Hypothyroidism
(Hashimoto's Thyroiditis)
Definition |
Causes |
Risk Factors |
Symptoms |
Diagnosis |
Treatment |
Prevention |
Organizations
Definition
Hypothyroidism is a disease in which the thyroid gland does not produce enough thyroid hormone. The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. Hashimoto's thyroiditis is the most common cause of hypothyroidism.
Causes
Hashimoto's thyroiditis is an autoimmune disease. Your own immune system creates antibodies that attack the cells of the thyroid gland. This causes chronic thyroid inflammation and loss of thyroid function. Other causes of hypothyroidism include:
- Idiopathic thyroid atrophy – destruction of thyroid tissue for unknown reasons
- Iodine deficiency – when a thyroid gland needs iodine to produce thyroid hormone (rare in the United States)
- Subacute thyroiditis – following a viral upper respiratory tract infection
- Medical treatments – radiation or surgical removal of part of the thyroid gland (called subtotal thyroidectomy)
- Antithyroid drugs
- Pituitary adenoma – benign tumor of the pituitary gland
Risk Factors
A risk factor is something that increases your chance of getting a disease or condition.
- Age: risk increases with age
- Sex: Female
- Pregnancy – postpartum thyroiditis (first hyperthyroid, followed by hypothyroid)
- History of family members with hypothyroidism
- History of other autoimmune diseases:
- Pernicious anemia
- Diabetes
- Underactive adrenal or parathyroid glands
- Rheumatoid arthritis
- Lupus
Symptoms
Symptoms develop gradually, and may go unnoticed for years.
Early symptoms include:
- Enlargement of the thyroid gland (goiter) – not always present
- Fullness in the neck
- Difficulty swallowing (severe goiter)
Later symptoms (as hypothyroidism develops) include:
- Fatigue
- Weakness
- Coarse, brittle hair
- Dry skin
- Cold intolerance
- Weight gain
- Constipation
- Achy feeling all over
- Depression and irritability
- Memory loss
- Heavy menstrual periods
Symptoms of severe or prolonged cases include:
- Diffuse swelling of the skin and tissue around the eyes
- Slow heart rate
- Hypothermia (low body temperature)
- Hoarseness
Diagnosis
The doctor will ask about your symptoms and medical history, and perform a physical exam. The exam may reveal a goiter (enlarged thyroid). You will be given blood tests to measure thyroid hormone levels and to look for antibodies that attack the thyroid gland. In rare cases, a needle biopsy of the thyroid is needed. In a needle biopsy, a sample of thyroid tissue is removed with a needle and tested.
Treatment
In the early stages of Hashimoto's thyroiditis, there is no specific treatment. However, most people with Hashimoto's thyroiditis eventually develop hypothyroidism. At that point, you will need to start taking medication that replaces the thyroid hormone your thyroid is not producing. You will have to take this medication indefinitely.
Prevention
There are no guidelines for preventing this disease. If you think you might be at risk for Hashimoto's thyroiditis, speak with your doctor about an appropriate schedule of check-ups.
Organizations
American Thyroid Association
http://www.thyroid.org
SOURCES:
American Association of Clinical Endocrinologists
Harrison's Principles of Internal Medicine, 15th ed.McGraw Hill, 2001.
Last reviewed June 2001 by Medical Review Board
