Melmed S, Spira O, Gordon A, Gross J, Jorgensen E C, Hershman J M
Endocrinology. 1980 Oct;107(4):1050-4. doi: 10.1210/endo-107-4-1050.
The effect of 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) a nonhalogenated thyroid hormone analog, on plasma and pituitary TSH levels was studied in euthyroid and 5-day-thyroidectomized (T-5d) rats. The minimal dose of DIMIT which suppressed basal plasma TSH for a 24-h period was 5.3 micrograms/100 g BW in the euthyroid rats and 5.2 micrograms/100 g BW in the T-5d group. The equipotent doses of T3 were 1.0 and 1.5 micrograms/100 g BW, respectively. Thus, the apparent DIMIT to T3 molar ratio ranged from 6.6 in the hypothyroid to 10 in the euthyroid group. The suppression of TRH-induced TSH release in the euthyroid rats required a high dose of DIMIT (9.2 micrograms/100 g BW), resulting in a DIMIT to T3 molar ratio of 17. Time-course studies comparing the effects of equipotent doses of DIMIT and T3 on TSH release rates in euthyroid and T-5d rats have shown a maximal suppression by 3--24 h after the administration of both T3 and DIMIT. However, the recovery from the effect was slower after T3. TSH synthesis in the T-5d group was similarly suppressed by DIMIT and T3. DIMIT has significant thyromimetic activity in euthyroid and hypothyroid rats, as evidenced by the suppresion of TSH synthesis and release.
研究了非卤化甲状腺激素类似物3,5-二甲基-3'-异丙基-L-甲状腺素（DIMIT）对正常甲状腺和甲状腺切除5天（T-5d）大鼠血浆及垂体促甲状腺激素（TSH）水平的影响。在正常甲状腺大鼠中，能在24小时内抑制基础血浆TSH的DIMIT最小剂量为5.3微克/100克体重，在T-5d组中为5.2微克/100克体重。T3的等效剂量分别为1.0和1.5微克/100克体重。因此，在甲状腺功能减退组中，DIMIT与T3的表观摩尔比为6.6，在正常甲状腺组中为10。在正常甲状腺大鼠中，抑制促甲状腺激素释放激素（TRH）诱导的TSH释放需要高剂量的DIMIT（9.2微克/100克体重），导致DIMIT与T3的摩尔比为17。比较等效剂量的DIMIT和T3对正常甲状腺和T-5d大鼠TSH释放率影响的时间进程研究表明，给予T3和DIMIT后3-24小时抑制作用最大。然而，T3作用后的恢复较慢。DIMIT和T3同样抑制T-5d组中的TSH合成。DIMIT在正常甲状腺和甲状腺功能减退大鼠中具有显著的拟甲状腺活性，TSH合成和释放受到抑制证明了这一点。
