From the Guidelines
A thyroid mass can cause tachycardia when it produces excess thyroid hormones, leading to hyperthyroidism, which is a condition that increases the body's metabolic rate and directly affects the heart by increasing both heart rate and contractility, resulting in tachycardia (heart rate above 100 beats per minute) 1. This commonly occurs with toxic nodular goiters or in Graves' disease where antibodies stimulate the thyroid to overproduce hormones. The excess thyroid hormones increase the body's metabolic rate and directly affect the heart by increasing both heart rate and contractility, resulting in tachycardia. Other symptoms that may accompany the tachycardia include:
- Palpitations
- Anxiety
- Weight loss despite increased appetite
- Heat intolerance
- Tremors Diagnosis typically involves blood tests measuring thyroid hormone levels (TSH, T3, T4) and imaging studies like ultrasound to evaluate the mass.
Treatment Options
Treatment depends on the underlying cause but may include:
- Anti-thyroid medications (methimazole or propylthiourol)
- Beta-blockers (propranolol) to control heart rate symptoms, as recommended by the American Association of Clinical Endocrinologists Medical Guidelines for the Evaluation and Treatment of Hyperthyroidism and Hypothyroidism 1
- Radioactive iodine therapy
- Surgical removal of part or all of the thyroid gland The tachycardia typically resolves once the hyperthyroidism is effectively treated. According to the American Heart Association, the initial treatment of patients with cardiac-related symptoms and signs of hyperthyroidism should include a β-blocker to lower the heart rate to nearly normal 1.
From the Research
Thyroid Mass and Tachycardia
- The relationship between thyroid mass and tachycardia is often associated with hyperthyroidism, a condition where the thyroid gland produces excess thyroid hormones 2.
- A study published in 2022 found that tachycardia, defined as a heart rate greater than 100 bpm, was present in 28.2% of patients with hyperthyroidism 2.
- The same study found that tachycardia was associated with higher levels of free thyroxine (fT4) and diastolic blood pressure, suggesting a possible link between thyroid hormone levels and heart rate 2.
Prevalence of Tachycardia in Hyperthyroidism
- The study found that tachycardia was not as common as previously thought, with only 28.2% of patients exhibiting a heart rate greater than 100 bpm 2.
- A more lenient definition of tachycardia, with a heart rate greater than 90 bpm, was seen in 47.2% of patients, suggesting that some degree of tachycardia may be more common than previously thought 2.
- The study suggests that the relatively infrequent finding of tachycardia may be due to differences in medical practice, including the increased ordering of thyroid function tests, which may uncover cases of mild or asymptomatic thyrotoxicosis 2.