[Standardisation of TRH test for the exact determination of thyroxine treatment (author's transl)].

A TRH test was performed on 50 patients treated on a daily thyroxine dose of 50-200 microgram. Results were compared with a test performed at the earliest three weeks on the same thyroxine dosage, but the latter having been interrupted for 24 hours. In the first case T4 was 8.96 +/- 2.9 microgram/dl, in the second 7.08 +/- 2.0 microgram/dl; T3 in the first case 1.28 +/- 0.3 ng/ml, in the second 1.03 +/- 0.25 ng/ml. This indicates that with both thyroid hormones the levels were higher on the day of administration than 24 hours later. Correspondingly, TRH-stimulated TSH secretion was definitely lower on the day of treatment. delta TSH (TSH after 30 minutes minus TSH zero value) was 16.1 +/- 26.5 on day of treatment, 27.3 +/- 35.6 micro U/ml after pause. Accordingly, to achieve "fine tuning" of T4 treatment, such as for euthyroid goitre, the TRH tests standardised on 200 microgram TRH should be performed after a T4-free 24-hour interval. delta TSH should then not be more regimen, drug-induced hyperthyroidism can be definitely avoided.