Hyperthyroidism, the result of an overactive thyroid, more commonly affects women between the ages of 20 and 40, but men can also develop this condition. The symptoms of this thyroid condition can be frightening.
Symptoms can include:
Diarrhea or frequent bowel movements
Irritability and anxiety
Vision problems (irritated eyes or difficulty seeing)
Intolerance to heat and increased sweating
Graves' disease is the most common cause of hyperthyroidism. It occurs when the immune system produces antibodies that attack the thyroid gland, making it produce too much thyroid hormone and creating a hormone imbalance. This condition happens often in people with a family history of thyroid disease. In some patients with Graves' disease, one of the noticeable symptoms may be swelling behind the eyes, causing discomfort or increased tearing or causing the eyes to push forward or bulge.
Other causes of hyperthyroidism include the following:
Thyroid nodules. (Read more on THYROID NODULES.)
Taking too much thyroid hormone medication to treat other conditions.
Subacute thyroiditis. This painful inflammation of the thyroid is usually caused by a virus. When the infection leaves, the condition improves.
Lymphocytic thyroiditis and postpartum thyroiditis. These related autoimmune disorders cause a temporary painless inflammation of the gland. Thyroiditis is marked by lymphocytes (white blood cells) inside the thyroid and leads to leakage of thyroid hormone from the infmlamed gland, raising hormone levels in the bloodstream.
Antithyroid Drugs: These drugs work to decrease the amount of hormone the thyroid gland makes. For most patients, the preferred drug is methimazole because of its safety record. Another drug, propylthiouracil (PTU) may be preferred for patients who are allergic to or intolerant of methimazole and for pregnant women in their first trimester of pregnancy.
Antithyroid drugs may have to be taken for an extended period - even one to two years or longer. The thyroid condition may go away, but there could be a relapse, even years later. Therapy with antithyroid drugs is typically thought of as either short term or long term. Short-term therapy is used to make the thyroid blood tests normal before a decision is reached about definitive therapy. Long-term therapy is used in some patients to try to make the disease go into remission even after the antithyroid drug is stopped.
Beta-blockers: Beta-blocker drugs, such as atenolol, do not block the production of thyroid hormone. Instead, they control many troubling symptoms of this hormone imbalance, especially rapid heart rate, trembling, anxiety, and the high amount of heat the body produces with this condition.
Radioactive iodine: The thyroid gland normally collects iodine out of the bloodstream to make thyroid hormone. Radioactive iodine treatment involves taking a radioactive form of iodine that causes the permanent destruction of the thyroid. The response to treatment can take from 6 to 18 weeks. Because the radioiodine often destroys some of the normal function of the thyroid gland, people who have this therapy will likely need to take thyroid hormone for the rest of their lives to replace their hormone levels. Most physicians agree that the desirable goal of radioactive therapy is to completely remove thyroid gland function since then there is a very low chance of hyperthyroidism coming back.
Surgery: Removal of the thyroid gland (thyroidectomy) is another permanent solution, but is often the least preferred option. This procedure must be performed by a highly skilled and experienced thyroid surgeon because of the risk of damage to nerves around the larynx (voice box) and to the nearby parathyroid glands, which control calcium metabolism in the body. Surgery is recommended when there is a large goiter (enlarged thyroid gland) that makes breathing difficult or when antithyroid drugs are not working, or when there are reasons not to take radioactive iodine. It may also be used in patients who also have thyroid nodules, especially when the nodules may be cancerous. In the latter instance, additional thyroid cancer treatment is often required.
After both radioactive iodine and surgery treatments, the patient will need to be monitored regularly for adequate thyroid hormone levels in the blood. After such treatment, most patients become hypothyroid and no longer produce enough thyroid hormone. For this reason, they must take a daily supplement of synthetic thyroid hormone to correct the hormone imbalance.
If left untreated, hyperthyroidism can lead to other health problems including congestive heart failure as well as osteoporosis, which causes brittle bones.
© 2012 The Hormone Foundation. All rights reserved.