Body attacks itself in Graves' disease

Q: What is Graves' disease?

A: Graves' disease is the most common cause of hyperthyroidism, an overabundance of thyroid hormones in the body. Your thyroid gland produces these hormones, which control all aspects of your metabolism, including your heart rate and how quickly you burn calories.

Graves' disease was named for Robert Graves, the Irish physician who first identified it.

It is an autoimmune disorder, which means the body's immune system mistakenly attacks the body's own cells rather than protecting them from outside invaders.

In Graves' disease, the immune system produces substances that stimulate the thyroid gland to make too much thyroid hormone. The disease runs in families and occurs more often in women, usually between the ages of 20 and 50.

Sometimes, but not always, the thyroid gland enlarges and may protrude from the neck to form what is known as a goiter.

If the goiter is large enough, it may feel lumpy. But the size of the gland doesn't necessarily predict how much hormone it will produce.

For instance, some people have barely enlarged thyroid glands that put out enormous amounts of hormone. Others have fairly big goiters that overproduce thyroid hormones by only modest amounts.

Excess thyroid hormone can trigger a wide range of symptoms. The prefix "hyper-" can mean "above, over and excessive" or, as a word, "high-strung and keyed up." Both definitions describe the effect hyperthyroidism has on the body.

Because the condition speeds up metabolism, body temperature rises. So people who are hyperthyroid often feel warm. Their sweat glands tend to overproduce, so the skin is warm, moist and flushed. They also may feel extremely hungry yet still lose weight. The overactivity of the digestive system can lead to frequent, loose bowel movements.

Other symptoms include a racing heart or abnormal heart rhythms. Hand tremors, which result from overstimulated nerves, also can occur. People with the condition also may feel weak, tired and anxious or irritable. Graves' disease also can cause the eyelids to retract, which makes the eyes appear to bulge or stare dramatically. The eyes also may be puffy and watery.

Graves' occasionally improves on its own, but most patients need treatment. Therapy focuses on two goals: improving symptoms and slowing the thyroid's production of hormone.

Symptoms such as rapid heart rates, tremors and nervousness are treated with medications known as beta-blockers, such as propanolol (Inderal). For anxiety and insomnia, doctors may prescribe diazepam (Valium), lorazepam (Ativan) or a similar medication.

To stop the thyroid from producing too much hormone, there are three possible treatments: antithyroid medications, radioactive iodine and surgery.

Many patients with Graves' disease begin treatment with an anti-thyroid medication, such as methimazole (Tapazole, Thiamazole) or propylthiouracil (sold as a generic). Once thyroid hormone levels have come down to normal, a person can either continue daily anti-thyroid medication or choose radioactive iodine treatment.

Radioactive iodine is given by mouth. Most specialists recommend a large-enough dose to stop the thyroid from producing any hormone at all. This requires taking thyroid-replacement medication daily for life. Because people who receive radioactive iodine therapy temporarily store a small amount of radiation in their thyroids, they need to avoid prolonged contact with children and pregnant women for several days following treatment. Radioactive iodine is concentrated in breast milk, so women must stop breast-feeding if they choose this therapy.

Surgery for Graves' disease is rarely done today. However, people with very large goiters are less likely to respond well to anti-thyroid medication or radioactive iodine. They may have a better outcome if most of the thyroid gland is removed surgically.

Patients with eye signs of Graves' disease may be given eye drops to keep the eyes moist and tinted eyeglasses to protect the eyes from sun, wind and dust. Some benefit from anti-inflammatory medication.

It can be complex, and doctors often call on endocrinologists to plan and direct therapy. But in most cases, treatment will prevent Graves' disease from having grave consequences for health.

The Harvard Medical School Adviser is researched and written by the faculty and staff of Harvard Medical School. Visit www.health.harvard.edu/adviser.