In most cases of high blood pressure (hypertension), there is no known cause. About 6% of the time, however, high blood pressure is caused by another condition or disease. When this happens, it is called secondary hypertension.
Most of the conditions that cause secondary hypertension involve the overproduction of one of the body's hormones. Some of the medical problems that can cause secondary hypertension include:
Kidney disease. Secondary hypertension can be related to damaged kidneys or to an abnormal narrowing of one or both renal arteries. The renal arteries are the major blood vessels that bring blood to each kidney. When the kidney's blood supply is reduced by a narrowing (called renal artery stenosis), the kidney produces high levels of a hormone called renin. High levels of renin trigger the production of other substances in the body that raise blood pressure, particularly a molecule called angiotensin II.
Adrenal disease. The adrenal glands sit on top of the kidneys and produce several hormones that help regulate blood pressure. Sometimes, one or both adrenal glands make and secrete an excess of one of these hormones.
Three different types of adrenal gland conditions cause high blood pressure:
Pheochromocytoma. A tumor of the adrenal gland that overproduces the hormones epinephrine (adrenalin) and norepinephrine (noradrenalin).
Hyperaldosteronism (also called Conn's syndrome). Both adrenal glands can overproduce the salt-retaining hormone aldosterone or it can arise in a benign adrenal tumor.
Hypercortisolism (also called Cushing's syndrome). Both adrenal glands can overproduce the hormone cortisol or it can arise in a benign or malignant tumor.
Hyperparathyroidism. A hormone called parathormone is made by four tiny glands in the neck called parathyroid glands. If the glands produce too much hormone, calcium levels in the blood increase. People with hyperparathyroidism are more likely to have high blood pressure. The exact reason for this association is not known.
Other rare causes of secondary hypertension include:
Acromegaly. A pituitary tumor that produces too much growth hormone.
An adrenocorticotrophic hormone (ACTH) producing tumor of the pituitary gland. The pituitary normally makes a small amount of ACTH daily. Excess ACTH production and secretion causes the adrenal glands to overproduce cortisol, raising blood pressure.
An ACTH producing cancer of the lung.
Coarctation of the aorta, a malformation of the major blood vessel that carries blood from the heart to the rest of the body.
High blood pressure may be a side effect of medication, such as hormonal contraceptives and non-steroidal anti-inflammatory agents (NSAIDs).