An underactive thyroid gland results in hypothyroidism. Thyroid hormone replacement with levothyroxine treats hypothyroidism. BCE described hyperthyroidism, hypothyroidism and goitre. The symptoms are those of hyperthyroidism and hypothyroidism. The resulting hypothyroidism is treated with synthetic thyroid hormone. The resulting hypothyroidism is treated with synthetic thyroid hormones. Iodine deficiency is the most common cause of primary hypothyroidism and endemic goiter worldwide. Usually it is hypothyroidism, specifically Hashimoto's thyroiditis. Exposure to PCBs causes hearing loss and symptoms similar to hypothyroidism in rats. It may also occur in the setting of hyperparathyroidism, hypothyroidism, and Cushing syndrome. Of people with subclinical hypothyroidism, a proportion will develop overt hypothyroidism each year. There have been cases of compartment syndrome associated with hypothyroidism. It has also been reported as occurring in association with diabetes, hypothyroidism, and migraine attacks. All people with memory difficulty should be checked for hypothyroidism and B12 deficiency. Congenital hypothyroidism (CH) occurs in 1&colon;1300 to 1&colon;4000 births worldwide.