Hyperthyroidism (overactive thyroid) occurs when the thyroid gland located in the neck produces excess thyroid hormone, which increases the body’s metabolism.
Hyperthyroidism is not the same condition as hypothyroidism (underactive thyroid), which is when a person produces too little thyroid hormone.
Hyperthyroidism is treated with medications, radioiodine, or surgery. The best medication for hyperthyroidism is based on the cause of the condition and the patient’s symptoms and can vary depending on the patient.
Medications used to treat hyperthyroidism include:
- Antithyroid drugs that work by decreasing how much thyroid hormone the body produces
- Methimazole (MMI or Tapazole)
- Propylthiouracil (PTU)
- Beta-blockers to help control certain hyperthyroidism symptoms such as rapid heart rate, anxiety, tremors, and heat intolerance
- Atenolol (Tenormin)
- Propranolol (Inderal)
Radioactive iodine is used to destroy the thyroid with radioiodine in a process called ablation.
- This is the most widely used treatment for hyperthyroidism in the U.S.
- It is a permanent way to treat hyperthyroidism
- The dose of radiation used is small and it does not cause cancer, infertility, or birth defects
Surgery is used in certain cases, such as when:
What Are Symptoms of Hyperthyroidism?
Some people with hyperthyroidism (overactive thyroid) may have no symptoms. Symptoms of hyperthyroidism may include:
- Anxiety
- Irritability
- Tremors of the hands
- Heat intolerance
- Trouble sleeping
- Fast or uneven heartbeats
- Weakness (especially in the upper arms and thighs, which can make it difficult to lift heavy things or climb stairs)
- Sweating more than usual
- Tiredness/fatigue
- Weight loss even with a normal or increased appetite
- Frequent bowel movements
- Irregular or missed menstrual periods, which may be associated with infertility
- Swelling in the neck (goiter)
- Bulging eyes (if hyperthyroidism is caused by Graves' disease)
- Breast tissue growth in men
- Erectile dysfunction (impotence)
- Atrial fibrillation, chest pain, and rarely, heart failure if untreated
What Causes Hyperthyroidism?
The most common cause of hyperthyroidism (overactive thyroid) is Graves' disease, a condition in which the immune system produces an antibody that stimulates the thyroid gland to produce excess thyroid hormone.
Other causes of hyperthyroidism include:
- Thyroid nodules (small growths or lumps in the thyroid gland) that can produce too much thyroid hormone (called a hot nodule or toxic nodule when there is a single nodule, or a toxic nodular goiter when there is more than one nodule)
- Painless (“silent or lymphocytic”) thyroiditis, a condition in which the thyroid becomes temporarily inflamed and releases thyroid hormone into the bloodstream
- Postpartum thyroiditis which can occur several months after delivery and can cause the thyroid to become temporarily inflamed and release thyroid hormone into the bloodstream
- Subacute (granulomatous) thyroiditis which is believed to be caused by a virus
- Taking too much thyroid hormone medication for hypothyroidism which can increase thyroid blood levels
How Is Hyperthyroidism Diagnosed?
In addition to a patient history and physical examination, hyperthyroidism (overactive thyroid) is diagnosed with blood tests that measure the amount of thyroid hormone and thyroid-stimulating hormone (TSH).
Other tests may include:
- Thyroid scan
- Blood test to help determine the cause of hyperthyroidism (such as Graves' disease, toxic nodular goiter, or thyroiditis)
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