[Reaction of autonomous and non-autonomous thyroid tissue to iodination blockers]

In the case of thyrostatic therapy of autonomous adenoma with iodinization blocker type drugs (here carbimazol), there is a relative increase of uptake of 99mTc-pertechnetate by the suppressed thyroid tissue before TSH becomes detectable by TRH testing (400 micrograms). As soon as endogenous TSH stimulation occurs (due to the decrease of thyroid hormone induced by the thyrostatic therapy), relatively more uptake of 99mTc-pertechnetate by the non-autonomous tissue is observed. 56 patients suspected of having autonomous thyroid adenoma were investigated. The activities in the regions of interest measured over autonomous and non-autonomous thyroid tissue before and after thyrostatic therapy were expressed in form of a double-ratio. 22 of the 56 patients were found to have an autonomous adenoma (double-ratio greater than or equal to 1.74). In 19 patients an adenoma was excluded with certainty (double-ratio less than or equal to 1.22). The remaining cases fell in-between and were difficult to classify. However, the gradual transition between the two groups so classified was harmonious. The different reactions of autonomous and non-autonomous thyroid tissue to thyrostatic therapy appear to be helpful in the differentiation between the two types of tissue.