Published January 20th 2014
Thyroid hormone plays an important role in the entire body. After all, there are thyroid receptors in every cell, and so an increase or decrease in thyroid hormone can have a profound impact on many of the different systems of the body. The goal of this article will be to focus on how thyroid hormone affects the cardiovascular system, with a special emphasis on blood pressure. In addition, since I have spoken a great deal about the importance of the adrenals in other articles and blog posts, towards the end of this article I will discuss the importance of the adrenals in regulating blood pressure.
The Basics of Blood Pressure
Before I discuss the impact of thyroid hormone on blood pressure, I’d like to quickly explain what blood pressure is. Most people reading this know that the blood is carried from the heart to the different parts of the body through the arteries. The blood pressure represents the force of the blood that pushes against the walls of the arteries. Systolic blood pressure occurs when the heart beats, as during this time blood is pumped into the arteries. In a blood pressure reading the systolic blood pressure is the top number. On the other hand, diastolic pressure is the force of blood in the arteries as the heart relaxes between beats. In a blood pressure reading this is the bottom number. A blood pressure of less than 120/80 mmHg is considered to be normal, although many don’t consider it to be high until it reaches 140/90 mmHg.
The Prevalence of Hypertension
According to the American Heart Association, about 77.9 million adults have high blood pressure (1) . This means that about 1 out of every 3 people in the United States has this condition. Hypertension contributes to one out of every seven deaths in the United States, and approximately 70% of those who have a first heart attack or stroke or who have heart failure have hypertension (1) . And while medication can effectively help to manage hypertension in many cases, according to the statistics, 47.5 percent of people with high blood pressure do not have it controlled.
So it is very clear that hypertension is something to be taken very seriously. A big reason for the increased prevalence of hypertension relates to diet and lifestyle. Many people eat poorly and lead sedentary lives. Over 1.5 billion people worldwide are overweight or obese and over 40 million children under the age of 5 are overweight (2)  (3) . Obesity is a major risk factor for hypertension and cardiovascular disease. Speaking of obesity, if you haven’t read my article entitled “The Impact of Obesity on Thyroid Health ” then I recommend for you to do so when you get the chance.
How Does Thyroid Hormone Affect The Heart?
In hyperthyroidism, cardiac contractility is enhanced, and cardiac output, resting heart rate, and velocity of contraction and relaxation are increased (4) . The severity of the symptoms will of course affect people with hyperthyroid conditions differently. Some people will have a very high heart rate, sometimes exceeding 120 beats per minutes. Others might have a heart rate which is moderately high (i.e. between 100 and 120 beats per minute), while others will have a high pulse rate that is between 80 and 100 beats per minute. Heart palpitations are also common.
With hypothyroidism and Hashimoto’s Thyroiditis there is frequently the opposite effect. People with hypothyroid conditions will usually have a pulse rate on the low side. It’s not uncommon for people with Hashimoto’s Thyroiditis to experience heart palpitations, although they usually aren’t as severe as those experienced by people who have hyperthyroid conditions.
There is an interesting journal article written Dr. Sara Danzi and Dr. Irwin Klein, and in the article it is discussed how T3 is an important regulator of gene expression in the heart, and many of the cardiac manifestations of hyperthyroidism and hypothyroidism are associated with changes in T3-mediated cardiac gene expression (4) . This article also discussed how several important cardiac gene products play a role in regulating cardiac contractility, and that T3 is important when it comes to muscle contraction. The same article also discusses how thyroid hormone is important in coordinating the electrochemical and mechanical responses of the myocardium.
Hypertension and Hyperthyroidism. Many people with hyperthyroidism and Graves’ Disease have high blood pressure. However, not everyone who has a hyperthyroid condition has high blood pressure. There are some people who have a high pulse rate and palpitations, yet have a normal blood pressure. This actually described me when I was diagnosed with Graves’ Disease, as while I had a high pulse rate and palpitations, my blood pressure was normal.
Hypertension and Hypothyroidism. One might expect people with hypothyroid conditions to have low blood pressure. And while sometimes this is the case, an elevated blood pressure is a common finding in patients with overt hypothyroidism (5) . But why would people with hypothyroidism experience an increase in blood pressure? The first reason is the increase in peripheral vascular resistance (6) . The second reason is due to an increase in arterial stiffness, which is most likely due to myxedema of the arterial wall (7) .
