Thyroid Disorders & Heart Disease

Reviewed By:
Nikheel Kolatkar, M.D.
Abdou Elhendy, MD, PhD, FACC, FAHA
Robert I. Hamby, M.D., FACC, FACP

Summary

About thyroid disorders and heart disease

Types and differences of thyroid disorders

Risk factors and causes of thyroid disorders

Many factors can affect the functioning of the thyroid gland and cause thyroid disorders.

For example, imbalances in iodine levels (either a deficiency or a surplus) may lead to goiter, hypothyroidism or hyperthyroidism. Viral infections cause some types of thyroiditis. There are also autoimmune disorders, such as Hashimoto’s thyroiditis, which causes hypothyroidism, and Graves' disease, which causes hyperthyroidism.

Use of certain medications sometimes causes thyroid disorders. This may include amiodarone (antiarrhythmic heart drug), lithium (bipolar disorder drug), and interferon alpha and interleukin-2 (cancer drugs).

Surgical removal of part or all of the thyroid gland, or damage done to the gland as a part of treatment for other conditions (e.g., using radioactive iodine to treat goiter, hyperthyroidism or thyroid cancer) may cause hypothyroidism. Damage to the pituitary gland, which communicates with the thyroid gland, may also cause some types of thyroid disorders.

Women who are pregnant may produce antibodies to their own thyroid gland that can lead to hypothyroidism and increases the risk of miscarriage, premature delivery and preeclampsia, a serious disorder of late pregnancy that involves high blood pressure, swelling and protein in the urine. After giving birth, women can experience a temporary thyroid disorder known as postpartum thyroiditis.

>The cause of many cases of thyroid disorders remains unknown.

Risk factors that put a person at an increased risk of developing thyroid disorders include:

• Sex. Women develop thyroid disorders more frequently than men.
  
  
• Age. Many thyroid disorders are more likely to affect people over the age of 40. Hypothyroidism is particularly common after age 60.
  
  
• Family history. People with a family history of thyroid disorders may be more likely to develop thyroid disorders.
  
  
• Down syndrome. Hypothyroidism, along with an enlarged thyroid gland, occurs more frequently in people born with Down syndrome.

Signs and symptoms of thyroid disorders

The signs and symptoms of thyroid disorders can vary significantly from person to person. They may also vary depending on the type of thyroid disorder present. For example, hypothyroidism commonly includes symptoms such as fatigue, a slow heart rate, weight gain, feeling cold, muscle cramps, heavy menstrual flow and constipation. In contrast, hyperthyroidism may include symptoms such as a fast heart rate, weight loss, increased perspiration, muscle weakness, decreased menstrual flow and increased frequency of bowel movements.

In the case of goiter, thyroid nodules or thyroid cancer, symptoms may include a lump at the front of the neck, swollen lymph nodes, difficulty swallowing or breathing, hoarseness, and pain in the throat or neck. However, in many patients, these thyroid disorders do not cause symptoms. Symptoms of thyroiditis can vary, depending on the type of thyroiditis involved. For example, Hashimoto’s thyroiditis involves symptoms that are similar to hypothyroidism.

Thyroid disorders may affect the heart, causing problems such as high blood pressure and high cholesterol. In some cases, atrial fibrillation may occur. Symptoms of heart involvement associated with thyroid disorders may vary, depending on the type of thyroid disorder present.

The most common cardiac symptoms of hypothyroidism include:

• Bradycardia (slow heart rate). Thyroid hormones help regulate the heart rate. When there is not enough hormone production the heart can beat 10 to 20 beats slower than normal.
  
  
• Shortness of breath during physical exertion. When this symptom occurs in patients with heart disease, it may indicate skeletal muscle weakening or a worsening of heart failure.
  
  
• Diastolic hypertension. Even though hypothyroidism slows a person’s metabolism, it can cause high diastolic blood pressure due to the stiffening of the arteries.
  
  
• Onset or worsening of heart failure. Hypothyroidism can cause individuals with mild heart disease to have heart failure for the first time. In people with well-controlled heart failure, it can cause it to become worse.
  
  
• Worsening of coronary artery disease (CAD). Hypothyroidism can cause patients with angina (cardiac chest pain) to have increased levels of LDL cholesterol and C-reactive proteins. These elements can accelerate underlying CAD.

The most common cardiac symptoms of hyperthyroidism include:

• Tachycardia (fast heart rate). With mild exertion, people with hyperthyroidism can have an increased heart rate at rest and during mild exertion. It can also produce a number of other arrhythmias, including atrial fibrillation and premature ventricular contraction (PVC).
  
  
• Angina. This may occur after hyperthyroidism develops, or if it already exists in patients with heart disease, it may be worsened with hyperthyroidism. Individuals with CAD have a risk of experiencing increased chest pain or a heart attack.
  
