The increased incidence of thyrotoxicosis in immigrants.

Evidence is presented that, in Toronto, hyperthyroidism is significantly more prevalent in immigrants than in native-born patients. In a series of 4000 outpatients only eight of 1854 native-born patients were thyrotoxic, whereas 33 of 2146 immigrants proved to be so (p < 0.001). There is little likelihood that a genetic or nutritional predisposition accounted for the findings, because the immigrants came from widely scattered parts of the world. Possibly, the immigrants were reluctant to seek medical attention for minor illnesses, thereby giving rise to an apparent but not real increase of thyrotoxicosis in the foreignborn. There was less mental illness diagnosed in the immigrants than in the nativeborn patients, a point against relating the thyroid overactivity to emotional stress. It is suggested that the adjustment of settling in a strange country may be physiologically disturbing in some unknown way and may give rise to an increased incidence of thyrotoxicosis in immigrants.