Thyroglobulin measurement in differentiated thyroid carcinoma management.

Differentiated thyroid cancer (DTC) is a rare disease with a generally good prognosis. The initial treatment is total thyroidectomy with ablation of thyroid remnants by iodine-131 (I). Currently, serum thyroglobulin (Tg) measurement and neck high-resolution ultrasound are the basis of follow-up. The thyroid cells are the only source of Tg in the human body, therefore, the presence of Tg after total thyroidectomy and ablative I therapy indicates persistence or recurrence of DTC. The sensitivity of Tg measurements can be optimized by clinical and technical improvements. Clinically, measurements of thyroid-stimulating hormone (TSH)-stimulated Tg after thyroid hormone withdrawal, or exogenous TSH administration in patients with undetectable serum Tg during thyroid hormone-suppression therapy, is recommended for revealing occult disease. Technically, the development of Tg assays with improved functional sensitivity enhances the value of Tg measurements, allowing us to measure Tg without any TSH stimulation during DTC with high negative predictive value. In particular, increasing serum Tg concentrations in highly sensitive assays are early and reliable indicators of recurrent disease. Several imaging methods are available for the localization of recurrences and metastases (i.e., I whole-body scan for iodine-positive metastases and fluorodeoxyglucose-PET or PET/CT scans for iodine-negative ones), but their rational use should be dictated by Tg testing results. This will be realized in a limited follow-up protocol, warranting the detection of recurrences of DTC and reducing patient burden and medical costs.