High Blood Pressure
Causes of Primary Hypertension
Hypertension is referred to as essential (primary) when the doctor is unable to identify a specific cause. It is by far the most common type of high blood pressure. The causes of this type, while unknown, are likely to be a complex combination of genetic, environmental, and other factors.[For risk factors of developing primary hypertension, see the Risk Factors section of this report.]
Genetic Factors. A number of genetic factors or interactions between genes play a major role in essential hypertension. Genes under investigation include:
- Genes that regulate a group of hormones known collectively as the angiotensin-renin-aldosterone system. This system influences all aspects of blood pressure control, including blood vessel contraction, sodium and water balance, and cell development in the heart.
- Genes that cause abnormalities of the sympathetic nervous system. This is the part of the autonomic nervous system that controls heart rate, blood pressure, and the diameter of the blood vessels.
Causes of Secondary Hypertension
Secondary hypertension is caused by an underlying medical condition or other factor (such as medications) that elevates blood pressure. Many different medical conditions are associated with secondary hypertension. These conditions can also make high blood pressure more difficult to control. They include:
Diabetes. Hypertension is strongly associated with diabetes, both type 1 and type 2. Kidney damage (diabetic nephropathy) is generally the cause of high blood pressure in people with diabetes.
Kidney Disease. Kidney disease is the most common cause of secondary hypertension, particularly in older people. In addition to diabetic nephropathy, many other types of kidney diseases can cause hypertension. Renal artery stenosis involves the narrowing of the renal artery and is usually caused by atherosclerosis. Other types of kidney disease associated with hypertension are polycystic kidney disease and renal parenchymal disease.
Coarctation of the Aorta. Coarctation of the aorta is a birth defect that causes narrowing of the aorta, the main artery of the heart.
Endocrine Disorders. Adrenal tumors (pheochromocytoma, aldosteronism), thyroid disorders, and Cushing syndrome can all cause secondary hypertension.
Medications. Many different prescription and over-the-counter drugs can temporarily raise blood pressure or worsen existing high blood pressure. They include:
- Corticosteroids when given by mouth or intravenously
- Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Motrin), naproxen (Aleve), and aspirin
- Cold medicine decongestants containing pseudoephedrine can increase blood pressure in people with high blood pressure, although they appear to pose no danger for those with normal blood pressure.
- Oral contraceptives (birth control pills) increase the risk for high blood pressure, particularly in women who are older than 35 years, obese, smokers, have strong family history of hypertension, or some combination of these factors. Stopping the pill nearly always reduces blood pressure.