Hypothyroidism occurs when too little thyroid hormone is produced. The thyroid controls the body's metabolism. This condition can slow down many of the body's functions. With treatment, hypothyroidism can be managed. However, when left untreated, it can have damaging effects on the body. Extreme cases can lead to myxedema. This causes the body's functions to slow down to the point of being life threatening. If this occurs, medical treatment should be sought immediately.