Undetectable Serum Thyroglobulin in a Patient With Metastatic Follicular Thyroid Cancer

The case of a 54-year-old woman with metastatic follicular thyroid cancer and undetectable serum thyroglobulin is presented. Many years after the patient had a subtotal thyroidectomy for a large goiter that had no clear evidence of malignancy, metastatic bone disease developed. When the bone metastases were detected and during the follow-up period, serum thyroglobulin values remained undetectable, but radioiodine uptake in the metastases was abundant. This case indicates that the combination of I-131 scintigraphy and serum thyroglobulin values is superior to the measurement of serum thyroglobulin alone in detecting well-differentiated, metastatic thyroid cancer.