抄録
Researches were made on the swelling of the thyroid gland among school children, 380 boys and 273 girls of a country village: Masutomi in Yamanashi Prefecture, where strongly radioactive springs issue, and further 3182 boys and 4547 girls in the control district: Namely Tadao Village near Tokyo, Tokyo City, Usuda Town in Nagano Prefecture, and Funabashi City in Chiba Prefecture. The thyroid enlargement was classified into 5 grades according to a modified Dieterle's method.
The investigation revealed that the children in the radioactive spring area have more enlarged thyroid gland than those in the other district.
The content of Radon in the ground waters of Masutomi Village ranged from 1.31×10-10C/l to 103×10-10C/l, 19.59×10-10C/l in an average, but Radon content of the ground waters in the other district proved mostly less than 4×10-10C/l. The thyroid function was investigated in 13 school children of Masutomi Village who showed thyroid swelling of Grade II-III.
(1) Examination of basal metabolic rate revealed in increase over 20% in 5 of 13 cases. The highest values recorded +24%.
The lowest being -5.8%, +11.8% on an average.
Eight cases showed normal values.
(2) P. B. I.: Eleven cases out of 13 cases showed higher values than 8γ/100ml. P. B. I. ranged from 7.5 to 12.6γ/100ml, 9.6γ/100ml on an average.
(3) Plasme I131 Conversion rate: Eight cases out of 13 cases showed higher values than 45%, and remaining 5 cases proved normal. The highest value being 65.5%, the lowest 15.5%, average 44.8%.
Therefore the above-mentioned enlargement of the thyroid gland in school-children living in radioactive spring district did not correspond to a hypofunction of the gland, hot it coincides rather with an increase in the thyroidal function.
Akisada measured iodine and calcium content in the ground waters of Masutomi, but neither deficiency of iodine nor excess of calcium were proved.
Seo and Akisada administered to rabbits daily 10ml per kg body weight of a radioactive water of Masutomi (Rn: 8363×10C/l) with stomach tube for 150 days.
They found a hyperplasia in the thyroid gland histologically but no pathological signs were found in the other organs.
