Thyroid Research Thyroid Research Archive Thyroid Cancer

A rise in serum thyroglobulin after thyrotropin administration indicates the presence of tumor in patients with thyroid carcinoma

(November 2005)

The background of the study. Measurements of serum thyroglobulin (Tg) are now indispensable for the follow-up of patients with thyroid carcinoma. This study determined the course of patients with carcinoma in whom serum Tg was measured after stimulation by thyrotropin (TSH) several years earlier.

How the study was done. The study subjects were 107 patients with papillary or follicular carcinoma of the thyroid treated by surgery and radioactive iodine (I-131). An average of 7 years later, serum Tg was measured both basally during thyroxine (T4) therapy and 72 hours after the injection of recombinant human TSH (rhTSH). Among the 20 patients who had rhTSH-stimulated serum Tg values >2.0 ng/ml, persistent tumor was identified (and treated) in 9 and suspected in 2. All the patients were followed for an additional 5 years. They were considered free of disease at the end of follow-up if ultrasonography of the neck was negative and their basal serum Tg values were <0.5 ng/ml on two or more occasions or their stimulated serum Tg values (after either rhTSH stimulation or withdrawal of T4 and endogenous TSH stimulation) were <0.5 ng/ml on one or more occasions.

The results of the study. Follow-up data were available for 101 of the 107 patients (94 percent). At the end of the study, 94 percent of the patients had basal serum Tg values <0.5 ng/ml, and the values ranged from 0.9 to 6.2 ng/ml in 6 percent. Among 63 patients whose first stimulated serum Tg values were very low (≤0.5 ng/ml), all had low basal and stimulated serum Tg values and no evidence of tumor during follow-up. Among 18 patients whose first stimulated serum Tg values were 0.6 to 2.0 ng/ml, basal or stimulated serum Tg values during follow-up were very low in 13 and stimulated values were 0.7 to 3.4 ng/ml in 5; tumor was found only in the patient with the highest stimulated serum Tg value. Among 20 patients whose first rhTSH-stimulated serum Tg value was >2.0 ng/ml, 14 had stimulated values >2.0 ng/ml during follow-up. Persistent tumor was found or suspected initially in 9 and was found in 7 others during follow-up, but at last follow-up, 11 (55 percent) had no evidence of tumor.

The conclusions of the study. Patients with papillary or follicular thyroid carcinoma who have a stimulated serum Tg value (>2.0 ng/ml) after surgery and I-131 treatment are likely to have persistent tumor, but it may be difficult to detect.

The original article. Kloos RT, Mazzaferri EL. A single recombinant human thyrotropin-stimulated serum thyroglobulin measurement predicts differentiated thyroid carcinoma metastases three to five years later. J Clin Endocrinol Metab 2005;90:5047-57.