tiroglobulina

Thyroglobulin is a large glycoprotein produced by the follicular cells of the thyroid gland. Its primary role is as a precursor for thyroid hormones, namely thyroxine (T4) and triiodothyronine (T3). Within the thyroid follicle, thyroglobulin serves as a storage medium for iodine, which is essential for thyroid hormone synthesis.

The synthesis of thyroglobulin begins with its production within the thyroid follicular cells. It is then secreted into the colloid, the central lumen of the thyroid follicle. Here, iodine atoms are incorporated into the thyroglobulin molecule through a process called iodination. Following iodination, two iodinated thyroglobulin molecules are coupled to form T4 and T3, which remain attached to the thyroglobulin until they are needed by the body.

When stimulated by thyroid-stimulating hormone (TSH) from the pituitary gland, the thyroid follicular cells reabsorb thyroglobulin from the colloid. Proteases within the cells then cleave the thyroglobulin, releasing T4 and T3. These hormones are then secreted into the bloodstream.

Thyroglobulin itself has limited biological activity and is not considered a thyroid hormone. However, measuring serum thyroglobulin levels can be useful in clinical practice. Elevated levels can indicate an overactive thyroid gland (hyperthyroidism) or thyroid cancer. Following thyroid surgery or radioactive iodine treatment for thyroid cancer, serum thyroglobulin levels are monitored as a marker for recurrence. A persistent or rising level may suggest that residual cancer cells are still producing thyroglobulin.