Hypothyroidism is a condition in which the body lacks sufficient thyroid hormone. Since the main purpose of thyroid hormone is to "run the body's metabolism", it is understandable that people with this condition will have symptoms associated with a slow metabolism. Over five million Americans have this common medical condition. Ten percent of women may have some degree of thyroid hormone deficiency.
There are two fairly common causes of hypothyroidism. The first is a result of previous (or currently ongoing) inflammation of the thyroid gland which leaves a large percentage of the cells of the thyroid damaged (or dead) and incapable of producing sufficient hormone. The most common cause of thyroid gland failure is called autoimmune thyroiditis (also called Hashimoto's thyroiditis), a form of thyroid inflammation caused by the patient's own immune system. The second major cause is the broad category of "medical treatments". As noted on a number of our other pages, the treatment of many thyroid conditions warrant surgical removal of a portion or all of the thyroid gland.
If the total mass of thyroid producing cells left within the body is not enough to meet the needs of the body, the patient will develop hypothyroidism. Remember, this is often the goal of the surgery as seen in surgery for thyroid cancer. But at other times, the surgery will be to remove a worrisome nodule, leaving half of the thyroid in the neck undisturbed.
Sometimes (often), this remaining thyroid lobe and isthmus will produce enough hormone to meet the demands of the body. For other patients, however, it may become apparent years later that the remaining thyroid just can't quite keep up with demand. Similarly, goiters and some other thyroid conditions can be treated with radioactive iodine therapy. The aim of the radioactive iodine therapy (for benign conditions)...