In order to find out the influence of surgical operation on the thyroid endocrine functionin the newbons, the levels of serum T,, T4 and rT, of 30 newbrons who received surgerywere determined before and after operations by radioimmunoassay. The results of this studyshowed that the postoperative levels of T3 and T4 reduced significantly (P<0.01), while thepostoperative levei of r, increased obviously (P<0. 01 ). All changes of postoperative thy-roid hormone returned to normal in about 7 days. At the same time, it was found that a per-sistent low level of T’ after operation indicated a poor prognosis and 3ignificant low level ofT, indicated a 8erious illness ; and there was a hlgh mortality (67% ) if the leveI of T’ was be-low 65ng/ml and the level of T, was below o. 5ng/ml. This study suggests that the determi-nations of T, and T’ indicate seriousness and forcast the progno8is of patients who received
