Hypertension – Causes and Lab Testing

Many people suffer from hypertension, a condition characterized by a continuous rise in blood pressure that places undue strain on the heart. Also called high blood pressure, this condition can lead to more serious heart complications over time and cause damage to other organs, including the eyes, brain, and kidneys. In the US, 46% of adults have hypertension.  

Blood pressure (BP) refers to the force exerted by the blood on the artery walls. This pressure depends on the heart’s contraction rate and strength as it pumps blood as well as the blood flow resistance through the arteries. The diameter and elasticity of the blood vessels, as well as the blood volume that flows through them, influence the blood flow resistance. The narrower the arteries and the larger the volume of blood flowing through them, the higher the blood pressure gets. Living a healthy lifestyle is an effective way to delay or prevent high blood pressure.  

It’s normal for blood pressure to rise and fall throughout the day, depending on the activity level of the person and his physical and emotional stress. The autonomic nervous system is responsible for controlling blood pressure, but it’s also influenced by different hormones such as aldosterone, catecholamine, and angiotensin II.  

Two pressures are considered when measuring blood pressure, which is measured in millimeters of mercury. Systolic pressure refers to the force that the heart exerts on the blood vessel walls when pumping blood. Diastolic pressure, on the other hand, refers to the force in between heartbeats, a period in which the heart relaxes. These two pressures are commonly written or heard as systolic over diastolic pressure. For example, a 120/80 mm HG blood pressure reflects 120 systolic pressure and 80 diastolic pressure.  

Medical professionals can’t provide a conclusive diagnosis after taking a single measurement of blood pressure. In most cases, multiple readings are performed over a period of days, and if these measurements remain consistently high, then the doctor can diagnose the patient as having hypertension.  

Normally, the diastolic pressure mirrors the systolic pressure. As people get older, however, the diastolic pressure can level out. There’s also a form of hypertension that primarily involves systolic pressure, and this condition is more common among the elderly. People who have suffered from blood pressure for a long period are at a greater risk of damage to the heart and other organs.  

Common signs and symptoms  

Hypertension rarely manifests any symptoms for most people. Many people suffer from hypertension for many years without knowing it. High blood pressure only becomes apparent when getting regularly checked by a health professional. Even patients who have life-threatening levels of blood pressure may not exhibit any symptoms. If any, they will only suffer from dizziness, headaches, and nosebleeds.  

This explains why high blood pressure is usually called the silent killer, as it increases the risk of stroke, heart attack, kidney damage, and blindness. As blood pressure levels increase, the higher the potential for damage. It’s crucial for people to consult a medical professional and have their blood pressure checked regularly.  

What causes hypertension?  

In most cases, the exact cause of high blood pressure is unknown, also called idiopathic. This is the most common type of blood pressure, also called essential or primary hypertension. Most American adults suffer from this form of blood pressure.  

The Centers for Disease Control and Prevention reports that more than half of the people above 50 years old suffer from hypertension. Women are just as likely as men to develop the condition, but there’s a difference in terms of the age when they could develop hypertension. Among people 45 years and below, it has been shown that more men are affected, while among people 65 years and up, more women are affected. It’s also interesting to note that African Americans have a higher chance of developing hypertension and at an earlier age compared to Americans of Hispanic or European descent.  

Although experts struggle to pinpoint the exact cause of hypertension, several factors have been identified to heighten the risk and exacerbate the problem. These include:  

  • Obesity  
  • Living a sedentary lifestyle – A severe lack of physical exercise  
  • Smoking cigarettes or tobacco products  
  • Drinking too much alcohol  
  • Adding too much sodium in daily eating regimen  
  • Using oral contraceptives or hormone therapy  
  • Using steroids, amphetamines, cocaine, and other drugs.  
  • Aging  
  • Acquiring hypertension when it runs in the family  

When high blood pressure is caused by at least one underlying health condition or the use of drugs, it’s referred to as secondary hypertension. This form of high blood pressure accounts for 5% of all cases. It’s imperative to identify the underlying condition that causes high blood pressure because its treatment can hold the key to normalizing the blood pressure level of the patient.  

