The thyroid gland is localized below the larynx, occupying the anterior and lateral space around the trachea. The most abundant hormone secreted by the thyroid is thyroxine or T₄ (approximately 93%), followed by triiodothyronine or T₃ (approximately 7%). These thyroid hormones are formed from thyroglobulin, which is synthesized in the endoplasmatic reticulum and in the Golgi apparatus, and stored into structures of the thyroid known as follicles. Each follicle is surrounded by capillary blood vessel, and it is constituted by epithelial cubical cells on the outside, containing a substance secreted by the gland termed colloid. These epithelial cubical cells have the ability of trapping iodides on their membranes, which are later enzymatically combined with thyroglobulin to form the thyroidal hormones inside the follicles. A weekly dietary intake of 1mg of iodine is essential for hormone synthesis by the thyroid. Iodine, mostly under the form...