Why Do Hypothyroid Patients Experience Heart Palpitations?
Hypothyroidism, commonly known as an underactive thyroid, occurs when the thyroid gland fails to produce and secrete sufficient levels of thyroid hormones. This hormonal imbalance leads to a slowdown in the body's metabolic processes, resulting in a range of symptoms such as chronic fatigue, increased sensitivity to cold, reduced or absent sweating, unexplained weight gain, and facial or eyelid swelling. These are classic signs of low metabolism associated with hypothyroidism.
Understanding the Paradox: Heart Palpitations in a Low-Metabolism State
Typically, hypothyroid patients exhibit a slower-than-normal heart rate due to decreased metabolic activity. Therefore, the occurrence of heart palpitations—often described as a racing, fluttering, or pounding sensation in the chest—can seem contradictory. However, several underlying conditions may explain this phenomenon, and it's crucial for patients and healthcare providers to investigate further when such symptoms arise.
1. Presence of Arrhythmias
One potential cause of palpitations in hypothyroid individuals is the development of cardiac arrhythmias. Even with low thyroid hormone levels, abnormal heart rhythms can occur. When experiencing palpitations, patients should undergo an electrocardiogram (ECG) during the episode to assess the heart's electrical activity. Conditions like atrial fibrillation or other rhythm disturbances may coexist with hypothyroidism and require specific treatment.
2. Overreplacement with Thyroid Hormone Medication
Most hypothyroid patients are treated with levothyroxine sodium, a synthetic form of thyroid hormone used to restore normal hormone levels. However, if the prescribed dose exceeds what the body needs, it can lead to a condition known as iatrogenic hyperthyroidism—or drug-induced overactive thyroid. In such cases, patients may experience symptoms typical of hyperthyroidism, including rapid heartbeat, anxiety, tremors, and palpitations. Regular monitoring of thyroid function tests (TSH, T3, T4) is essential to ensure optimal dosing and avoid hormonal imbalances.
3. Coexisting Cardiovascular Conditions
Hypothyroidism is often linked with elevated cholesterol levels and an increased risk of cardiovascular disease. Some patients may also have undiagnosed coronary artery disease or angina. When these conditions are present, episodes of chest tightness, shortness of breath, and palpitations can occur—even in the context of an otherwise slow metabolism. It's important not to dismiss palpitations as unrelated to the thyroid; instead, a comprehensive cardiac evaluation should be considered, especially in older adults or those with risk factors like hypertension, diabetes, or a family history of heart disease.
When to Seek Medical Attention
Persistent or worsening palpitations should never be ignored, even in individuals being treated for hypothyroidism. Sudden onset of rapid heartbeat, dizziness, fainting, or chest pain warrants immediate medical assessment. Early diagnosis and appropriate management can prevent complications such as heart failure or stroke, particularly in long-standing or poorly controlled cases.
Preventive Strategies and Ongoing Care
Maintaining stable thyroid function through consistent medication use, routine blood testing, and lifestyle modifications—including a heart-healthy diet, regular physical activity, and stress reduction—can significantly reduce the risk of palpitations. Patients should work closely with their endocrinologist or primary care provider to tailor treatment plans that address both thyroid health and overall cardiovascular wellness.