Thyroglobulin

Specimen:

5 mL blood in plain tube.

Method:

Immunoassay.

Reference Interval:

Laboratory dependent usually between <30 and <40 µg/L. Thyroglobulin (Tg) should be undetectable in a patient who has had a total thyroidectomy.

Application:

Detection of tumour recurrence in thyroid cancer.

Investigation of suspected thyroiditis or thyrotoxicosis factitia. Thyroglobulin antibody (Tg Ab) should be measured every time Tg is measured as the former may cause false negative results with Tg assays. 

Interpretation:

Detectable levels in patients with thyroid cancer who have had a total thyroidectomy (and who should cease thyroid replacement therapy for 2 weeks prior to testing) indicates the presence of residual tumour.

Stimulation with recombinant TSH prior to testing has been recommended with conventional Tg assays. Highly sensitive assays may obviate the need for TSH stimulation. Levels in thyroiditis and thyrotoxicosis are high, but if thyrotoxicosis is due to self-medication with thyroid hormone, the level is suppressed.

Reference:

Mazzaferri EL et al. J Clin Endocrinol Metab. 2003; 88(4): 1433-1441.

Spencer C et al. Curr Opin Endocrinol Diabetes Obes. 2014; 21(5): 394-404.