Thyroid cancer is cancer that develops from the tissues of the thyroid gland. Thyroid cancers are treated by removing the whole or part of thyroid gland. Thyroid surgeons or otolaryngologists are responsible for the surgical management of thyroid disease. PFOA exerts hormonal effects including alteration of thyroid hormone levels. Excessive production of the thyroid hormones is called hyperthyroidism. Treatment is with thyroid hormone replacement. Pregnancy leads to marked changes in thyroid hormone physiology. Thyroiditis (inflammation of the thyroid) can also cause hyperthyroidism. Both the thyroid and adrenal glands can be infiltrated. The primary pathway of thyroid hormone metabolism is through sequential deiodination. Iodine is essential in the synthesis of thyroid hormones. Unsaturated TBG increases with decreased levels of thyroid hormones. Calcitonin is a hormone secreted by the thyroid in humans. Iodine is needed in trace amounts for the production of thyroid hormones such as thyroxine. The thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland.