Computed tomography of the thyroid vascular, encapsulated structure made up of right and left lobes, which are connected at the midline by the isthmus. Each lobe is about 2 cm thick, 3 cm wide, and 5 cm long. The thyroid apex is located superiorly at the level of the mid-thyroid cartilage. The inferior margin of the gland is at the level of the fifth or sixth tracheal ring. The thyroid gland is encapsulated by the middle layer of deep cervical fascia and is part of the visceral space in the infrahyoid neck. It wraps around the trachea and is separated from the oesophagus by the
Thyroid peroxidase Thyroid peroxidase Thyroid peroxidase, also called thyroperoxidase (TPO) or iodide peroxidase, is an enzyme expressed mainly in the thyroid where it is secreted into colloid. Thyroid peroxidase oxidizes iodide ions to form iodine atoms for addition onto tyrosine residues on thyroglobulin for the production of thyroxine (T) or triiodothyronine (T), the thyroid hormones. In humans, thyroperoxidase is encoded by the "TPO" gene. + I + H+ HO ⇒ + 2 HO Iodide is oxidized to iodine radical which immediately reacts with tyrosine. The second iodine atom is added in similar manner to the reaction intermediate 3-iodotyrosine. Inorganic iodine enters the