Thyroid disease in women tests. The thyroid is a small gland in the front of the neck. The thyroid makes hormones called T3 and T4 that regulate how the body uses energy. Thyroid hormone levels are controlled by the pituitary gland, which is a pea-sized gland in the brain. It makes thyroid stimulating hormone (TSH), which triggers the thyroid to make thyroid hormone. In thyroid disease the immune system makes antibodies that damage thyroid cells and interfere with their ability to make thyroid hormone. Over time, thyroid damage can cause thyroid hormone levels to be too low. This is called an underactive thyroid or
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