CLINICAL STUDY ON THYROID FUNCTION WITH RADIOIODINE

1 THE THYROIDAL METABOLISM OF I¹³¹

Abstract

The thyroidal uptake of radioiodine was observed after oral administration of I¹³¹ for 72hours.In hyperthyroidism, the maximum uptake was botained at 3 or 6 hours after I¹³¹ administration and I¹³¹in thyroid decreased at 24 hours, after I¹³¹adrninistration.
In simple goiter, this phenomenon was not observed and the peak of the thyroidal uptake was seen at 24 hours.
The uptake was higher in hyperthyroidism than in simple goiter (higher than 30% at 1 hour, higher than 45% at 24 hours), and in hypothyroidism, the uptake was always lower than 10%.But the high uptake was observed in a few cases of simple goiter.
At early time (1 or 3 hours after administration of I¹³¹), the blood level of I¹³¹was higher in simple goiter than in hyperthyroidism, but in the latter, plasma I¹³¹ level decreased again 24hours after I¹³¹ administration.
This phenomenon was not observed in the former.
Thus the Blondal index (PI¹³¹ at 48 hours/PI¹³¹ at 2 hours) noticed no overlapping.
The protein bounded I¹³¹ increased also after 24 hours in hyperthyroidism and the conversion ratio to protein bounded I¹³¹ was higher than in simple goiter.
The metabolism of I¹³¹ in hyperthyroidism was changed by phenobarbital medication and resembled the type of simple goiter.
By the treatment with methylthiouracil etc, I¹³¹ metabolism was normalized, but after improvement of I¹³¹ metabolism, a few relapse was occured.