[Critical evaluation and rational use of nuclear medical techniques in the diagnosis of thyroid function (author's transl)].

The diagnosis of thyroid function has been decisively improved by the in-vitro tests and the radioimmunologic assays of total tri-iodothyronine- and TSH levels before and after stimulation with TRH. The high specificity and value of in-vitro tests lies in the quantitative measurement of peripheral hormoneconcentrations. The radio-iodine test, however, is only a qualitative technique giving information on movements of intrathyreoid radio iodine. The in-vitro tests are not falsified by iodine contamination. Extrathyreoidal protein-changes can be excluded with the ETR test. The radio-iodine test will now have to be done only in rare special cases. As a rule thyroid metabolism can be assessed safely by combining clinical examination with an in-vitro testblock adapted to the individual diagnostic problem with additional technetium scintigraphy.