Thyroglobulin and anTi-Thyroglobulin: role in Thyroid disease TesTing
Thyroglobulin (Tg) is a glycoprotein synthesized by the thyrocytes and plays a key role in the synthesis of thyroid hormones, T3 and T4. Its production is stimulated by TSH, intrathyroidal iodine deficiency and the presence of thyroid-stimulating immunoglobulins.
The American Thyroid Association published a number of recommendations for management of patients with thyroid nodules and differentiated thyroid cancer. The recommendations for diagnostic testing follow1:
- Routine measurement of serum Tg for initial evaluation of thyroid nodules is not recommended.
- Routine preoperative measurement of serum Tg is not recommended. [NOTE: This refers to the removal of the primary thyroid tumor in differentiated thyroid cancer (DTC)].
- Postoperatively, serum Tg should be measured every 6-12 months by an immunometric assay that is calibrated against the CRM-457 standard. Ideally, serum Tg should be consistently assessed in the same laboratory and using the same assay, during follow-up of patients with DTC who have undergone total or near total thyroidectomy with or without thyroid remnant ablation.
- Thyroglobulin antibodies (anti-Tg) should be quantitatively assessed with every measurement of serum Tg.