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.