Blog # 19- The Cardiovascular Endocrine Connection: The Correlation Between Thyroid Hormone and the Heart

Resources used in this blog:

“Thyroid hormone: How it affects your heart” Harvard Medical School. Retrieved from https://www.health.harvard.edu/heart-health/thyroid-hormone-how-it-affects-your-heart. Published Feb. 2015.

         What we all need to realize is that the thyroid is a major organ along the thyroid cartilage and the trachea which helps promote metabolism. A regulating metabolism is essential for all functions of the body. Thyroid hormone is essential to regulating a healthy heart. Thyroid hormone has several functions when it comes to the heart: 1.) Thyroid hormone influences the contractions of the blood flow through blood vessels that support the human body; 2.) The amount of thyroid hormone you have determines the speed and force of your heartbeats; and 3.) The amount of thyroid hormone you have also determines how much cholesterol you have. The reality is that, “a malfunctioning thyroid gland can cause problems that masquerade as heart disease or make heart disease worse” (Harvard Medical School, 2015).

         What can happen to the heart when people have hypothyroidism? People with high amounts of thyroid stimulating hormone (TSH) and low amounts of thyroxine (T4), this being the least metabolically active form of thyroid hormone, and low amounts of triiodothyronine (T3), this being the most metabolically active form of thyroid hormone, are those with hypothyroidism. Some people, however, may only have high amounts of TSH (thyroid stimulating hormone) and normal T4 (thyroxine) and normal T3 (triiodothyronine) amounts, which they would be known to have subclinical hypothyroidism. Regardless, people with hypothyroidism can have bradycardia, also known as a slow heart rate of less than 60 beats a minute. In addition, because of a slow heart rate, eventually, the arteries get thicker and they harden, and as a result, blood cannot properly circulate into the blood vessels to be transported to all the organs in the body. Hypertension can result as the heart tries to circulate blood throughout the body. With this said, however, people become at risk for myocardial infarctions (also known as heart attacks). Most people with hypothyroidism are on levothyroxine (a T4 medication), or Cytomel (a T3 medication), a combination of both medications, or on natural desiccated thyroid medication. Again, regardless, when people start experiencing hypothyroid symptoms, including a slow heart rate, it is very important to follow up with their primary care providers to have their levels checked to see whether the dosage of their medications need to be adjusted to bring thyroid hormone levels back into the proper therapeutic ranges.

         Now, here is what can happen to the heart for people with hyperthyroidism? When people have low TSH (thyroid stimulating hormone) levels, and high T4 (thyroxine) and high T3 (triiodothyronine), they have hyperthyroidism. Again, similar to people with subclinical hypothyroidism, you could still have normal T4 and T3 levels, however, the difference is the TSH level where for hyperthyroidism it is low, so people would have what is called subclinical hyperthyroidism. In people with hyperthyroidism, “Excess thyroid hormone also causes the heart to beat harder and faster and may trigger abnormal heart rhythms” (Harvard Medical School, 2015). People with hyperthyroidism may experience what is called tachycardia, which are heartbeats above 100 beats per minute. People with hyperthyroidism are at risk of atrial fibrillation, which is when irregular heartbeats promote rapid pulses which result in poor blood flow to the vessels and the organs in the human body. Palpitations are also common in people with hyperthyroidism, and that is when the heart may be beating too fast, pumping too much blood, and causing a fluttering sensation. Hypertension is also common in people with hyperthyroidism just like in people with hypothyroidism. Another key point is that, “In a person with clogged, stiff heart arteries, the combination of a forceful heartbeat and elevated blood pressure may lead to chest pain or angina” (Harvard Medical School, 2015). People with hyperthyroidism will generally take antithyroid medications such as Methimazole or Propylthiouracil (PTU) to regulate thyroid levels back into the therapeutic ranges and to alleviate symptoms of hyperthyroidism, especially symptoms in relation to the heart. When people experience hyperthyroid symptoms even when on an antithyroid medication, they need to let their doctors know to have their levels checked to see if more medication is needed. Radioactive iodine therapy and surgery may also benefit as well. Beta blockers such as Atenolol and Propranolol to help treat palpitations; tremors; and hypertension for people with hyperthyroidism.

         The reality is that when you have a malfunctioning thyroid, whether due to too little thyroid hormone (hypothyroidism), or too much thyroid hormone (hyperthyroidism), you are at risk of developing heart issues whether that be atherosclerosis; hypertension; myocardial infarctions; atrial fibrillations; palpitations; or even angina (or chest pain). Being aware of your symptoms, and following up with your doctor, or even your endocrinologist, is key to evaluating, and, if necessary, treating the symptoms to prevent the likelihood of cardiovascular disease. Be mindful of your medications, and if you feel you are getting too much or too little in terms of dosages, let your doctor or endocrinologist know. You want to be able to regulate proper amounts of thyroid hormone so your heart can regulate properly.

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