中枢性甲状腺機能低下症の診断におけるTRH負荷後のT3測定の有用性

概要

論文の詳細を見る
TRH tests (500 μg, i.v. bolus) were performed in 15 patients with various hypothalamic or pituitary disorders and in 6 control subjects. TSH (highly sensitive RIA) and T3 were measured before and 30, 60, 90 and 120 min. after TRH. In 8 out of 15 patients, low circulating thyroid hormone levels were observed, but their basal TSH levels were all in the normal range or even higher (0.8-5.5 μU/ml).Further, their integrated TSH responses (38 ± 21μU/ml) did not differ significantly from those of control group (35 ± 16μU/ml). Except for 2 cases with hypothalamic hypothyroidism, T3 increments after TRH were found consistently lower than 5 ng/dl in these hypothyroid patients. One of them revealed significant elevations of T3, T4 and thyroid 99m Tc-pertechnetate uptake after 5 I.U. × 2 i.m. bovine TSH. In 19 cases studied (2 cases with hypothalamic hypothyroidism were omitted), basal T3 levels were found to show quite a good correlation (r=0.738) with T3 increments after TRH. Therefore, TSH values by radioimmunoassay in hypothalamo-pituitary disorders were considered not relevant to be the levels of a real thyroid stimulator, or they seemed to contain biologically inactive moieties. In conclusion, measurement of the TSH level and even the TRH-TSH test were found unreliable in diagnosing central hypothyroidism, and the TRH-T3 test appeared to give quite useful diagnostic information.
日本内分泌学会の論文