Is serum thyroglobulin a useful marker for thyroid cancer in patients who have not had ablation of residual thyroid tissue?

Serum thyroglobulin has been measured sequentially in 47 patients with differentiated thyroid cancer who had been treated by surgery and I-thyroxine, but no radioiodine (I-131). In 39 of the patients, the operation was subtotal or total thyroidectomy, and in 8 patients it was lobectomy, or lobectomy plus isthmusectomy. In the first group of patients, serum thyroglobulin (Tg) was consistently undetectable in 62% and less than 5 ng/mL in 85%. In the latter group only 1 patient had undetectable Tg values and 2 (25%) had values less than 5 ng/mL. Even in those with higher Tg values, the levels remained constant within a narrow range, provided thyrotropin (TSH) was not high. Serum Tg can be used in conjunction with clinical evaluation in follow-up of patients with differentiated thyroid cancer who have had an operation consisting of more than lobectomy and isthmusectomy and have not been treated with I-131. Its use in patients with lesser operations has to be interpreted in relation to the amount of thyroid left and to the consistency of the results with time.