Hyperthyroidism causes the body to produce too much thyroid hormone. People with this condition may have cardiovascular conditions such as high blood pressure, also known as hypertension.

The thyroid gland plays an important role in how the body uses energy. If it overproduces thyroid hormone, it can speed up bodily functions, such as the heart rate. As a result, this can cause increased blood pressure.

According to the American Thyroid Association (ATA), people are also at increased risk of coronary artery disease, stroke, heart failure, and atrial fibrillation — an irregular heart rhythm.

Read on to learn how thyroid conditions affect blood pressure, symptoms, risk factors, treatment options, and more.

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Hyperthyroidism is a condition that causes a person’s thyroid gland to produce too much thyroid hormone.

The thyroid is a small, butterfly-shaped gland that sits at the front of the neck. It is sometimes called overactive thyroid. This condition is the opposite of hypothyroidism — an underactive thyroid.

Thyroid hormones control energy metabolism, which is the way the body uses energy. This means they affect almost every organ, including the heart.

Over the past few decades, researchers have explored the effects of hypothalamus-pituitary-thyroid (HPT) axis genetic mutations on the cardiovascular system. The HPT axis is responsible for maintaining the usual circulating levels of thyroid hormone.

The ATA reports that people with hyperthyroidism are at increased risk of a range of cardiovascular conditions, including:

Additionally, a 2020 study found that hyperthyroidism can increase:

  • Cardiac output: The amount of blood the heart pumps each minute.
  • Systolic blood pressure: The force generated by the heart pumping blood around the body.
  • Renin, angiotensin, and aldosterone levels: These are essential substances for regulating blood volume and the force on the blood vessels of the circulating blood.

If a person’s hypertension is due to hyperthyroidism, treating the thyroid condition can resolve both issues.

The symptoms of hyperthyroidism reflect the overactive metabolism that the disease causes. Therefore, common symptoms of hyperthyroidism include:

A person may also:

Learn more about the signs and symptoms of hyperthyroidism.

Being a biological female and being over 60 years old increase a person’s risk of hyperthyroidism. A person is also more likely to have hyperthyroidism if they have a pre-existing health condition such as pernicious anemia, type 2 diabetes, or primary adrenal insufficiency.

Other risk factors include:

  • having a family history of thyroid disease
  • eating a diet rich in iodine, such as kelp
  • taking medication that contain iodine
  • using nicotine, such as smoking or vaping
  • being pregnant within the previous 6 months

Doctors treat a person’s hyperthyroidism according to the underlying cause and severity of the condition. Different treatment options work for different people — there is no one-size-fits-all approach. However, the aim of any treatment is to bring thyroid hormones back down to typical levels.

The three main treatment types for hyperthyroidism include medication, radioiodine therapy, and thyroid surgery.

Thyroid medications

Doctors may prescribe medications such as beta-blockers to treat the effects of hyperthyroidism. Beta-blockers work mainly in the heart to prevent substances, such as adrenaline, from affecting nerve cells. This treatment reduces blood pressure and heart rate, which can help to reduce palpitations and anxiety.

However, beta-blockers do not affect on thyroid hormone production.

Antithyroid medication reduces thyroid hormone production and may temporarily reduce Graves’ disease symptoms. This is an autoimmune condition causing hyperthyroidism.

Doctors most commonly prescribe methimazole, but if a person is pregnant, they may recommend propylthiouracil. In rare cases, methimazole may harm the fetus.

Some people experience side effects from taking antithyroid medicines, including:

  • an adverse reaction, such as a rash and itching
  • a reduction in white blood cells, which can lower immune defenses and reduce resistance to infection
  • in rare cases, liver failure

Radioiodine therapy

Radioiodine therapy slowly kills off the cells that produce thyroid hormone. It does not affect other tissues in the body. People take this treatment orally in capsule or liquid form.

Doctors do not prescribe radioiodine therapy during pregnancy as it can harm the fetus.

A person is extremely likely to develop hypothyroidism following radioiodine therapy. However, doctors consider hypothyroidism easier to treat than hyperthyroidism. Therefore, they may decide this is the right choice for some individuals.

Thyroid surgery

If a person has a goiter — a swollen neck due to enlargement of the thyroid gland — doctors may recommend surgery. They may also suggest it for a person with hyperthyroidism during pregnancy when other treatments are potentially harmful or inadequate.

Depending on the individual and how much of the thyroid gland surgeons remove, a person may develop hypothyroidism and require medications to treat this condition.

It is important for a doctor to check a person’s thyroid function if they are experiencing any of the previously mentioned symptoms, including palpitations, diarrhea, and excessive sweating.

If a person experiences any of the following symptoms after taking thyroid medication, they should contact their doctor immediately:

Hyperthyroidism causes the thyroid gland to produce too much thyroid hormone. This speeds up a range of essential body functions, including heart rate.

Therefore, it may increase a person’s risk for cardiovascular issues, such as raised blood pressure, irregular heart rhythm, or stroke. Treatments include medications, radioiodine therapy, or surgery.