Some examples of health conditions that lead to secondary hypertension include:  

  • Kidney disease or damage – Any form of kidney disease or damage can hamper the organ’s ability to get rid of salts and fluids from the body, inevitably causing a rise in blood volume and pressure. Because high blood pressure has also been shown to cause kidney damage, this can result in an endless cycle, thus requiring immediate treatment.  
  • Heart disease – A weak heart affects the contraction force and rate. This is another progressive problem that must be treated right away.  
  • Diabetes – This condition can lead to kidney damage and destroy the integrity of the blood vessels.  
  • Arteriosclerosis – This is a condition in which the arteries get unusually hard, making it difficult for them to dilate and constrict.  
  • Cushing syndrome – This disorder results in adrenal gland’s abnormal production of cortisol  
  • Hyperaldosteronism – Also called Conn syndrome, this condition involves the production of excessive aldosterone, a hormone that regulates the excretion and retention of sodium by the kidneys. In some cases, it’s caused by an adrenal gland tumor.  
  • Pheochromocytoma – This is a rare condition in which a tumor develops in the adrenal gland, usually benign. It causes an overproduction of epinephrine (adrenaline), which is produced by the adrenal glands to cope with stress. People suffering from pheochromocytoma usually deal with severe episodes of blood pressure.  
  • Thyroid disease – Blood pressure can be caused by both too much or too little production of thyroid hormone.  
  • Pregnancy – Pregnant women are susceptible to developing high blood pressure at any point during pregnancy, but most women experience it during the last trimester. At this time, it can lead to pre-eclampsia, which is characterized by heightened blood pressure and fluid retention.  

Laboratory tests for hypertension  

It’s important to understand that laboratory testing cannot diagnose hypertension conclusively, but these tests are done to identify conditions that can cause hypertension or make the problem worse. Tests are also necessary for evaluating organ function over time.  

Some of the general tests that may be necessary include:  

  • Urinalysis – This test aims to assess kidney function.  
  • Urinary albuminblood urea nitrogen, creatinine, and estimated glomerular filtration rate – These tests allow medical professionals to detect and monitor any kind of kidney dysfunction as well as evaluate the effects of medications on the kidneys.  
  • Potassium – This test is performed to evaluate electrolyte balance in the body. For instance, both Cushing syndrome and Conn syndrome can lead to low potassium, and these two are known to cause secondary hypertension. There are high blood pressure medications that upset the balance of electrolytes in the body, leading to the loss of potassium or its abnormal retention.  
  • Fasting glucose – This helps in diagnosing diabetes, which is linked to many hypertension cases. It also helps in monitoring glucose control.  
  • Calcium – This test determines the amount of calcium or ionized calcium in the blood. Overactive parathyroid glands, which lead to a boost in serum calcium, is linked to high blood pressure.  
  • Thyroid-stimulating hormone and T4 – This test is used to detect and evaluate thyroid dysfunction.  
  • Lipid profile – This test helps in the monitoring of total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides. It can also help identify the early signs of atherosclerosis.  
  • The basic metabolic panel usually includes a combination of the tests above, so patients may not have to undergo each individual test.  

Depending on the patient’s medical history, routine laboratory test results, and physical findings, additional non-routine tests may be necessary to help in identifying, diagnosing, and monitoring health conditions that cause secondary hypertension. These tests include:  

  • Aldosterone and renin – This test helps in detecting an overproduction of aldosterone or renin, both of which can cause kidney damage or the narrowing of the arteries.  
  • Cortisol and dexamethasone suppression test – This test helps in identifying excessive cortisol levels in the body, which can be caused by Cushing syndrome.  
  • Catecholamine and Metanephrines – This test is used to detect pheochromocytoma, which can lead to severe episodes of high blood pressure.