  
• Shortness of breath. As with hypothyroidism, difficulty breathing can be a symptom of muscle weakness or a worsening of heart failure.
  
  
• Systolic hypertension. Stronger heart contractions cause the systolic blood pressure to increase, although relaxed blood vessels help reduce diastolic blood pressure.

People who suspect they may have a thyroid disorder should consult their physician. Anyone experiencing the cardiac symptoms mentioned above should seek immediate medical attention.

Some patients have no symptoms of a thyroid disorder. The American Thyroid Association recommends that all people be routinely screened for thyroid dysfunction beginning at the age of 35 and every five years thereafter.

Diagnosis methods for thyroid disorders

Diagnosis of thyroid disorders begins with a physical examination by a physician, paying careful attention to a patient’s head and neck. A physician typically also compiles a medical history of the patient, which may include questions about symptoms and whether there is a family history of similar symptoms or thyroid disorders.

Tests that may be performed to help diagnosis thyroid disorders that may affect the heart include:

• Thyroid blood tests. These lab tests measure levels of thyroid hormones as well as thyroid stimulating hormone (TSH), which is produced by the pituitary gland. Testing may be performed to help diagnose some types of thyroid disorders, as well as to monitor patients being treated for thyroid disorders.
  
  
• Thyroid imaging tests. Procedures such as a thyroid scan may be used to identify whether inflammation (thyroiditis) or enlargement (goiter) of the gland exists. They may also identify the presence of thyroid nodules or cancer. A thyroid scan may be performed with or without the use of radioactive iodine.
  
  
• Biopsy. A sample of tissue from the thyroid gland, usually taken with a needle, may be analyzed by a laboratory.
  
  
• Chest x-ray. This painless imaging test can help a physician determine whether a patient has an enlarged heart, which may be a sign of a thyroid disorder.
  
  
• Electrocardiogram (EKG or ECG). If a patient experiences heart-related symptoms, such as palpitations or chest pain, an EKG will likely be performed. The EKG is a recording of the heart’s electrical activity. It may be used to identify heart irregularities, disease or damage by measuring the heart’s rhythms and electrical impulses.

Patients suspected of having a thyroid disorder may be referred to an endocrinologist (physician specializing in disorders of the endocrine system).

Treatment and prevention of thyroid disorders

Although there is no cure for most thyroid disorders, there are a variety of effective treatment options available. With proper treatment and medical management, most patients with thyroid disorders can expect to lead full, active lives.

Early diagnosis and treatment of a thyroid disorder may help control the condition, sometimes even before symptoms develop. Treatment methods will depend on the type of thyroid disorder present. For example, the goal of treating hypothyroidism and hyperthyroidism is to restore normal levels of thyroid hormones in the body.

In most cases, treatment is achieved through the use of medications. The type of medications used will depend on the type of thyroid disorder, as well as a patient’s general health, other medical conditions present, age and severity of symptoms. Patients may have to take these medications for the rest of their lives and have their condition periodically monitored by a physician.

In many cases, once a patient finds a thyroid medication that treats the disorder, the patient usually sticks to that formulation permanently. However, there are subtle differences from one type of medication to another that may result in a need to modify the medication regimen.

Some thyroid disorders (e.g., goiters) may resolve on their own without treatment. In other cases (e.g., obstructive goiters, thyroid cancer, some cases of hyperthyroidism), surgery may be recommended to remove part or all of the thyroid gland.

Radioactive iodine therapy is a common treatment for some types of thyroid disorders. Radioactive iodine emits radiation that is harmful to thyroid cells. This type of treatment involves oral administration of the iodine, which is slowly absorbed by the thyroid gland and eventually damages the cells of the gland that make thyroid hormones. This reduces the level of thyroid hormone in the blood. It may also shrink the thyroid gland or thyroid nodules.

Radioactive iodine therapy may be used to treat hyperthyroidism or certain cases of goiter. Larger doses of I-131 may be used to destroy any remaining cancer cells after surgical removal of the thyroid gland for thyroid cancer. Such removal may help prevent recurrence of the cancer.

However, any procedure that removes or damages part or all of the thyroid gland often causes hypothyroidism, which then needs to be treated with medications.

The ability to prevent thyroid disorders depends on the type of disorder. For example, some cases of goiter are caused by an iodine deficiency, though this is rare in the United States. Ensuring adequate levels of iodine can help prevent goiter. It is important that patients consult a physician about proper iodine levels, because too little or too much of the mineral may also cause thyroid problems. In addition, limiting exposure to radiation may help prevent thyroid cancer.

Although functional problems of the thyroid gland, such as hypothyroidism or hyperthyroidism, may not be preventable, the symptoms may be managed and complications prevented with proper treatment and monitoring.

Questions for your doctor