The causes of high blood pressure are divided into two broad groups. The first group is called primary, or essential, hypertension. This is the most common form of high blood pressure, and the exact cause is not clearly understood. However, it is believed to be due in part to a combination of genetic and environmental factors. Having diabetes may amplify some of these factors. In people with Type 1 diabetes, kidney disease is also believed to play a central role in the progression of high blood pressure. In people with Type 2 diabetes, obesity and insulin resistance may be important factors. However, it should be noted that some studies show a stronger connection between high blood pressure and diabetes in people with Type 2 diabetes who are thin.
The second form of high blood pressure is appropriately called secondary hypertension, and while it is less common, it is at times curable without the need for long-term drug treatment. There is a long list of conditions and medicines that can cause secondary hypertension. Kidney disease is probably the most common form of secondary hypertension. The kidneys are supplied by two main kidney arteries, and when a kidney artery develops a narrowing, the kidney “believes” your blood pressure is too low. It then sends signals to raise your blood pressure inappropriately. This is called renal (kidney) artery hypertension. Opening the blocked artery with a balloon and stent (a sort of medical scaffolding) can cure this type of high blood pressure in some cases.
Sleep apnea, thyroid disease, and certain hormone-producing tumors can lead to high blood pressure as well. Some prescription and over-the-counter drugs can also raise blood pressure. Steroids, non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen), and certain cold medicines (including those containing pseudoephedrine) are a few of the more common culprits. Oral contraceptives are also associated with high blood pressure in women, especially women who smoke or are obese.
High blood pressure is often called “the silent killer,” because even while it is damaging your organs, it usually does not cause any symptoms. That’s why an important part of the initial evaluation of high blood pressure is identifying any damage that has already been caused by it. Constantly pumping against a very high pressure can strain the heart and cause it to become enlarged, or hypertrophied. An enlarged heart is associated with an increased risk of heart attack, heart failure, sudden death, and stroke. An electrocardiogram or echocardiogram (heart ultrasound) can identify this complication. Constantly filtering under high pressure can lead to kidney damage, resulting in abnormal kidney function and the leakage of protein into the urine. These types of complications of high blood pressure are called end-organ damage, but they can potentially improve with aggressive treatment of the high blood pressure.
Essential hypertension generally progresses very slowly over years. This is in sharp contrast to secondary hypertension, which more frequently progresses quickly over months, weeks, or even days, leading to a rapid rise in blood pressure. This is termed accelerated hypertension and can be associated with symptoms such as headache, nausea, visual problems, confusion, or drowsiness. Anyone with rapidly worsening blood pressure and significant symptoms should be evaluated immediately by their physician. The pace of the blood pressure rise can be an important clue to the cause.
Treating high blood pressure
Once high blood pressure is diagnosed, a treatment program should begin immediately. In cases where the blood pressure is very elevated (as in stage 2 hypertension, with systolic blood pressure higher than 160 mm Hg), drug therapy is often initiated right away while lab tests and x-ray studies are obtained. When a person is found to have secondary hypertension, treatment is directed at the cause. For example, if a person is found to have a kidney artery blockage causing hypertension, he will be considered for a procedure to open the blocked kidney artery.