The good news is Hashimoto's is relatively easy to diagnose. Blood tests are done to look for specific antibodies, namely, thyroid peroxidase antibodies (TPOAb) and, in some cases, thyroglobulin antibodies (TgAb). TPOAb attack an enzyme called thyroid peroxidase inside the thyroid cells, which is involved in the uptake of iodine to produce thyroid hormone. TgAb destroy thyroglobulin, the protein that stores thyroid hormone, and disrupts the process of hormone production. In general, if TPO antibodies are measured, TgAb do not need to be measured. Oddly enough, the same antibodies that cause Hashimoto's can also cause Graves' disease.

Studies have suggested that about 10 percent of the population has low levels of these autoantibodies in their blood, but most of these people have no symptoms or health problems. In people with Hashimoto's, however, the levels are significantly higher.

In addition to autoantibodies, your doctor will probably test your TSH levels. Elevated levels of TSH are a key indicator of hypothyroidism. Even a slight reduction in the amount of thyroid hormone being produced can cause your TSH levels to rise. Some people with normal levels of TSH, however, can still have autoantibodies in their blood.

Some doctors may do a fine needle aspiration (FNA) of your thyroid, especially if you have a nodule as well as a goiter. The cells removed from your thyroid gland are then examined under a microscope for the presence of abnormal white blood cells. An FNA is rarely done except in cases that are difficult to diagnose and to rule out the possibility of cancer.

In people who have Hashimoto's that starts off with hyperthyroidism, the disease can be harder to diagnose. Since some of the same autoantibodies are also present in Graves' disease, your doctor may mistakenly diagnose you with Graves'. One way to distinguish Graves' from Hashimoto's is with a free T4 test. In people with Hashitoxicosis, levels of free T4 will gradually diminish as the thyroid hormone dissipates.

In some cases, an RAI uptake test can also help confirm Hashimoto's. This test involves ingesting a small amount of RAI. Hours later, a camera is placed in front of your neck to see where the iodine is concentrated. People with Hashitoxicosis will have a low RAI uptake result because the thyroid isn't working well and can't absorb much of the RAI. But in people with Graves' disease, the RAI uptake test will be high because the thyroid is absorbing a lot of iodine to produce thyroid hormone.

Although Hashimoto's has no cure, the treatment is fairly simple. You'll need thyroid hormone replacement to replenish your body's missing hormones. Taking replacement hormone will ease the symptoms of hypothyroidism, and in patients who have no symptoms yet, may even prevent hypothyroidism from developing at all.

The replacement hormone also halts the excess release of TSH from the pituitary gland, thereby preventing a goiter from developing. In patients who already have a goiter, the drugs can cause the goiter to shrink, though it may take as long as eighteen months.

In some people, the drugs will have no impact on a goiter, and you may need to have your thyroid gland removed. For more information on thyroid hormone replacement, see Chapter 5.

Some doctors may be reluctant to treat you if your TSH levels are normal, despite the presence of autoantibodies that suggest you have Hashimoto's. Other doctors may be willing to start treatment based solely on the presence of autoantibodies. Research suggests that treatment may actually slow the progression of Hashimoto's. A study published in 2001 found that treating people who had normal levels of TSH and autoantibodies for Hashimoto's for a year actually slowed the progression of disease. Upon testing, they found that the people who took levothyroxine had fewer markers for autoimmune disease compared with the patients who did not receive levothyroxine.