The answer is yes! Thyroid disorders (both hypo- and hyperthyroid) have profound cardiovascular effects. In this article, let’s see how hyperthyroidism can affect the cardiovascular system and how to manage it.
What is Hyperthyroidism?
Hyperthyroidism, also known as overactive thyroid, is a condition in which the thyroid gland produces more thyroid hormones than the body needs. These hormones-thyroxine (T4) and triiodothyronine (T3)-regulate the body’s metabolism, so their excess accelerates many bodily functions.
Common symptoms include weight loss despite increased appetite, rapid or irregular heartbeat, nervousness, irritability, tremors, excessive sweating, heat intolerance, muscle weakness, and an enlarged thyroid gland (goitre).
The causes of hyperthyroidism are autoimmune disease(Graves’ disease), inflammation(thyroiditis), thyroid tumours (toxic nodules), excessive iodine intake and medication overdose, etc.
Signs of Cardiac Involvement in Hyperthyroidism
Symptoms
- Palpitations are the most common early symptom, reported in up to 80% of hyperthyroid patients.
- Breathlessness (dyspnea) and exercise intolerance are frequently noted.
- Chest pain, often angina-like, can occur, especially in those with underlying coronary artery disease.
Signs
- Sinus tachycardia (resting heart rate >100 bpm) is the most prevalent early sign, present in 70–80% of cases.
- Systolic hypertension and widened pulse pressure may be observed in around one-third of patients.
- Atrial fibrillation can develop, especially in older adults, with a prevalence of 10–20%. Hyperthyroidism causes atrial fibrillation (AF) through multiple interrelated mechanisms involving direct effects of thyroid hormones on the heart and indirect effects on the autonomic nervous system and hemodynamics:
- Hyperthyroidism increases cardiac output (50–300%) via reduced vascular resistance and elevated heart rate/contractility. Therefore, causing high-output heart failure and pulmonary oedema.
- ECG may reveal sinus tachycardia as the most common abnormality, followed by atrial fibrillation and, less frequently, left ventricular hypertrophy or other conduction changes.
Diagnostic tests for Hyperthyroidism
- Labs: Confirm elevated thyroid hormone levels (Free T4/Free T3), suppressed TSH; assess hypercalcemia, hyperglycemia, and liver enzymes.
- Cardiac assessment: ECG for arrhythmias (e.g., atrial fibrillation), chest X-ray for heart failure, and monitoring for tachycardia (>130 bpm).
- NT-proBNP/BNP: Elevated in heart failure.
- TSH-receptor antibodies (TRAb): In Graves’ disease.
Treatment
Hospitalisation is required in case of hyperthyroidism with heart failure
- Management
- Restore Euthyroidism (normalise the thyroid hormone)
- Antithyroid drugs (e.g., Methimazole, PTU)
- Radioiodine therapy
- Thyroidectomy (in select cases)
- Cardiovascular Support
- Beta-blockers (Propranolol, Atenolol): First-line to control symptoms.
- Anticoagulation: In AF, based on stroke risk.
- Diuretics: For symptomatic heart failure.
- ACE inhibitors/ARBs: For LV dysfunction or hypertension.
- Rate or Rhythm Control in case of atrial fibrillation.
- Restore Euthyroidism (normalise the thyroid hormone)
Prognosis and Reversibility
Most cardiac changes are reversible with timely treatment of hyperthyroidism. Persistent AF or structural heart disease may require long-term cardiovascular therapy. Delayed diagnosis may lead to irreversible cardiomyopathy.
Conclusion:
Hyperthyroidism is a systemic condition with profound cardiovascular effects. Clinicians should maintain a high index of suspicion for thyroid dysfunction in patients with new-onset atrial fibrillation, high-output heart failure, or unexplained tachyarrhythmias. Early diagnosis and appropriate therapy can reverse most cardiac manifestations and significantly improve patient outcomes.
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