Thyroglobulin Monitoring After Thyroid Cancer Ablation
CC BY-SA 3.0 · Bionerd / Wikimedia Commons · source file
Question
After total thyroidectomy and I-131 remnant ablation for papillary thyroid cancer, follow-up includes serial serum thyroglobulin (Tg) measurement. The MOST important reason to measure Tg in thyroid cancer surveillance is:
- ATg levels predict post-ablative radioiodine uptake percentage by reflecting residual follicular cell mass via TSH receptor-mediated iodide organification capacity
- BElevated Tg after total thyroidectomy and ablation is a sensitive marker for residual or recurrent differentiated thyroid cancer
- CTg levels correlate directly with TSH levels through pituitary-thyroid axis feedback, serving as a proxy biomarker for inadequate TSH suppression therapy
- DTg measurement combined with anti-Tg antibody titers can replace all cross-sectional and functional imaging in long-term thyroid cancer surveillance protocols
Show the answer and explanation
B. Elevated Tg after total thyroidectomy and ablation is a sensitive marker for residual or recurrent differentiated thyroid cancer
Thyroglobulin (Tg) is a glycoprotein produced ONLY by thyroid follicular cells (normal or malignant). After total thyroidectomy and I-131 ablation, serum Tg should be undetectable in the absence of residual or recurrent disease. Any detectable Tg (especially stimulated Tg measured after TSH stimulation with thyroid hormone withdrawal or Thyrogen) is a sensitive marker for persistent or recurrent differentiated thyroid cancer. Stimulated Tg >1 ng/mL typically warrants further imaging (diagnostic WBS, neck ultrasound, FDG PET/CT for Tg-positive/scan-negative disease). Anti-Tg antibodies can interfere with Tg assays and must always be measured concurrently.
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