According to the NIH, hypothyroidism affects about 5 percent of the U.S. population and women are more likely to develop it than men. The disease more commonly affects people over age 60.
Factors that may increase your chance of developing hypothyroidism include a personal or family history of thyroid disorders; another autoimmune disease (including Sjögren’s syndrome, pernicious anemia, type 1 diabetes, rheumatoid arthritis, or lupus); Turner syndrome (a genetic disorder that affects girls and women); or age older than 60 years. As well, women who have been pregnant or delivered a baby within the past six months and individuals who have received radiation to the thyroid or to the neck or chest may be at higher risk.
Causes of hypothyroidism include:
- Hashimoto’s disease (also called chronic lymphocytic thyroiditis)—an autoimmune disorder where antibodies attack cells in the thyroid and interfere with their ability to make thyroid hormone
- Thyroiditis—inflammation of the thyroid gland which causes stored thyroid hormone to leak and raise hormone levels in the blood
- Congenital hypothyroidism—hypothyroidism that is present at birth
- Surgical removal of part or all of the thyroid gland—may be performed for treatment of hyperthyroidism, a large goiter, thyroid nodules, or thyroid cancer
- Radiation treatment of the thyroid—destruction of cells of the thyroid to treat hyperthyroidism; radiation to head and neck for conditions such as Hodgkin’s and other lymphomas and cancers of the head and neck can also damage the thyroid
- Some medications
Symptoms of hypothyroidism include:
- Weight gain
- Puffy face
- Cold intolerance
- Joint and muscle pain
- Dry, thinning hair
- Decreased sweating
- Heavy or irregular menstrual periods and impaired fertility
- Slowed heart rate
People with high cholesterol should also be tested for hypothyroidism, as this thyroid disorder can contribute to high blood cholesterol.
To diagnose hypothyroidism, a doctor will likely discuss a patient’s symptoms and perform a physical examination. If he or she finds reason to suspect hypothyroidism, several tests may be used to confirm a diagnosis. Tests may also help determine the cause of the condition.
Tests for diagnosing hypothyroidism include:
Thyroid-stimulating Hormone (TSH) Test
This test detects small amounts of TSH in the blood to measure thyroid activity. When there is too much thyroid hormone in the blood, the pituitary gland stops producing TSH. In general, a TSH level reading below normal indicates hyperthyroidism and a reading above normal indicates hypothyroidism.
This test measures the amount of thyroid hormone circulating in the blood. In hypothyroidism, the level of T4 in the blood is below normal.
The Thyroid Autoantibody Test
The presence of thyroid autoantibodies suggests that Hashimoto’s disease is the cause of hypothyroidism (other causes are not associated with autoantibodies).
People with hypothyroidism are treated with synthetic thyroxine, a substance that is identical to the T4 made by the thyroid. Dosage will depend on the patient’s age and weight, severity of hypothyroidism, the presence of other health problems, and whether they are taking other medications that might interfere with how well the body uses thyroid hormone.
Pregnancy and Hypothyroidism
Uncontrolled hypothyroidism can increase the chance of certain complications among pregnant women. These include miscarriage, preterm delivery, and preeclampsia (a potentially serious complication that increases blood pressure). As well, untreated hypothyroidism can affect the baby’s growth and brain development. It’s important that pregnant women with hypothyroidism discuss the condition with their doctor—medications that are safe to take during pregnancy can help control hypothyroidism and prevent these complications.