抄録
Seventy-five TRH tests were carried out in 61 subjects with hyperthyroidism before and in the course of treatment; the results were correlated with serum T4 and T3 concentrations. In certain subjects, T3 suppression tests were done along with the TRH test. All subjects with elevated T4 and T3 (group 1) did not show a TSH response to TRH. Eleven out of 13 subjects with normal T4 and elevated T3 (group 2) did not show TSH response. In 22 subjects with normal T4 and T3 (group 3), 40.9%(9/22) did respond and 59.1%(13/22) did not respond to TRH. In 7 subjects with low T4 and/or T3 (group 4), 4 did not respond and 3 did respond to TRH. In each group, there were no significant differences in age and sex of the subjects, mode of therapy, serum thyroid hormones (T4, T3) and BMR between responders and non-responders to TRH. Sixteen subjects underwent T3 suppression tests. Twelve subjects with no or low TSH response to TRH did not show suppression, while all 4 subjects with normal or exaggerated TSH response showed suppression. The results indicate that serum thyroid hormone levels are not the sole determinant of the TSH response to TRH and confirm that the suppressibility of the thyroid gland by T3 appears to require the presence of sufficient TSH secretion from the pituitary. Several mechanisms of variable TSH response to TRH in the course of treatment of hyperthyroidism were discussed.
