Tiroperoxidáz

Tiroperoxidáz, often abbreviated as TPO, is an enzyme that plays a crucial role in the synthesis of thyroid hormones, namely thyroxine (T4) and triiodothyronine (T3). This enzyme is primarily found in the thyroid gland, embedded within the apical membrane of thyrocytes, the cells that make up the thyroid follicles. TPO is a member of the heme peroxidase superfamily.

The primary function of tiroperoxidáz is to catalyze two key steps in thyroid hormone production. First, it facilitates the iodination of tyrosine residues on a protein called thyroglobulin, which is secreted into the follicular lumen. This process attaches iodine atoms to the tyrosine residues. Second, TPO mediates the coupling of these iodinated tyrosine residues, forming the T4 and T3 hormones, which are then stored within the thyroglobulin molecule.

The activity of tiroperoxidáz is essential for normal thyroid function. Its absence or significant dysfunction leads to congenital hypothyroidism, a condition characterized by impaired thyroid hormone production. Autoantibodies against TPO are a common finding in autoimmune thyroid diseases such as Hashimoto's thyroiditis and Graves' disease, serving as important diagnostic markers. Inhibition of TPO is also the mechanism of action for certain antithyroid drugs used in the treatment of hyperthyroidism.