INTRAVENOUS AND PERORAL TRH STIMULATION IN SPORADIC ATOXIC GOITRE

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Abstract
Thyrotropin releasing hormone (TRH) stimulation test with 200 .mu.g i.v. was performed in 35 patients with atoxic sporadic goiter. In 23 patients with diffuse goiter 7 showed a lack of increase in serum thyrotropin (TSH) at a significantly increased frequency compared to controls (P = 0.0028). In 4 patients with solitary nodules 2 showed no significant response to TRH (negative), while 3 of the 8 patients with multinodular goiters had negative TRH test. Only 6 of the 12 TRH negative patients also had non-suppressible 131I uptake following T3 [triiodothyronine]. No significant difference in age and thyroid parameters was found between the TRH negative and TRH positive patients. In 7 TRH negative patients the test was repeated with 400 .mu.g TRH but all remained negative. Five of these patients were given TRH perorally 80 mg daily for 2 wk resulting in a significant increase in serum T4 [thyroxine] and T3. No detectable increase in TSH was found. The response to i.v. bovine TSH in 4 TRH negative patients was found to be normal, suggesting that there was normal thyroid sensitivity to TSH. The findings suggest that patients with TRH negative atoxic goiter can release biologically active TSH following prolonged TRH stimulation. The high frequency of a negative standard TRH test in atoxic goiter seems to diminish the diagnostic value of the standard TRH test.

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