[Follow-up studies of patients with negative TRH test and normal thyroid hormone levels]

The aim of the study was to assess the clinical significance of the association of a negative TRH-test with normal thyroid hormone levels. Therefore, we repeated the investigation in 63 patients one year after the first examination. In 6 patients (10%) hyperthyroidism had developed. Euthyroid autonomy was diagnosed in 11 patients (17%). A prolonged normalisation period of the pituitary-thyroid regulation after having discontinued the thyroid hormone drugs was found in 7 patients (11%). In 40% of the patients the TRH-test remained negative and in 22% of the patients the TSH-response became positive without any known reason. The findings show that a negative TRH-test and normal thyroid hormone levels do not necessarily imply subclinical hyperthyroidism.