified as having primary hypertension. However, 5% to 10% of these patients may have secondary hypertension, which indicates an underlying and potentially reversible cause. The prevalence and potential etiologies of secondary hypertension vary by age. The most common causes in children are renal parenchymal disease and coarctation of the aorta. In adults 65 years and older, atherosclerotic renal artery stenosis, renal failure, and hypothyroidism are common causes. Secondary hypertension should be considered in the presence of suggestive symptoms and signs, such as severe or resistant hypertension, age of onset younger than 30 years (especially before puberty), malignant or accelerated hypertension, and an acute rise in blood pressure from previously stable readings. Additionally, renovascular hypertension should be considered in patients with an increase in serum creatinine of at least 50% occurring within one week of initiating angiotensin-converting enzyme inhibitor or angiotensin receptor blocker therapy; severe hypertension and a unilateral smaller kidney or difference in kidney size greater than 1.5 cm; or recurrent flash pulmonary edema. Other underlying causes of secondary hypertension include hyperaldosteronism, obstructive sleep apnea, pheochromocytoma, Cushing syndrome, thyroid disease, coarctation of the aorta, and use of certain medications.