抄録
There have been very few, and some conflicting reports concerning the effects of ACTH and adrenocortical steroids on the peripheral metabolism of thyroxine.
At first, the turnover rate of I131-thyroxine (I131-T4 T.R.) and the thyroxine-binding capacity (TBC) were studied in normal subjects, in patients with treated hyperthyroidism (clinically maintained in normal state), untreated hyperthyroidism and hypothyroidism.
Secondly, the I131-T4 T.R. and the radioactivity in the urine and feces were studied in patients in various thyroid states for 7 to 10 days. Then these values were determined during the 5 days' administration of large doses of ACTH and adrenocortical steroids in the same patients. In addition, the changes of PBI and TBC were compared before and after the administration of the drugs.
The following results were obtained :
1) The average of the I131-T4 T.R. was 10.67%/day in the normal group, 11.34%/day in the treated hyperthyroid group which does not significantly differ from that of normal subjects, whereas the hyperthyroid group showed a high value of 19.78%/day and the hypothyroid group a low value of 8.15%/day, indicating a significant difference from that of the normal group. Furthermore, the interrelation between the I131-T4 T.R. and other thyroid function tests was as follows ; the correlation coefficient with BMR was + 0.747, with I131 thyroidal uptake + 0.514 and with PBI + 0.877.
2) The average value of TBC was 19.2γr/dl in the normal group, 17.9γ/dl in the treated hyperthyroid group which does not significantly differ from that of the normal group, whereas the hyperthyroid group showed a low value of 10.2γ/di, the hypothyroid group a high value of 31.9γ/dl. This indicates that there is a significant difference between the value of TBC of the normal group and that of the hyperthyroid or the hypothyroid group. In addition, the interrelation between TBC and other thyroid function tests was as follows : the correlation coefficient with BMR -0.627, with I131 thyroidal uptake -0.593, with PBI -0.760.
3) The I131-T4 T.R. increased in all patients treated with 160 units of ACTH, 30 mg of prednisolone or 2 mg of dexamethasone daily. Also the significant increases were observed statistically in five out of seven patients treated with 300 mg of hydrocortisone daily, while no significant changes were observed in patients given 120 mg or 180 mg.4) The urinary excretion rate of I131 showed a highly significant increase during the administration of ACTH or dexamethasone. In five out of seven patients treated with 300 mg of hydrocortisone daily, significant increases were observed. These increases in the urinary excretion rate of I131 were observed only in patients with an increase in the 131-T4T.R. The urinary excretion rate of BEI131 (butanol extractable radioiodine) ranged between 2.4% and 5.1% of total urinary I131, and showed no significant increase during the administration of ACTH or adrenocortical steroids. The fecal excretion rate of I131 remained unchanged during the administration of ACTH or adrenocortical steroids.
These results indicate that the excretion of I131 increased only into the urine in the form of free radioiodide.
5) A significant decrease in the PBI was observed after the administration of large doses of ACTH or hydrocortisone for 5 days. No significant change was obtained after the administration of 2 mg of dexamethasone for 5 days, but the administration of the same doses for 14 days induced a decrease in PBI significantly.
6) A significant decrease in TBC of serum was observed after the administration of 160 units of ACTH, 300 mg of hydrocortisone or 2 mg of dexamethasone for 5 days. In vitro, however,
