Hyperthyroidism

Signs and Symptoms

Hyperthyroidism occurs when the thyroid produces excess thyroid hormone. The thyroid gland is located in the neck and produces several hormones, which control metabolism, or the way cells use energy. Hyperthyroidism is a common disorder affecting over two million Americans, most of whom are women.

The most common cause of the condition is Graves' disease, which accounts for 85 percent of cases. Hyperthyroidism also can result from nodular goiter, a condition in which an inflammation of the thyroid occurs due to viral infections or other causes, ingestion of excessive amounts of thyroid hormone, and ingestion of excessive iodine.

Initially, many patients do not experience any symptoms and therefore do not get diagnosed with hyperthyroidism until it is more advanced. In older people, some or all of the typical symptoms of hyperthyroidism may be absent, and the patient may just lose weight or become depressed. Typical symptoms of the condition include:

• Nervousness and irritability
• Increased resting heart rate, which causes heart palpitations
• Heat intolerance and increased sweating
• Tremors
• Weight loss with increase in appetite
• Frequent bowel movements
• Thyroid enlargement causing a lump in the neck
• Pretibial myxdemia, which causes a thick redness on the front of legs and typically occurs with Graves' disease
• Thin, delicate skin and irregular fingernail and hair growth
• Menstrual disturbance, such as decreased flow
• Mental disturbances
• Sleep disturbances, including insomnia
• Changes in vision, eye irritation or exophthalmos, which is a protrusion of the eyes that typically occurs with Graves' disease

Diagnosis

Your doctor will first perform a physical examination to check for any obvious symptoms of hyperthyroidism. In addition, your doctor may run other tests, including:

• Blood Tests -- Blood tests are performed that measure the levels of the thyroid hormones, T4 and T3, which must be high to make a diagnosis of hyperthyroidism. The level of thyroid stimulating hormone (TSH) also is measured. With hyperthyroidism TSH is low while T4 and T3 levels are high.

• Iodine Uptake Scan -- This test measures thyroid function by determining how much iodine is taken up by the thyroid gland. Patients are given a small dose of radioactive iodine that is taken on an empty stomach. The iodine is concentrated in the thyroid gland or excreted in the urine over the next few hours. The amount of iodine that goes into the thyroid gland is then measured.

• Thyroid Scan -- This test typically is performed at the same time as the iodine uptake test because it also requires that a patient take radioactive iodine, which then concentrates in the thyroid gland. Thyroid scans use the emissions of gamma rays from radioactive iodine to obtain a picture of the thyroid.

Treatment

Treatment varies depending on the cause of hyperthyroidism and the severity of symptoms. Treatment options include:

• Antithyroid Medications -- Antithyroid drugs may be prescribed to suppress the production and release of thyroid hormones by inhibiting the use of iodine by the thyroid. Side effects may include skin rash, joint pains, fever, low white count and jaundice.

• Radioactive Iodine -- This is the preferred treatment of hyperthyroidism caused by Graves' disease. A radioactive iodine tablet is ingested and then taken up by thyroid cells. These overactive cells are damaged so that the thyroid can shrink in size and produce hormones at normal levels. Although this is a safe treatment, most people eventually become hypothyroid after radioactive iodine therapy and therefore require lifelong thyroid hormone replacement therapy. Radioactive iodine therapy cannot be given to pregnant women or those who are breastfeeding.

• Surgery -- In severe cases, surgery to remove the thyroid, called thyroidectomy, may be performed. If the thyroid is removed, replacement thyroid hormones must be taken for the rest of a person's life. Candidates for surgery may include pregnant hyperthyroid patients intolerant of antithyroid drugs, patients desiring definitive therapy without the use of radioactive iodine, children and patients with very large or nodular goiters.

• Other Medications -- Occasionally, drugs known as beta adrenergic blocking agents are prescribed to block the action of thyroid hormone on the heart and thus relieve symptoms. Unless the hyperthyroidism is caused by thyroiditis, these drugs are used in conjunction with other treatments.