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THE INCIDENCE OF CONGENITAL HYPOTHYROIDISM AMONG IMMIGRANTS. 530

The incidence of congenital hypothyroidism (CH) has been shown to vary among different parts of the world. This could result from environmental or hereditary factors. Studies of other congenital diseases have shown that immigrants tend to retain the incidence of their country of origin while their children acquire the incidence of their new homeland, suggesting an environmental influence. This study aimed to assess the differences in the incidence of CH among immigrants from different parts of the world as well as to study the effects of the immigration on its occurrence. During the 9 year period between 1979 and 1987, 283 primary CH infants were born in Israel which constitute an incidence of 1:3078 live births. We collected data from hospitals, endocrine pediatric clinics and the children's parents regarding the birth place of the parents born in Israel and those of immigrants of the same origin. CH incidence was lower among offspring of mothers of Israeli, European and American origin and higher among those of African mothers and Asian fathers. Both mothers and fathers born in Israel, of Asian and African origin, had a lower incidence of CH affected children compared to parents of the same origin born in their continent of origin. This trend was reversed for European and American parents for whom being born in Israel was related to an increase in the CH incidence in their children. The difference in CH incidence between offspring of Israeli-born parent and those of non-Israeli born parents, of the same origin, was statistically significant. There was no significant difference in CH incidence between offspring of mothers compared to offspring of fathers of the same origin. In conclusion, environmental changes resulting from immigration can influence the incidence of congenital hypothyroidism.