Some research suggests there may be a link between hyperthyroidism and tachycardia. When a person has hyperthyroidism, the body produces too much thyroid hormone, which can affect the heart.

People may also refer to hyperthyroidism as an overactive thyroid. This condition can cause several bodily functions to speed up, including the heartbeat.

Tachycardia is the medical term for a fast heart rate of more than 100 beats per minute when a person is at rest. A fast heart rate can lead to a shortage of blood flow to the rest of the body.

This article explores whether there is a link between hyperthyroidism and tachycardia, alongside causes of hyperthyroidism, how a doctor may diagnose the condition, and treatment options. It also discusses when someone should consider visiting a healthcare professional.

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According to 2019 research, thyroid hormones have a direct effect on the cardiovascular system and can affect the typical function of the heart.

When a person has hyperthyroidism, the body produces too much thyroid hormone. This can cause an increased heart rate and an increase in the amount of blood the heart pumps with each beat. This can strain the heart and affect how well it can respond to the rise in thyroid hormone.

A 2022 research review suggests that excess thyroid hormones can lead to arrhythmias (irregularities with the heartbeat), including tachycardia.

However, other 2022 research suggests that, despite older studies suggesting the contrary, it may be less common for a person with hyperthyroidism to experience tachycardia. This may be due to healthcare professionals recommending thyroid function tests more often than before, which can help diagnose mild or asymptomatic thyrotoxicosis.

There are several reasons a person may develop hyperthyroidism. Some of these can include:

  • Graves’ disease: This condition is the most common cause of hyperthyroidism. Graves’ disease is a condition in which the immune system mistakenly attacks the thyroid. This can cause the thyroid to produce too much thyroid hormone.
  • Thyroiditis: This is inflammation of the thyroid gland, which can cause thyroid hormone to seep into the bloodstream.
  • Overactive thyroid nodules: A thyroid nodule describes an atypical growth of cells in the thyroid. These can become overactive and produce too much thyroid hormone.
  • Certain medications: For example, taking too much thyroid hormone medication for hypothyroidism can cause thyroid hormone levels to rise to high levels. A doctor can adjust a person’s dosage if they notice this happening.
  • A noncancerous tumor: If a person develops a noncancerous tumor of the pituitary gland at the bottom of the brain, they may develop hyperthyroidism. However, this is rare.
  • Iodine: The thyroid gland uses iodine to produce thyroid hormone. If a person consumes too much iodine, the thyroid gland may produce too much thyroid hormone. Certain medications, cough syrups, seaweed, and seaweed products may contain large amounts of iodine.

Hyperthyroidism typically shares symptoms with several other health conditions. Therefore, to diagnose hyperthyroidism, a doctor will typically perform a physical exam and order thyroid blood tests, such as tests to measure T3 and T4 levels.

A doctor may also schedule several imaging scans to help diagnose hyperthyroidism. These can include:

  • Thyroid ultrasound: Doctors use this imaging scan to identify thyroid nodules and determine whether they may be cancerous. A thyroid ultrasound is safe, painless, and usually takes around 30 minutes. It involves a healthcare professional running a transducer over a person’s neck while they lie on an examination table. A transducer uses sound waves to produce images of the inside of the body.
  • Thyroid scan: A person will typically ingest a small amount of radioactive iodine through injection or in capsule form. Approximately 30 minutes after injection or up to 24 hours after swallowing the iodine, a doctor will use a special camera to scan and capture images of the thyroid gland while a person lies on an examination table. It typically takes 30 minutes or less.
  • Radioactive or thyroid uptake test: A person will typically swallow a small amount of radioactive iodine in liquid or capsule form. A doctor will then use a device known as a gamma probe to measure how much iodine the blood absorbs. If the blood absorbs a large amount of iodine, this can be a sign of hyperthyroidism.

To diagnose tachycardia, a doctor may take several blood tests. They may also perform an electrocardiogram, which measures electrical changes in the heart.

The main goal of treatment for hyperthyroidism is to slow down the production of thyroid hormone.

A doctor will typically prescribe medication, such as thiamazole or carbimazole, as a first-line treatment to help reduce thyroid hormone levels.

Once hormone levels reduce, a person may require surgery to remove thyroid nodules or all or part of the thyroid gland.

A doctor may also recommend radioactive iodine therapy. This involves ingesting radioactive iodine to destroy overactive thyroid gland cells.

A person may also need to avoid:

  • foods that contain high amounts of iodine, such as seaweed
  • iodine supplements
  • multivitamins
  • cough syrups

Treatment for tachycardia focuses on treating the underlying cause. Therefore, if hyperthyroidism has led to tachycardia, the main goal will be to treat hyperthyroidism, which may then help treat tachycardia.

If a person experiences symptoms of hyperthyroidism, they should speak with a doctor who can order a thyroid test.

Symptoms of hyperthyroidism may include:

Tachycardia

A person with tachycardia may not experience any symptoms. However, a person with hyperthyroidism should speak to a doctor if they experience any tachycardia symptoms, including:

Hyperthyroidism can occur when the body produces too much thyroid hormone. This can be due to an autoimmune condition known as Graves’ disease, the body producing or ingesting too much iodine, inflammation of the thyroid gland, and overactive thyroid nodules.

Tachycardia is the medical term for a fast heartbeat — over 100 beats per minute when a person is at rest.

Hyperthyroidism may lead to tachycardia, as high levels of thyroid hormone can increase a person’s heart rate. However, some research suggests that tachycardia in people with hyperthyroidism may now be less common due to doctors more frequently recommending thyroid function tests.

A person should speak with a doctor if they experience any symptoms of hyperthyroidism or tachycardia. A healthcare professional can perform diagnostic tests and recommend appropriate treatment.