The most common cause of hypothyroidism is an autoimmune disorder called Hashimoto's disease, named for the Japanese physician who first recognized it in 1912. In addition, five to eight percent of women develop hypothyroidism soon after giving birth. While this pregnancy-related condition is usually temporary and often doesn't require treatment, some new mothers may need to take thyroid hormone indefinitely. Whatever the cause, an underactive thyroid leaves the body running in slow motion. Changes may include fatigue, feeling cold, diminished concentration and memory, and weight gain.
Depression also results from hypothyroidism.
Up to 20 percent of all chronic-depression cases may be associated with low production of thyroid hormones. Often, unfortunately, patients who are treated for depression do not first get thyroid tests. Determining the right medication and dose, though, may require experimenting. Sometimes treatment for an underactive thyroid may even create the symptoms of hyperthyroidism and vice versa. A San Jose, Calif., woman was told she had Hashimoto's disease, and a synthetic thyroid hormone was prescribed.