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.
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