As people get older, their bones lose calcium and become less dense. When this bone thinning becomes severe, it is called osteoporosis. Persons with osteoporosis are at high risk for broken bones (fractures). Many older women have osteoporosis. Some older women also have problems with the thyroid gland, a gland located in the neck that makes thyroid hormone. Thyroid hormone is important in regulating the body's metabolism, particularly its use of energy, fats, and protein. Several past studies have examined whether high levels of thyroid hormone lead to osteoporosis. Results of these studies have been confusing, and few have looked at whether women with high levels of thyroid hormone actually have more fractures than women with normal thyroid hormone levels.