The thyroid gland, a small, butterfly-shaped organ located at the front of your neck, regulates the body’s metabolism. It produces hormones, thyroxine (T4) and triiodothyronine (T3), which convert food into energy and influence nearly every cell and organ system. These hormones help control various bodily functions, including breathing, digestion, body temperature, and brain development.
The Thyroid-Heart Connection
Thyroid hormones significantly influence the cardiovascular system by directly affecting heart cells and blood vessels. These hormones help regulate heart rate, the strength of heart contractions, and the amount of blood pumped with each beat (cardiac output). They also control blood pressure and systemic vascular resistance, which is the resistance the heart encounters when pumping blood through the body.
Thyroid hormones achieve these effects through complex mechanisms, influencing gene expression within heart cells and altering the sensitivity of cardiac tissues to other stimulating hormones. This regulation means minor changes in thyroid hormone levels can lead to noticeable changes in heart function.
Impact of Overactive Thyroid on the Heart
An overactive thyroid, known as hyperthyroidism, occurs when the thyroid gland produces excessive thyroid hormones. This surplus speeds up the body’s metabolism, affecting the cardiovascular system. The heart often responds with an increased resting heart rate, tachycardia, which can exceed 100 beats per minute.
Excess thyroid hormones can make the heart more sensitive to stimulating signals, leading to palpitations. Atrial fibrillation (AFib), where the upper chambers of the heart beat irregularly, is a common heart rhythm disorder associated with hyperthyroidism. This irregular rhythm can reduce the heart’s pumping efficiency and increase stroke risk. Prolonged hyperthyroidism can also lead to an increased workload on the heart, potentially resulting in heart failure, where the heart cannot pump enough blood to meet the body’s needs. The increased metabolic activity and dilated blood vessels contribute to a hyperdynamic circulatory state, characterized by increased cardiac output and sometimes elevated systolic blood pressure.
Impact of Underactive Thyroid on the Heart
An underactive thyroid, or hypothyroidism, results from insufficient thyroid hormone production. This deficiency slows the body’s metabolic processes, affecting the heart. A common cardiovascular manifestation of hypothyroidism is a slowed heart rate, known as bradycardia.
Hypothyroidism can lead to increased systemic vascular resistance, meaning blood vessels become stiffer and narrower, making it harder for the heart to pump blood. This increased resistance often results in elevated blood pressure, particularly diastolic hypertension. Insufficient thyroid hormones can also negatively impact the heart’s ability to contract and relax efficiently, leading to decreased cardiac output. Hypothyroidism is associated with elevated cholesterol levels, which can contribute to atherosclerosis, where plaque builds up in the arteries. In some cases, fluid can accumulate around the heart in the pericardial sac, pericardial effusion, though it often develops slowly.
Recognizing Symptoms and Seeking Care
Recognizing symptoms of a thyroid-related heart issue is important for seeking medical care. Symptoms of an overactive thyroid include a rapid heart rate, palpitations, nervousness, unexplained weight loss, and sensitivity to heat. Signs of an underactive thyroid often involve a slower heart rate, persistent tiredness, unexplained weight gain, feeling cold more than usual, and changes in blood pressure.
Consult a healthcare professional if you experience any of these symptoms. A doctor can assess your condition through a physical exam and blood tests that measure thyroid hormone levels, such as thyroid-stimulating hormone (TSH), T4, and T3. These tests help determine if your thyroid is functioning properly and guide management. Early diagnosis and care are important for managing thyroid conditions and preventing heart complications.