Heart palpitations are the awareness of an abnormal heartbeat, often felt as a racing, pounding, or skipped sensation. While external factors like stress or caffeine can trigger them, the body’s endocrine system plays a significant role in cardiovascular function. Hormones act as chemical messengers that influence the heart’s rate and rhythm.
How Hormones Influence Heart Rhythm
Hormones directly affect the heart’s electrical conduction system. They modulate how quickly or slowly the sinoatrial (SA) node, the heart’s natural pacemaker, sends electrical signals. Sex and thyroid hormones can modify ion channels that regulate electrical activity within heart muscle cells.
The sympathetic nervous system is responsible for the “fight or flight” response, increasing heart rate and contractility. Hormones like adrenaline and cortisol modulate this system. An increase in these hormones creates heightened cardiac excitability, which can trigger temporary changes in heart rhythm perceived as palpitations.
Thyroid Hormones: A Major Endocrine Culprit
Thyroid hormones have a profound and direct effect on the heart and circulatory system. Excess thyroid hormone, known as hyperthyroidism, significantly increases the body’s metabolic rate. This overactivity leads to increased resting heart rate and contractility, often causing palpitations and sustained rapid heart rate (tachycardia).
The enhanced sympathetic activity is partially attributed to elevated thyroid hormone levels, which increase the sensitivity of the heart’s beta-adrenergic receptors. This makes the heart more responsive to the body’s natural adrenaline-like signals, which can lead to rhythm disturbances like atrial fibrillation.
While hyperthyroidism is a common cause of palpitations, hypothyroidism (too little thyroid hormone) can also affect the heart. Low thyroid levels typically reduce heart rate and cardiac output, but they are associated with other cardiovascular issues, such as fluid retention or impaired contractility. Evaluating thyroid function is a standard step in diagnosing the cause of persistent palpitations due to this strong endocrine-cardiac link.
Sex Hormone Fluctuations and Palpitations
Fluctuations in the sex hormones estrogen and progesterone are among the most frequent hormonal causes of palpitations, particularly in women. These hormones affect the heart’s electrical signaling pathways, and their changing levels can overstimulate the heart in sensitive individuals.
During the menstrual cycle, women may experience palpitations during specific phases when estrogen and progesterone levels naturally rise and fall. These changes can affect the heart’s electrical activity, sometimes triggering palpitations right before or during the monthly period. Progesterone is thought to have a calming effect and helps regulate mediators of the stress response, which may explain why low progesterone periods can be associated with increased cardiac awareness.
The transition into perimenopause and menopause, characterized by declining and fluctuating estrogen levels, is a time when up to 50% of women report experiencing palpitations. Estrogen typically offers a protective effect on the cardiovascular system, and its decline can lead to an increase in sympathetic nervous system outflow, causing irregular or pounding heartbeats.
Pregnancy involves dramatic hormonal surges, combined with a significant increase in blood volume, which forces the heart to work harder. The resulting increase in cardiac workload and hormonal shifts can lead to palpitations in many pregnant women. While these palpitations are often considered harmless, any heart rhythm changes during pregnancy still warrant medical monitoring.
When Palpitations Require Medical Evaluation
While many hormone-related heart palpitations are benign, medical evaluation is important to rule out serious underlying cardiac conditions. Certain accompanying symptoms, known as red flags, necessitate urgent medical attention. These warning signs include chest pain or discomfort, shortness of breath, significant dizziness, or fainting (syncope).
The diagnostic process typically begins with a standard 12-lead electrocardiogram (ECG) to assess the heart’s electrical activity. Since palpitations are often intermittent, a doctor may recommend a Holter monitor, a portable ECG device that records the heart’s rhythm over 24 to 48 hours or longer. Blood tests are also routinely performed to check for hormonal imbalances, particularly thyroid hormone levels, to identify a treatable endocrine cause.