thyroperoxidase

Thyroperoxidase, also known as thyroid peroxidase (TPO), is an enzyme that plays a crucial role in the synthesis of thyroid hormones. It is a member of the peroxidase family of enzymes and is found in the thyroid gland. TPO catalyzes the oxidation of iodide ions to form iodine radicals, which are then used to synthesize thyroid hormones, including thyroxine (T4) and triiodothyronine (T3). This process is essential for the regulation of metabolism, growth, and development in the body.

Thyroperoxidase is a heterodimeric protein consisting of two subunits, alpha and beta. The alpha subunit is responsible for the catalytic activity, while the beta subunit provides structural stability and is involved in the regulation of TPO activity. TPO is anchored to the thyroid follicular membrane and is associated with thyroglobulin, a glycoprotein that stores and releases thyroid hormones.

Thyroid peroxidase is a target of autoimmune antibodies in Hashimoto's thyroiditis, an autoimmune disorder that leads to hypothyroidism. The presence of anti-thyroid peroxidase antibodies is a diagnostic marker for Hashimoto's thyroiditis and is used to monitor the disease activity and response to treatment. TPO is also a target of autoantibodies in other autoimmune thyroid diseases, such as Graves' disease and thyroiditis associated with other autoimmune disorders.

The regulation of TPO activity is complex and involves multiple factors, including thyroid-stimulating hormone (TSH), thyroid hormone levels, and various cytokines and growth factors. TPO activity is increased in response to TSH and decreased in response to high levels of thyroid hormones. The regulation of TPO activity is crucial for maintaining the balance of thyroid hormone synthesis and release, which is essential for normal physiological function.