The thyroid is a gland in the neck that is responsible for producing the thyroid hormone. This hormone circulates throughout the body and has many effects. The level of thyroid hormone within the body is strictly regulated to modulate and control its effects. Patients with an excessive or deficient amount of thyroid hormone will likely experience adverse conditions and symptoms. The thyroid hormone can affect the cardiovascular system, and an understanding of these effects can help physicians comprehend the importance of the hormone.
Increased Heart Rate
Thyroid hormone can cause the heart rate to increase, according to the Journal of Clinical Endocrinology and Metabolism in the article, "Effects of thyroid hormone on cardiac function." Specialized cells in the heart typically control how fast the heart beats. However, when thyroid hormone interacts with the heart cells, the heart rate drastically increases. As heart rate increases, the amount of blood pumped to the rest of the body increases. However if the heart beats too quickly, the patient may experience atrial fibrillation, which is a serious condition of irregular heartbeat.
Vasodilation
Vasodilation is the physiologic process of increasing the diameter of blood vessels. Thyroid hormone can cause vasodilation, states the Hypertexts for Biomedical Sciences website produced by Colorado State University. This vasodilation allows for increased blood flow to many of the organs within the body in response to an organ's demand for oxygen. Increased blood flow means that the organs are receiving more oxygen and nutrients.
Increased Contractility
Contractility refers to the heart's ability to forcefully pump blood. Increased contractility means that the strength of the heart muscles has increased, and therefore the force at which the heart beats is increased. A heart that has a high level of contractility can more efficiently send blood to the rest of the body. Increased contractility is one of the effects associated with thyroid hormone, reports the Journal of Clinical Endocrinology and Metabolism.
Cellular Hypertrophy
The thyroid hormone has been reported to cause cellular hypertrophy within the heart, according to the Journal of Endocrinology in the article "Thyroid hormone inhibits proliferation of fetal cardiac myocytes in vitro." Cellular hypertrophy is defined as the increase in size of cells. In the context of the heart, cellular hypertrophy refers to the increase in size of cardiac muscle cells. As the cells increase in size, they increase in power, which allows the heart to beat more forcefully. However, cells that become too large begin to decrease the volume of the chambers of the heart, which can hinder the heart's ability to send blood to the other organs of the body.
References
- "Journal of Endocrinology"; Thyroid hormone inhibits proliferation of fetal cardiac myocytes in vitro; 2007
- Colorado State University: Mechanism of Action and Physiologic Effects of Thyroid Hormones
- "Journal of Clinical Endocrinology and Metabolism"; Effects of Thyroid Hormone on Cardiac Function.; 2002
