[The value of serum thyroglobulin determination in the after-care of patients with differentiated thyroid neoplasms].

Plasma thyroglobulin (Tg) was determined by radioimmunoassay in 219 patients with differentiated carcinoma of the thyroid gland after treatment by total thyreoidectomy and at least 2 131I therapies with a total of 170 mC. Of 145 patients without residual thyroid tissue and a negative whole body scan, 6 patients exhibited significant Tg levels. It remains unclear whether these individuals will develop recurrency later on. Of 23 patients with proven metastases, 14 had extremely high Tg concentrations of greater than 1000 ng/ml. In 6 cases Tg was between 20 and 280 ng/ml and in 3 individuals Tg levels below 10 ng/ml were measured. The reason for low Tg concentrations in some patients with proven metastases is unknown. At present plasma Tg measurements therefore cannot be recommended as substitution for whole body scanning. However, plasma Tg is an important additional parameter in the follow-up of patients with differentiated carcinoma of the thyroid.