High blood pressure (hypertension) is the most common medical disorder diagnosed in the United States. According to current estimates, 1 in 3 Americans has hypertension, but it is particularly common among blacks. A recent study in Americans found that 41 percent of blacks and 27 percent of whites had high blood pressure.

Even more alarming is the recognition that hypertension is becoming more and more resistant to the drugs used to treat it. Uncontrolled high blood pressure is an important underlying cause of heart attacks, strokes, kidney disease, and heart failure.

The majority of patients with hypertension need two or more classes of anti-hypertensive drugs, each lowering blood pressure through a different mode of action, to control their blood pressure. Blood pressure is defined as "resistant" or "unresponsive" if not controlled by three different medications. Using this definition, a panel of experts estimated that hypertension is now resistant to treatment in 20 percent to 30 percent of Americans, a near doubling of uncontrolled blood pressure over the past 12 years.

Your doctor needs to take several steps if your blood pressure is resistant to treatment:

• Verify that medications are being taken as prescribed
• Show that you have resistant hypertension by using sound techniques for measuring blood pressure—to document that your blood pressure in the doctor's office exceeds 140/90, or, if you have diabetes or chronic kidney disease, exceeds 130/90.
• If "white-coat hypertension" (blood pressure is high when measured in the doctor's office but not at home) is suspected, consider ambulatory blood pressure monitoring—wearing a device that records your blood pressure measurements throughout the day and night.
• Encourage perseverance with healthy lifestyle measures—weight-loss efforts and increased physical activity—while avoiding high salt intake and excessive alcohol consumption.
• Discontinue or limit substances that can raise blood pressure, such as non-steroidal anti-inflammatory agents, diet pills, oral contraceptives, decongestants, licorice, and ephedra.
• Screen for secondary causes of resistant hypertension. These include obstructive sleep apnea, renal artery stenosis, a narrowing of the aorta, and excessive secretion of hormones from the adrenal glands.

In the past, researchers considered the secretion of hormones from both tumors and overgrowths of portions of the adrenal glands to be uncommon causes of hypertension. But a tumor or overgrowth of cells in the adrenal cortex can cause overproduction of aldosterone, which is in fact a hormone that raises blood pressure. In recent years, studies have shown that primary aldosteronism (PA) may be responsible for about 10 percent of cases of unexplained hypertension and for about 20 percent of cases of resistant hypertension. PA can arise from either a tumor of the adrenal cortex or a generalized, bilateral overgrowth of adrenal cortex tissue. PA should be considered not only when hypertension is unresponsive, but also when:

• blood potassium levels are low spontaneously or when taking a diuretic.
• hypertension is present and there is a family history of early-onset hypertension, a stroke before the age of 40, or a first-degree relative with PA.

If you have any of these situations that suggest PA, you should ask for a referral to a hypertension specialist or an endocrinologist. The diagnosis can be made with a simple blood test and confirmed by a computed tomography (CT) scan of the adrenal. While most adrenal cortical tumors (adenomas) are benign, the CT scan can also identify larger tumors that are more likely to be malignant. Adrenal adenomas can be removed by laparoscopic surgery. A drug such as spironolactone is usually effective in controlling PA that's a result of generalized overgrowth of both adrenal glands.