[Thyroid diagnosis today].

For functional diagnostics the FT4 index is calculated from the T4 and T3U values. Hyperthyroidism is suggested or borderline values are found; the T3 test is carried out. An index of free iodine hormones (IFIH) can be calculated. (formula; see text) Hypothyroidism and borderline cases require TSH evaluation or even a TRH test. T4 and T3 autoantibodies can cause high or low values in spite of euthyroidism or hypothyroidism. Differences in FT4 values are found if the kits used were not made by the same manufacturer. These values help to determine hyperthyroidism in pregnancy. The FT3 value is better than the TT3 value in determining T3 hyperthyroidism in borderline cases. Autonomy can be guaranteed by the 123 I short test or the 20-min 99 m Tc uptake test before and after administration of T4. Location diagnostics by scintigraphy after administration of 99m Tc or radioiodine determine localization, size, shape, and distribution of functioning thyroid tissue and metastases by iodine accumulation. This is imaging of biochemical processes. By ultrasonography, a physical method, cysts, disintegration cysts or parenchymal nodes can be recognized. X-ray films of the trachea can determine stenosis caused by a struma. In addition to the exact proof of an intrathoracal struma (front and back mediastine), a retrotracheal or retroesophageal thyroid gland can be seen on CT. RIA determination of the tumor markers calcitonin and TG supports the diagnosis of medullar and follicular or papillary thyroid carcinoma.