Thyroglobulin (TG) is a iodine-containing glycoprotein formed in the endoplasmic reticulum of thyrocytes and stored as colloid in thyroid follicles. TG consists of long chains with residuals of triiodothyronine (T3) and thyroxine (T4), from which the thyroid hormones T3 and T4 can be separated through stimulation by thyroid-stimulating hormone (TSH), if necessary.
In many thyroid diseases (e.g. Graves' disease, autonomous thyroid adenoma) an increased TG value is found. The determination of TG is therefore not suitable for screening in tumour diagnostics. However, it is useful for an early diagnosis of relapses and metastases during aftertreatment of differentiated thyroid carcinoma. Since TG originates exclusively from the thyroid parenchyma, it can be considered as a tumour marker after therapeutic resection of the thyroid tissue, which has a high diagnostic sensitivity and specificity.