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Table 3 Prevalence of occult thyroid cancer in adults at autopsy, by national iodine status. National population iodine status at the time of study as categorized according to WHO criteria for the median urinary iodine concentration (UIC) [23].a

From: Iodine intake as a risk factor for thyroid cancer: a comprehensive review of animal and human studies

Country (reference) Year No. autopsy cases % with occult thyroid cancer
Probable deficient iodine intake (UIC < 100 μg/L) (n = 11)
Italy [151] 1982 111 3.6
Chile [152] 1984 274 2.9
Poland [108] 1975 110 6.6
Portugal [153] 1979 600 1.0
Israel [154] 1981 260 4.2
Germany [155] 1987 1020 6.1
Spain [156] 1993 100 22.0
Belarus [157] 1993 215 8.8
Ukraine [158] 1996 162 10.8
Guatemala [159] 2005 150 2.0
Hungary [109] 2005 222 5.0
Mean    6.6
Weighted mean    5.3
Probable sufficient iodine intake (UIC = 100–299 μg/L) (n = 10)
Canada [108] 1975 100 6.0
Sweden [160] 1981 500 6.4
USA [161] 1988 138 2.9
Brazil [162] 1989 300 1.0
Argentina [163] 1989 100 11.0
Iceland [164] 1992 199 6.0
Singapore [165] 1994 444 9.0
Austria [110] 2001 118 8.6
Greece [166] 2002 160 5.6
Turkey [167] 2011 108 3.7
Mean    6.0
Weighted mean    6.0
Probable excessive iodine intake (UIC ≥ 300 μg/L) (n = 10)
USA [168] 1952 429 0.9
USA [169] 1955 1000 2.8
USA [170] 1955 221 1.4
USA [171] 1964 100 4.0
USA [172] 1966 300 2.7
USA [173] 1969 220 0.5
USA [174] 1974 157 5.7
Columbia [108] 1975 607 5.6
Hungary [109] 2005 221 4.5
Brazil [175] 2006 166 7.8
Mean    3.6
Weighted mean    3.3
Studies of Japanese populations in areas of excessive iodine intake (n = 5)
USA, Japanese [176] 1971 100 24.0
Japan [174] 1974 1096 17.9
USA, Japanese [108] 1975 248 24.2
Japan [108] 1975 1167 28.4
Japan [111] 1990 408 15.7
Mean    22.0
Weighted mean    22.4
  1. aWeighted means of iodine intake categories compared by using the Chi-squared test of independence: <100 μg/L vs. 100–299 μg/L (p = 0.244); ≥300 μg/L vs. <100 μg/L or 100–299 μg/L (both, p < 0.001)