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Hypothyroidism, which occurs when an underactive thyroid does not produce enough hormones, can be a dangerous condition if untreated.

Instead of the bodily systems speeding up and overheating, they slow down in a variety of ways. This thyroid disease's symptoms include the following:


Mental depression


Feeling cold

Weight gain

Dry skin and hair


Menstrual irregularities

NOTE: The most severe expression of hypothyroidism may be referred to as myxedema. If you have severe hypothyroidism, a significant injury, infection, or exposure to cold or certain medications may trigger a life-threatening condition called myxedema coma. This condition may cause a patient to lose consciousness and to develop hypothermia, a life-threatening low body temperature.


Hashimoto's Hashimoto's disease is the most common cause of hypothyroidism in the United States. It occurs when the immune system produces antibodies that attack the thyroid gland, creating chronic inflammation that damages the gland and interferes with its ability to make enough thyroid hormone. It occurs more often in women than men, and tends to run in families.

Hypothyroidism can be traced to several other conditions as well, including:

Subacute, lymphocytic, or postpartum thyroiditis. These inflammations of the thyroid gland often start as hyperthyroidism, as stored thyroid hormone leaks out of the gland and raises hormone levels in the blood. Most people then develop temporary or, very rarely, permanent hypothyriodism.

Drugs that affect thyroid function, such as amiodarone, which is used to treat heart rhythm abnormalities.

A pituitary gland that does not make enough thyroid-stimulating hormone (TSH).

Treatment for hyperthyroidism (too much thyroid hormone) with radioactive iodine or surgery.

Routine testing of babies at birth identifies any with congenital hypothyroidism, a condition in which the thyroid gland has not developed properly. This testing is essential for all newborns, because if hypothyroidism in not treated, a child could experience mental slowness or retardation, or fail to grow normallly. Hypothyroidism during pregnancy can also negatively affect the baby. Experts have not yet reached a consensus as to whether all pregnant women should be routinely screened for thyroid hormone deficiency.

Hypothyroidism is increasingly common as we age. Women over 50 should consider being screened for thyroid deficiency every few years. Hypothyroidism affects as many as 15 percent of women over 70 years of age.


Hypothyroidism is treated by replacing the thyroid hormone the body needs. This is usually done with an oral tablet or pill of the thyroid hormone thyroxine (T4 or levothyroxine). A person will usually notice an improvement in his or her health and decreased symptoms of thyroid disease within two weeks. Severe cases of hypothyroidism, however, may take longer to correct. Most patients with hypothyroidism will need to be on T4 treatment for the rest of their lives. They have to work closely with their doctor, take their medication as directed, and be monitored regularly in case the medication dose needs to be adjusted. If patients take too much T4, they can develop a mild case of hyperthyroidism. If they do not get enough, the symptoms of hypothyroidism will return.

A patient may need special attention if in addition to suffering from thyroid problems, he or she is:

Older or has a weak heart. Thyroid hormone can make the heart work harder. A lower dose may be needed.

Pregnant. Higher doses may be needed during pregnancy. Frequent monitoring is required during this time, too, because the thyroid hormone dosage may change. An adjustment in dosage may be necessary after delivering the baby as well.

Having surgery. A person should have enough T4 in his or her system before surgery to undergo the anesthesia and have a satisfactory recovery. If an individual is unable to take medicine by mouth, T4 can be given intravenously after surgery. A diagnosis of hypothyroidism is especially important in pregnancy to ensure the delivery of a healthy baby.

© 2012 The Hormone Foundation. All rights reserved.


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