Primary hypertension describes high blood pressure that occurs as a standalone medical condition. Most high blood pressure in adults is due to primary hypertension. However, high blood pressure can also occur as a complication of another medical condition. This is secondary hypertension. Although secondary hypertension proves much less common than primary hypertension among adults, accurate diagnosis proves important because treating the underlying medical condition may lead to resolution of secondary hypertension.
Chronic Kidney Disease
The Mayo Clinic notes that several chronic kidney diseases can lead to secondary hypertension, including diabetic nephropathy, glomerulonephritis, polycystic kidney disease and hydronephrosis--blockage of urinary outflow by a kidney stone. Each of these disorders impairs the kidneys' ability to filter the blood and maintain normal water balance in the body. Fluid overload and high blood pressure frequently develop due to intrinsic kidney damage and malfunction.
Renal Artery Stenosis
As the primary site for maintaining water balance in the body, the kidneys contain mechanisms to monitor blood pressure. Renal artery stenosis--narrowing of the arteries that supply the kidneys--causes a local decrease in blood pressure within the kidneys. The kidneys respond to the low pressure via a series of chemical triggers that lead to increased water and sodium conservation. Hypertension develops due to increased total body water and salt. The National Institute of Diabetes and Digestive and Kidney Diseases explains that long-standing hypertension due to renal artery stenosis may lead to kidney damage, often exacerbating high blood pressure.
Pheochromocytoma
Pheochromocytomas are tumors that arise from the tissues of the innermost region of the adrenal glands, the adrenal medulla. The tumors produce the hormones epinephrine and norepinephrine, which cause dramatic increases blood pressure. "The Merck Manual for Healthcare Professionals" notes that approximately 55 percent of people with pheochromocytoma have persistent, markedly elevated blood pressure. Among the remaining 45 percent, the blood pressure spikes multiple times throughout the day. The text points out that roughly one out of every 1,000 people with high blood pressure has a pheochromocytoma.
Aldosteronism
Cells of the outer portion of the adrenal glands, the adrenal cortex, produce the hormone aldosterone, which helps regulate blood pressure by influencing body water and salt content. Overproduction of aldosterone, or aldosteronism, causes excessive conservation of salt by the kidneys, leading to increased total body water and high blood pressure. The Mayo Clinic reports that the most common causes of adrenal overproduction of aldosterone include benign and cancerous tumors of the adrenals, and adrenal tissue overgrowth, or adrenal hyperplasia. Surgical removal of adrenal tumors and medications to block the effects of aldosterone on the kidneys serve as the two primary forms of treatment for aldosteronism.
