Circulating Thyroglobulin and Thyroid Hormones in Patients with Metastases of Differentiated Thyroid Carcinoma: Relationship to Serum Thyrotropin Levels

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Abstract
Twenty-six patients with metastases of differentiated thyroid carcinoma werestudied after total thyroid ablation. After T3 withdrawal, serum TSH, T4) and T3 were measured in all patients, thyroglobulin (Tg) was determinedin 11 patients, and rT3 was measured in 16 patients. Group 1 included 19 patients with radioiodine uptake in their metastases. The time course of change in serum TSHdiffered from patient to patient, ranging on the 10th day from 14–245 µU/ml and reaching a maximal value of 22–360 µU/ml. Tg levels increased in the 8 patients of this group who were studied and reached a plateau ranging from2.3–20 times its initial value. This increase was significantly correlated withtheserum TSH plateau level (r = 0.88; P < 0.01). T3 became detectable in only 3 cases, and T4 was detectable in only one of these 3 cases; rT3 reached the limit of detectability only in this case. Group 2 included seven patients without radioiodine uptake in the metastases. The timecourse of change in serum TSH levels and maximal TSH values were not different from thoseof the former group. Serum T3 and T4 remained undetectable, and theserum Tg level increased 1.7–2.8 times above its initial value in the three patients of this group who were studied. In one additional case in this group, TSH and Tg levels fell simultaneously under replacement therapy. Prolonged TSH stimulation increased Tg production in all patients studied even when there was no radioiodine uptake in the metastases. A T3, T4 or Tg feedback effect on the pituitary cannot explain the variability in TSH response after T3 withdrawal. Age appeared to be the only factor significantly correlated with the TSH plateau level (r = −0.75; P < 0.01). {J Clin Endocrinol Metab51: 513, 1980