Genetic: Hashimoto Disease

Definition
Description
Demographics
Causes and Symptoms
Diagnosis
Treatment
Prognosis
Prevention
The Future
For more information

Definition

Hashimoto disease is an autoimmune disorder in which the body's immune system attacks the cells and tissues of the thyroid gland, a hormone-secreting (also called endocrine) gland resembling a butterfly located at the base of the neck just below the Adam's apple.

Description

Hashimoto disease is caused by autoimmune damage to the thyroid gland at the base of the neck. The gland may become swollen—a condition known as goiter—or it may remain normal in size. In either case it becomes inflamed, and its cells begin to die. This loss of tissue means that the gland no longer produces enough thyroid hormone, a chemical that the body needs to regulate its metabolism. This condition is known as hypothyroidism.

Demographics

Hashimoto disease is the most common cause of hypothyroidism in the United States and Canada in people over six years of age. It is largely a disease of adulthood, with the rate increasing with age. The most commonly affected age group is middle-aged adults between thirty and fifty.

Hashimoto disease is diagnosed in about fourteen women out of every 1,000 and one man in every 2,000. The disorder is estimated to be between ten and twenty times more common in women than in men, for reasons that are not yet known. It appears to be equally frequent in all races and ethnic groups, however.

Causes and Symptoms

Although doctors know that Hashimoto disease is an autoimmune disorder, they do not know what triggers its onset. Some think that the

disease is related to a gene known as HLA-DR5; however, different genes seem to be related to the appearance of the disease in different ethnic groups. It is known that the disease tends to run in families.

Other researchers think that a bacterium or virus may be the cause of the autoimmune response in Hashimoto's disease. In any case, the auto-immune processes cause the destruction of the cells in the thyroid gland, leading to a drop in the production of thyroid hormone and the characteristic symptoms of hypothyroidism.

The symptoms of Hashimoto disease are not specific to it; that is, they can be caused by other diseases or disorders. In addition, the symptoms typically come on gradually; the person may simply feel tired or less energetic than usual or develop dry, itchy skin and brittle hair that falls out easily. It may take months to years before the person or their doctor begins to suspect a problem with the thyroid gland.

Some patients with Hashimoto disease, however, have an early phase of the disease in which they have too much thyroid hormone in their bloodstream; this temporary hyperthyroidism is caused by the leaking of thyroid hormone from damaged cells in the gland. This condition is called hashitoxicosis and is characterized by anxiety, heavy sweating, restlessness, diarrhea, high blood pressure, and a general feeling of being keyed up. Eventually the damaged thyroid cells die, however, and the level of thyroid hormone in the blood drops below normal.

Typical symptoms of Hashimoto disease include the following:

• Cold, dry skin and increased sensitivity to cold weather
• Dry brittle hair that falls out easily
• Constipation
• Hoarse voice and puffy face
• Unexplained weight gain of 10–20 pounds (4.5–9 kilograms), most of which is fluid
• Sore and aching muscles, most commonly in the shoulders and hips
• In women, extra-long menstrual periods or unusually heavy bleeding
• Weak leg muscles
• Memory loss
• Depression

Diagnosis

The diagnosis of Hashimoto disease is usually made by tests of the patient's thyroid function. The first test is a hormone test for thyroid-stimulating hormone, or TSH. TSH is a hormone produced by the pituitary gland in the brain that stimulates the thyroid gland to produce thyroid hormone. When the thyroid gland is not producing enough hormone, the pituitary gland secretes more TSH; thus a high level of TSH in the blood indicates that the thyroid gland is not as active as it should be. Another type of blood test involves testing for the presence of abnormal antibodies. Because Hashimoto disease is an autoimmune disorder, there will be two or three types of anti-thyroid antibodies in the patient's blood in about 90 percent of cases.

Haraku Hashimoto (1881–1934)

Haraku Hashimoto was born into a family of medical doctors in the small village of Midau on the island of Honshu, Japan. He entered the new medical school at Kyushu University at the age of 22, graduating with one of its first classes in 1907. He intended to specialize in surgery, studying under Hayari Miyake (1867– 1945), the first Japanese neurosurgeon.

Hashimoto then went to Germany for postgraduate study. He published a paper in 1912 in a German medical journal on four cases of a disorder of the thyroid gland, noting the characteristic abnormalities of the gland's tissue that are still used in diagnosing the disease later named after him. Although Japanese doctors were unaware of Hashimoto's discovery, because it had been published in a German journal, English and American doctors who read the journal recognized that Hashimoto was describing a distinctive disorder, which they named Hashimoto's thyroiditis. Hashimoto himself continued to study in German and English hospitals until 1914, when his father died and he returned to Japan to take up his father's medical practice.

