THYROID-CANCER IN SOUTH-AFRICA - AN INDICATOR OF REGIONAL IODINE DEFICIENCY

Objective. Because follicular thyroid cancers predominate in iodine-de ficient and papillary cancers predominate in iodine-replete population s, we have analysed national and regional (former Transvaal) incidence s of these cancer types as a surrogate measure of the population iodin e nutritional status in South Africa. Design, Statistical analysis, by race and sex, of differentiated thyroid cancers reported to the South African National Cancer Registry (1988), and of the computerised hist ology records of the Department of Anatomical Pathology, SAIMR (Januar y 1990 to June 1994; Transvaal data). Main outcome measures. Relative frequencies of the two cancer types nationally and geographically in t he Transvaal region. Main results. Thyroid cancer was underdiagnosed i n populations other than white, Nationally, follicular histology accou nted for 55% of all differentiated primary thyroid cancers, and predom inated especially in black women; Follicular morphology predominated i n blacks resident in the rural regions of the former Transvaal (58%), while papillary histology predominated in urban areas (of present-day Gauteng), irrespective of race (78%; P = 0.003). Conclusion. The natio nal predominance of follicular thyroid cancer indicates that significa nt iodine deficiency exists in the country as a whole, The observed ur ban-rural differences in prevalences of follicular and papillary cance r types suggest regional differences in the severity of iodine deficie ncy. There is a need for a formal survey of the population iodine nutr itional status in South Africa.