High Blood Pressure
An in-depth report on the causes, diagnosis, treatment, and prevention of high blood pressure.
Beta Blockers; Calcium Channel Blockers; Hypertension
Hypertension is referred to as essential, or primary, when the physician is unable to identify a specific cause. It is by far the most common type of high blood pressure. The causes of this type are unknown but are likely to be a complex combination of genetic, environmental, and other factors.
Genetic Factors. A number of genetic factors or interactions between genes play a major role in essential hypertension. Experts appear to have located the chromosomes (13 and 18) that house the genes responsible for blood pressure regulation, although pinning down the range of specific genes involved in hypertension is more difficult.
Abnormalities in the Angiotensin-Renin-Aldosterone System. Genes under intense study are those 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.
Experts believed that this system evolved millions of years ago to protect early humans during drought or stress by retaining salt and water and narrowing blood vessels to ensure adequate blood flow and repair injured tissue. With industrialization, however, this system wreaks havoc on modern humans by intensifying the effects of our high-salt diets and sedentary lifestyle. Of particular importance in these harmful responses are the hormone aldosterone and a peptide (which are components of proteins) called angiotensin II.
Inherited Abnormalities in the Sympathetic Nervous System. Studies suggest that some people with essential hypertension may inherit 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.
Insulin Resistance and Type 2 Diabetes. Hypertension is strongly associated with diabetes, both type 1 and both 2. Kidney damage is generally the cause of high blood pressure in type 1 diabetes. Obesity and insulin resistance are the factors associated with hypertension in type 2 diabetes, the more common type. People with type 2 diabetes generally have normal or high levels of insulin, a critical hormone in the metabolism of sugar. However, they are unable to use the insulin, the condition called insulin resistance. Without insulin, blood glucose (sugar) levels rise, the hallmark of diabetes.
Some research indicates that obesity is the one common element linking insulin, type 2 diabetes, and high blood pressure. Obesity is common in both type 2 diabetes and hypertension. Oddly, however, studies have found a stronger association between hypertension and insulin resistance in thin patients as well as overweight people with type 2 diabetes. Some research indicates that insulin resistance may cause sodium retention, a contributor to high blood pressure.
In any case, regardless of the causal connections, people who have both insulin resistance or full-blown diabetes plus hypertension have a significantly greater chance for heart attack, kidney disease, and stroke than people who have only high blood pressure.
Obesity. Obesity on its own has a number of possible effects that could lead to hypertension. It may blunt certain actions of insulin that open blood vessels, and it may cause structural changes in the kidney and abnormal handling of sodium. It is also associated with alterations in the systems that regulate blood flow.
Low Levels of Nitric Oxide. The gas nitric oxide can be produced in the body, where it affects the smooth muscles cells that line blood vessels; it helps keep them relaxed, flexible. It may also help prevent blood clotting. Low levels of nitric oxide have been observed in people with high blood pressure (particularly in African Americans) and may be an important factor in essential hypertension.
Secondary hypertension has recognizable causes, which are usually treatable or reversible.
Medical Conditions. A number of medical conditions can cause secondary high blood pressure:
Medications. Certain prescription and over-the-counter drugs can cause temporary high blood pressure. Some include the following:
Alcohol, Cigarettes, and Coffee
Other Causes of Secondary High Blood Pressure. Temporary high blood pressure can result from a number of other conditions or substances.