What Causes High Blood Pressure?

In 85-90% of the cases of high blood pressure (hypertension), no specific underlying cause for the raised blood pressure is found even after thorough evaluation. Such cases are referred to as essential hypertension or primary hypertension. There are certain risk factors, which increases the chance of either having the primary hypertension or developing it in the future.

The remaining 10-15% of the cases of raised blood pressure are due to a specific disease that secondarily results in elevation of the blood pressure. Such cases are referred to as secondary hypertension. There are numerous diseases which can result in raised blood pressure. However, only the most common causes of secondary hypertension are mentioned here.

Essential Hypertension

The table given below lists the most important risk factors for essential hypertension. The presence of these risk factors does not guarantees raised blood pressure, but only increases the likelihood of having high blood pressure. The more the risk factors presents, the higher the chance of having high blood pressure or developing it in the future.

Table 1: Risk Factors for Essential Hypertension

Old Age and Gender	Increasing Age Predisposes to High Blood Pressure. Men are more likely to develop hypertension than women.
Family History	2/3^rd of people with essential hypertension have family history of hypertension. So high blood pressure in family members increases the risk of developing hypertension.
Ethnicity	African-American people more likely to develop high blood pressure compared to Caucasians. Also there hypertension is likely to be more severe.
Smoking	Cigarette smoking is a well known risk factor for developing hypertension. It is also a risk factor for many other cardiovascular diseases.
Alcohol	Drinking excessive amount of alcohol can cause high blood pressure.
Lack of Physical Activity	Sedentary lifestyle with very little physical activity increases the risk of developing hypertension.
Obesity	Excessive body weight (BMI > 25 kg/m²) increases the risk of having high blood pressure.
Unhealthy Diet	Diet low in fruits, vegetables, fibers and high in saturated and total fats and salt can cause high blood pressure (e.g. fast foods etc.)
Increased Salt Intake	High dietary intake of common salt (NaCl) is a risk factor for high blood pressure.
Others	Stress, Coffee, Diabetes
*Unknown Factors*	Many yet unknown factors may also contribute to high blood pressure.

Secondary Hypertension

The table given below lists some of the most common causes of secondary hypertension. Generally, secondary hypertension is due to kidney dysfunction or hormonal disturbances or a side effect of medications. Differentiating essential hypertension from secondary hypertension is very important because secondary hypertension can be cured if the primary condition causing the raised blood pressure is curable.

Table 2: Common Causes of Secondary Hypertension

Kidney Dysfunction (Renal Causes)	Renal Artery Stenosis, Polycystic Kidney Disease, Glomerulonephritis, Chronic Pyelonephritis, Renal Tumors, etc.
Hormonal Disturbances (Endocrine Causes)	Pheochromocytoma, Acromegaly, Hyperparathyroidism, Hypothyroidism, Hyperthyroidism, Cushing’s Syndrome, Conn’s Syndrome, etc.
Drugs (Medications)	Oral Contraceptive Pills, Anabolic Steroids, Corticosteroids, Decongestants, Appetite suppressants, NSAIDs etc. Illegal Drugs like Cocaine, Amphetamine
Others	Coarctation of Aorta, Obstructive Sleep Apnea, Genetic Diseases

The description of the disease conditions mentioned in the table are:

Renal Artery Stenosis (Renovascular Hypertension). Narrowing of the artery that supplies blood to the kidneys. Kidneys perceive lower blood pressure and increase salt and water retention to raise the blood pressure.
Polycystic Kidney Disease. Genetic disorder characterized by presence of numerous cysts in the kidneys.
Glomerulonephritis. The functional unit of the kidney is the glomerulus. Damage to these units is known as glomerulonephritis.
Chronic Pyelonephritis. Kidney inflammation and damage caused by repeated infection (most commonly) or due to other causes.
Renal Tumors. Tumors in the kidneys.
Pheochromocytoma. Epinephrine and Norepinephrine releasing tumor of the adrenal glands.
Acromegaly. Abnormally increased levels of growth hormones in the body. Often due to a benign tumor in pituitary gland.
Hyperparathyroidism. Increased levels of parathyroid hormone in the body.
Hypothyroidism, Hyperthyroidism. Low and High levels (respectively) of thyroid hormone.
Cushing’s Syndrome. Occurs due to excess levels of cortisol for prolonged time.
Conn’s Syndrome. Increased levels of the hormone aldosterone due to an aldosterone producing tumor.
Coarctation of Aorta. In this condition there is narrowing of a segment of aorta. Since renal artery originates distal to this narrowing, the pressure in this vessel is low, causing salt and water retention by the kidneys.
Obstructive Sleep Apnea. Narrowing of airway resulting in a pause in breathing (apnea) or decreased breathing (hypopnea) for a short period of time when a person in asleep.

Essential Hypertension

Secondary Hypertension

Same Category