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The thyroid hormone has an effect on every organ system in the body. And in fact, the thyroid plays a crucial role in helping regulate some of our most vital functions, including heart rate, body temperature, and blood pressure. Therefore, it should be no surprise that when thyroid hormone levels are off, the entire body, and its most important functions, may be compromised. For this reason, people with an underactive thyroid often have symptoms that can affect the whole body. Here, we focus on high blood pressure and how an underactive thyroid influences this vital function.
Hypothyroidism is one of the most common thyroid problems affecting people in the United States. According to the American Thyroid Association, more than 12% of the population will have a thyroid condition at some point during their lives. Over half of these individuals are unaware that they have a thyroid problem.
Hypothyroidism is when the thyroid gland does not produce enough thyroid hormone. There are several reasons this problem may develop, but one of the most common causes in the U.S. is an autoimmune condition called Hashimoto's thyroiditis. Globally, the primary cause of hypothyroidism is a lack of dietary iodine, which is necessary to make thyroid hormones. Iodine deficiency, however, is becoming less of a factor, as iodized salt is available in most places.
When thyroid hormones are too low in the body, every system can be thrown off. Because thyroid hormones help regulate metabolism, having a medical condition such as hypothyroidism can cause organ systems to slow down, weight gain, and more. Some symptoms of hypothyroidism include fatigue, constipation, muscle pains, dry skin, slowed heart rate, and cold intolerance.
Primary hypertension (the medical term for high blood pressure) is a common problem among people with thyroid disorders, including hypothyroidism. High blood pressure caused by hypothyroidism is a form of secondary hypertension. Secondary hypertension is high blood pressure caused by other health conditions, such as kidney disease, heart disease, and diabetes.
Hypothyroidism can cause high blood pressure in certain individuals for reasons still not clear. There does seem to be a genetic component to mutations in the coding for thyroid hormone signaling, transporters, and receptors. Indeed, even small changes in thyroid hormone levels can increase one risk for cardiovascular problems, among other complications, including bone mineral density. As one study suggest, each person has a unique thyroid set point that is affected by genetic and environmental factors.
Research also shows that thyroid hormone affects the mechanisms behind lipid homeostasis. Indeed, hypothyroidism is one of the more common secondary causes of dyslipidemia and, subsequently, atherosclerotic cardiovascular disease. When thyroid hormone levels are low, it can cause dyslipidemia, where total cholesterol and low-density lipoprotein (LDL) cholesterol levels are elevated. High cholesterol can lead to atherosclerosis, a condition where lipids accumulate in the blood vessels, which restricts the ability of blood to flow smoothly and without added pressure. Additionally, thyroid hormone may affect coagulation parameters as well, causing more vascular resistance.
Furthermore, studies show that normal to high-normal elevated TSH levels over an 11-year study period resulted in a moderate increase in high blood pressure.
While we know that hypothyroidism can be a secondary cause of cardiovascular problems, there is still much more research necessary to uncover the exact relationship between thyroid hormones and the biochemical and molecular mechanisms of blood pressure.
Blood pressure comprises two numbers: the first (or top) number represents your systolic pressure, and the second (or bottom) number represents your diastolic pressure. Systolic blood pressure is the pressure exerted on your vessels when the heart muscles forcefully pump blood. Diastolic blood pressure is the pressure exerted when your heart is filling with blood and resting. As you can imagine, your systolic number will always be higher than your diastolic.
The "classic" blood pressure number is 120/80. But according to most sources, including the Centers for Disease Control and Prevention, 120/80 is the lowest number for people at risk for hypertension or prehypertension. The range for blood pressure is as follows:
Normal range = systolic <120 mm Hg and diastolic < 80 mm Hg
Prehypertension = systolic between 120-139 mm Hg and diastolic between 80-89 mm Hg
Hypertension = systolic 140 mm Hg or higher and diastolic 90 mm Hg or higher
When it comes to treating secondary hypertension, the good news is that you can usually treat high blood pressure by treating the condition causing it. In the case of hypothyroidism, you may be able to improve blood pressure by taking thyroid hormone replacement medication. Additionally, lifestyle changes meant to improve your thyroid health may also lead to better blood pressure readings (think diet, exercise, stress management, and better sleep).
If you have high blood pressure, it will be important to monitor your blood pressure based on your doctor's recommendations. Tracking is especially important for instances where you are managing your thyroid and blood pressure medication if you have been prescribed for hypertension. Your doctor may treat your hypothyroidism before giving you medication for blood pressure, as thyroid hormone therapy may be just what you need to normalize blood pressure levels.
To find out if hypothyroidism is behind high blood pressure readings, take an at-home thyroid test to get an idea of your thyroid function. Even subclinical thyroid dysfunction can affect blood pressure, so always consider your thyroid health when dealing with hypertension.
It’s important to recognize that lifestyle changes are crucial for maintaining healthy blood pressure, especially for conditions such as hypothyroidism.
Your primary care physician will be the one to establish the cadence at which you should test. We also recommend reducing inflammation through food and lifestyle changes. Schedule a visit with a Paloma nutritionist today to see how you can optimize your health through whole-based food.