Juvenile hypothyroidism among two populations exposed to radioiodine

We found an epidemic of juvenile hypothyroidism among a population of self- defined "downwinders" living near the Hanford nuclear facility located in s outheast Washington State. The episode followed massive releases of I-131. Self-reported data on 60 cases of juvenile hypothyroidism (<20 years of age ) among a group of 801 Hanford downwinders are presented, as well as data c oncerning the thyroid status of approximately 160,000 children exposed to r adioiodine before 10 years of age as a result of the 26 April 1986 Chernoby l explosion in the former Soviet Union These children were residents of fiv e regions near Chernobyl. They were examined by standardized screening prot ocols over a period of 5 years from 1991 to 1996. They are a well-defined g roup of 10 samples. Fifty-st: cases of hypothyroidism were found among boys and 92 among girls. Body burdens of Cs-137 have been correlated with hypot hyroidism prevalence rates. On the other hand, the group of juvenile (<20 y ears of age) Hanford downwinders is nor a representative sample. Most of th e 77 cases of juvenile hypothyroidism in the Hanford group were diagnosed f rom 1945 to 1970. However, the ratio of reported cases to the county popula tion under 20 years of age is roughly correlated with officially estimated mean levels of cumulative thyroid I-131 uptake in these counties, providing evidence that juvenile hypothyroidism was associated with radioiodine expo sures. Because even subtle hypothyroidism may be of clinical significance i n childhood and can be treated, it may be useful to screen for the conditio n in populations exposed to radioiodine fallout. Although radiation exposur e is associated with hypothyroidism, its excess among fallout-exposed child ren has not been previously quantified.