He specialized in major abdominal surgery after his return to Japan rather than continuing to work on disorders of the thyroid. He was only 53 when he died of typhoid fever in 1934.

The doctor may also order an ultrasound study of the patient's neck in order to evaluate the size of the thyroid gland or take a small sample of thyroid tissue in order to make sure that the gland is not cancerous. Thyroid tissue that has been affected by Hashimoto's disease has a

distinctive pattern of broken cells and other types of tissue damage that will confirm the diagnosis.

Treatment

Treatment for Hashimoto disease consists of a daily dose of a synthetic form of thyroid hormone known as levothyroxine, sold under the trade names of Synthroid, Levothroid, or Levoxyl. The patient is told that the drug must be taken as directed for the rest of his or her life.

In the early weeks of treatment, the patient will need to see the doctor every six to eight weeks to have their TSH level checked and the dose of medication adjusted. After the doctor is satisfied with the dosage level and the patient's overall health, checkups are done every six to twelve months. The reason for this careful measurement of the medication is that too much levothyroxine increases the risk of osteoporosis in later life or abnormal heart rhythms in the present.

Prognosis

The prognosis for patients with Hashimoto disease is excellent, provided they take their medication as directed. They can usually live a normal life with a normal life expectancy.

The chief risks to health with Hashimoto disease are related to lack of treatment for the disorder. If this type of thyroiditis is not diagnosed and treated, patients are at increased risk of goiter, an enlarged heart, and severe depression. In addition, women with untreated Hashimoto disease have a higher risk of giving birth to babies with cleft palate and other birth defects.

Prevention

There is no known way to prevent Hashimoto disease because the cause is not yet completely understood.

The Future

The incidence of Hashimoto disease is not likely to increase in the foreseeable future. Research of the disorder is likely to focus on two questions: tracking down all the specific genes that may be involved in triggering the disorder; and relating Hashimoto disease to other autoimmune disorders that have a high female/male sex ratio. Some researchers think that there may be a common factor linking Hashimoto disease to

lupus, rheumatoid arthritis, and other autoimmune disorders that disproportionately affect women.

SEE ALSO Graves disease; Hypothyroidism

WORDS TO KNOW

Autoimmune disease: A disease in which the body's immune system attacks its own cells and tissues.

Goiter: A swelling in the neck caused by an enlarged thyroid gland.

Hashitoxicosis: A temporary phase in some patients with Hashimoto disease in which there is too much thyroid hormone in the blood due to leakage from damaged and dying cells in the thyroid gland.

Hyperthyroidism: A disease condition in which the thyroid gland produces too much thyroid hormone.

Hypothyroidism: A disease condition in which the thyroid gland does not produce enough thyroid hormone.

Levothyroxine: The chemical name for the synthetic thyroid hormone given to treat Hashimoto disease.

Metabolism: The chemical changes in living cells in which new materials are taken in and energy is provided for vital processes,

Thyroiditis: Inflammation of the thyroid gland.

For more information

BOOKS

Skugor, Mario. Thyroid Disorders: A Cleveland Clinic Guide. Cleveland, OH: Cleveland Clinic Press, 2006.

PERIODICALS

Angier, Natalie. “Researchers Piecing Together Autoimmune Disease Puzzle.” New York Times, June 19, 2001. Available online at http://query.nytimes.com/gst/fullpage.html?res=9502E3DD1031F93AA25755-C0A9679C8B63&sec=&spon=&pagewanted=all (accessed April 4, 2008).

Pérez-Peña, Richard. “Cases: Heeding Thyroid's Warnings.” New York Times, October 7, 2003. Available online at http://www.query.nytimes.com/gst/fullpage.html?res=980DE0D6133CF934A35753C1A9659C8B63 (accessed April 4, 2008).

WEB SITES

American Thyroid Association (ATA). Thyroiditis. http://www.thyroid.org/patients/patient_brochures/thyroiditis.html (accessed April 4, 2008).

Hormone Foundation. Hormones and You: Hashimoto's Disease. http://www.hormone.org/Resources/Thyroid/upload/Bilingual_Hashimotos_Disease.pdf (accessed April 4, 2008).

National Women's Health Information Center. Hashimoto's Thyroiditis. http://www.womenshealth.gov/faq/hashimoto.htm (accessed April 4, 2008).

Nemours Foundation. Thyroid Disorders. http://www.kidshealth.org/kid/health_problems/glandshoromones/thyroid.html (accessed April 4, 2008).