Thyroglobulin is a ~660kD homodimer produced by the thyroid gland, specifically in the thyrocytes, and stored within the follicular lumen. Thyroglobulin is the precursor of the iodated thyroid hormones thyroxine (T4) and triiodothyronine (T3). These hormones affect protein, fat and carbohydrate metabolism. Defects in thyroglobulin production can lead to goiter, and increased susceptibility to autoimmune thyroid type 3 diseases, such as Graves disease and Hashimoto thyroiditis.