Hypothyroidism is a very common condition in which the body has insufficient thyroid hormone due to an underactive thyroid gland. Thyroid hormone controls metabolism, so having low thyroid hormone levels results in symptoms consistent with slowed metabolism such as weight gain and fatigue. The condition is more common in women, especially after age 50. As many as 1 in 10 women may have some degree of thyroid hormone insufficiency.
Causes of Hypothyroidism
The most common cause of hypothyroidism is an autoimmune disease, called Hashimoto thyroiditis, in which the immune system attacks cells of the thyroid gland. The resulting damaged cells are unable to produce thyroid hormone. The risk of developing hypothyroidism increases with age, and is also increased in people with close relatives who have an autoimmune disease. Other types of damage to the thyroid gland, either due to medications, radiation, or medical procedures, can also decrease thyroid hormone production. Hypothyroidism can also result from iodine deficiency, since iodine is needed to synthesize thyroid hormones, though this situation is rare in the U.S. since iodine is added to table salt.
Symptoms of Hypothyroidism
Thyroid hormones regulate many aspects of metabolism, including metabolic rate, body temperature, heart rate, and blood calcium levels. Symptoms of hypothyroidism are consistent with the resulting effects on metabolism. Not all people experience all symptoms, to the same degree or severity.
Hypothyroidism can cause fatigue, weakness, weight gain and increased cholesterol. In addition, it can result in dry skin, brittle nails, dry hair, and hair loss. People with hypothyroidism frequently feel cold. They may also experience memory loss, depression and irritability. In response to the lack of thyroid hormone, the body produces thyroid stimulating hormone, to induce the thyroid to produce more thyroid hormone. This can cause the thyroid to enlarge, forming a goiter. Symptoms generally worsen as the levels of thyroid hormone decrease. If untreated, hypothyroidism can lead to obesity and heart disease. In very rare cases of extreme hypothyroidism, called myxedema, coma and death can result.
Diagnosis and Treatment of Hypothyroidism
Hypothyroidism is diagnosed with a blood test to measure levels of thyroid stimulating hormone, a sensitive test that can detect changes in thyroid function before symptoms are apparent. If this hormone is elevated, it means the body is trying to induce the thyroid to produce more thyroid hormone. A thyroid hormone test can confirm hypothyroidism. Treatment is straightforward, involving taking additional thyroid hormone in pill form every day and regular monitoring thyroid hormone levels to insure the dosage is correct.