The good news is that regulation of blood pressure usually improves once the thyroid hormone levels are in balance. In other words, when the person reaches a state of euthyroidism then the high blood pressure will typically become normal. This is the case with both hyperthyroid and hypothyroid conditions. However, there of course can be other factors which lead to high blood pressure, and if this is the case then balancing the thyroid hormone levels might not lead to a lowering of blood pressure in people with hypertension.
The Role Of The Adrenals In Regulating Blood Pressure
In addition to the importance of thyroid hormone in blood pressure regulation, the adrenals also play an important role. I have discussed the importance of the adrenals in other articles, but I usually focus on the hormone cortisol, and sometimes DHEA. But aldosterone is another hormone secreted by the adrenals, and it helps with the regulation of blood pressure.
Aldosterone increases the absorption of sodium and water and causes the excretion of potassium in the kidneys, which in turn raises blood pressure (8) . Because aldosterone results in the excretion of potassium, too much aldosterone can lead to hypokalemia (low potassium levels). This can lead to severe muscle weakness, as well as high blood pressure. On the other hand, a deficiency of aldosterone can lead to hyperkalemia (high potassium), which can cause serious cardiac problems, and even lead to death if not addressed.
There can be numerous reasons for high aldosterone levels, including an adrenal tumor, low sodium and/or high potassium levels, and it can also be the result of secondary hyperaldosteronism from heart or kidney disease (9) . On the other hand, if someone has low levels of aldosterone this can be due to adrenal fatigue, or a severe condition such as Addison’s disease. In some cases a very high-sodium diet can also lead to low levels of aldosterone.
Tips To Lowering High Blood Pressure
So how can one effectively lower high blood pressure? To no surprise, conventional medicine usually uses medication for moderate to severe cases of high blood pressure. And to be fair, in some cases it is a good idea to take this medication to manage the symptoms. However, the goal shouldn’t be to take these prescription drugs for a prolonged period of time, but instead should be to address the actual cause of the condition. I’m not going to get into too much detail about managing blood pressure, but here are a few things which can help many people
1. Eat a healthy diet. This goes without saying, as eating well is important when dealing with any chronic health condition.
2. Exercise regularly. Numerous studies have shown that exercise can help to reduce blood pressure (10)  (11) . One study I came across even showed that aerobic exercise can reduce blood pressure in resistant hypertension (12) , which is high blood pressure in people taking antihypertensive medication.
3. Manage your stress levels. Stress can cause hypertension through repeated blood pressure elevations as well as by stimulation of the nervous system to produce large amounts of vasoconstricting hormones that increase blood pressure (13) . This is yet another reason to attempt to reduce your stress levels, and at the same time improve your stress handling skills.
4. Optimize thyroid and adrenal health.> This article discussed the role of thyroid hormone in blood pressure regulation, and also how the adrenals play an important role in blood pressure regulation. And so having normal thyroid hormone levels is important in regulating blood pressure. And having healthy adrenal glands is also essential.
5. Consider nutritional supplementation for high blood pressure. Certain supplements have been shown to lower blood pressure. There is evidence that fish oils and CoQ10 can lower blood pressure. Certain herbs such as Hawthorn might also be able to lower blood pressure. One study I came across concluded that CoQ10 has the potential in hypertensive patients to lower systolic blood pressure by up to 17 mm Hg and diastolic blood pressure by up to 10 mm Hg without significant side effects (14) . With regards to fish oils, there is evidence that high intake of fish oils may lower blood pressure, especially in older and hypertensive subjects (15) . There are other studies which also show that CoQ10 and fish oils might benefit people with hypertension (16)  (17) . There is evidence that garlic can lower blood pressure (18) . I came across a study which showed that green tea consumption can have a positive influence on blood pressure, along with insulin resistance, inflammation, oxidative stress, and the lipid profile in patients with obesity-related hypertension (19) .
In summary, thyroid hormone has a profound effect on the cardiovascular system, and can also affect blood pressure. Many people with both hypothyroid and hyperthyroid conditions have hypertension. And while balancing the thyroid hormone levels will frequently help to regulate the blood pressure, sometimes this isn’t the case. Other factors might need to be addressed, such as compromised adrenals. In addition, eating well, exercising regularly, managing one’s stress, and taking certain supplements can all help to lower blood pressure in hypertensive individuals.