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Hypertension is one of the most prevalent conditions on the planet. Scientists estimate that it affects 30-45% of adults, somewhere over a billion people! Hypertension is the chronic elevation of blood pressure. The CDC defines it as above 130 mmHg systolic or above 80 mmHg diastolic. For short periods of time, elevated blood pressure can be useful – for exercise, say. People can have high blood pressure for years without symptoms. For long periods of time, however, hypertension is deadly serious. Unfortunately, living with high blood pressure can lead to a host of problems. Hypertension can lead to heart attack and stroke, and damage to the heart, brain, kidneys, and even eyes!
Everyone is at risk of high blood pressure. In America, men have a higher likelihood of hypertension. There are also differences in ethnicity and race, non-Hispanic Black or African American adults are at the highest risk. Unfortunately, even the lowest risk categories still have around a 40% prevalence of high blood pressure. Clearly this is a large issue in America and around the world.
The big culprit behind hypertension is the Renin–angiotensin–aldosterone system (RAAS). RAAS is a critical system for maintaining blood pressure. It regulates two primary factors: the amount of blood and how constricted blood vessels are. It does this through the kidney, liver, and adrenal gland (just above the kidneys). In response to body signals, the kidneys release an enzyme to the liver. In response, the liver produces the hormone angiotensin I. Another enzyme, angiotensin-converting enzyme (ACE) converts this to angiotensin II, which goes to work.
Angiotensin II has wide-ranging effects to increase sodium and water retention. It also causes blood vessels to constrict. Angiotensin II is very short-lived, only lasting 1-2 minutes. One of its many effects is to get the adrenal gland to produce aldosterone. Aldosterone has similar effects as angiotensin II, but instead of a few minutes, it takes hours or days to take effect. The end result is that two major hormones – one fast-acting and one slow-acting – cause high blood pressure.
There are many medications available to fight hypertension. Most of these, such as diuretics or beta-blockers, have wide-ranging side effects. This is because they are system-wide, indiscriminate actors on the body. Beta-blockers, for instance, slow the heart. This is helpful in lowering blood pressure but obviously leads to other effects on the body. RAAS-acting specific medications may be more helpful in combating hypertension with minimal side effects. ACE inhibitors, for instance, stop the fast-acting angiotensin II from having its effect on the body. This targeted approach to hypertension can lead to fewer side effects in some patients. Unfortunately, by acting on only the fast-acting portion of RAAS, they must be taken daily. Even worse, a few missed doses can have longer-term effects on blood pressure. Luckily, researchers are investigating other targeted methods of reducing the effect of RAAS, and blood pressure! Keep an eye out for a clinical research study to help investigate this exciting part of the fight against hypertension.
Written by: Benton Lowey-Ball, B.S. Behavioral Neuroscience
Fountain, J. H., & Lappin, S. L. (2017). Physiology, renin angiotensin system.
National Center for Chronic Disease Prevention and Health Promotion, Division for Heart Disease and Stroke Prevention. (September 27, 2027). Facts about hypertension. U.S. Department of Health and Human Services. https://www.cdc.gov/bloodpressure/facts.htm