The Journal of Clinical Endocrinology & Metabolism Vol. 82, No. 10 3430-3433
Copyright © 1997 by The Endocrine Society
Prevalence of Goiter and Urinary Iodine Excretion Levels in Children Around Chernobyl1
Kiyoto Ashizawa,
Yoshisada Shibata,
Shunichi Yamashita,
Hiroyuki Namba,
Masaharu Hoshi,
Naokata Yokoyama,
Motomori Izumi and
Shigenobu Nagataki
The First Department of Internal Medicine (K.A., N.Y., M.I., S.N.),
and Department of Preventive Medicine, Atomic Disease Institute (S.Y.,
H.N.), Nagasaki University School of Medicine, Nagasaki 852, Japan;
Department of Epidemiology, Radiation Effects Research Foundation
(Y.S.), Nagasaki 850, Japan; and International Radiation Information
Center, Research Institute for Radiation Biology and Medicine,
Hiroshima University (M.H.), 1–2-3 Kasumi, Minami-ku, Hiroshima 734,
Japan
Address all correspondence and requests for reprints to: Kiyoto Ashizawa, The First Department of Internal Medicine, Nagasaki University School of Medicine, Sakamoto 1–7-1, Nagasaki 852, Japan.
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Abstract
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The prevalence of goiter among children living in areas affected by the
Chernobyl accident was investigated by analysis of data on
approximately 120,000 children examined at five medical diagnostic
centers in Belarus, Russia, and the Ukraine. Examinations of thyroid
gland were conducted with an arch-automatic ultrasonographic instrument
at the five centers under the same protocol. The diagnosis of goiter
was established when the thyroid volume exceeded a limit calculated
from age, height, and body weight of a child. A considerable variation
by region was noted in the prevalence of goiter. Highest in the Kiev
region, the prevalence in the five regions was 54% in Kiev, 38% in
the Zhitomir regions of the Ukraine, 18% in Gomel, 22% in the Mogilev
regions of Belarus, and 41% in the Bryansk region of Russia. Urinary
iodine content was measured in approximately 5700 children, and an
endemic iodine deficient zone was confirmed in the Bryansk, Kiev, and
Zhitomir regions. A significant negative correlation was observed
between the prevalence of goiter and the median level of urinary iodine
content (Spearman’s rank correlation coefficient was -0.35,
P = 0.025).
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Introduction
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THE INCREASE in thyroid diseases and
hematological disorders, especially thyroid cancer and leukemia, has
been a worldwide concern since the Chernobyl accident. Indeed, a
dramatic increase in childhood thyroid cancer has been reported in
Belarus, Russia, and the Ukraine (1, 2, 3, 4, 5, 6, 7), and iodine prophylaxis has
also become an important issue (8).
The affected areas around Chernobyl have been recognized as iodine-
deficient areas, but the prevalence of goiter was not clear (9). It is
therefore necessary to estimate the prevalence of goiter in these areas
as accurately as possible to elucidate the effects of the Chernobyl
accident on the thyroid gland.
Precise measurement of thyroid volume and an objective criterion for
goiter are prerequisites for the accurate estimation of the prevalence
of goiter. We therefore implemented an automatic arch-scanning
ultrasonographic instrument with image recording function for the
thyroid examinations, and established a formula to calculate the
standard thyroid volume for each child from his or her demographic and
anthropometric data.
Part of the Chernobyl Sasakawa Health and Medical Cooperation Project,
the present study was launched 5 yr after the accident to provide
health screening services for children in the affected areas who were
age 0–10 yr at the time of the accident (10, 11). The project has
three major health screening components: 1) measurement of whole body
137Cs; 2) detection of abnormalities in the thyroid gland;
and 3) detection of hematological abnormalities. The examination of
children has been conducted by five cooperative centers: Gomel
Specialized Medical Dispensary in the Gomel region and Mogilev Regional
Medical Diagnostic Center in the Mogilev region, Belarus; Klincy City
Children’s Hospital in the Bryansk region, Russia; Kiev Regional
Hospital No. 2 in the Kiev region, and Korosten Inter-Area Medical
Diagnostic Center in the Zhitomir region, Ukraine. The same equipment,
reagents, and protocol were used in all centers.
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Subjects and Methods
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Subjects
The subjects were 119,178 children (57,529 boys and 61,649
girls) born between April 26, 1976 and April 26, 1986 and examined from
May 15, 1991 to April 30, 1996 at the five cooperative centers in
Gomel, Mogilev, Bryansk, Kiev, and Zhitomir. A breakdown of the
subjects is shown in Table 1
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Table 1. Number of children in five regions examined and who
were diagnosed with goiter from May 1991 to April 1996
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Thyroid examinations
Examination of the thyroid gland was performed with an automatic
arch-scanning ultrasonographic instrument (Aloka-SSD 520, Aloka Co.,
Tokyo, Japan), with a 7.5-MHz annular array transducer 25 mm in
diameter. Children are examined in a supine position with their neck
hyperextended. The transducer transverses 140 mm over the neck in a
waterbath. Images of 11 cross-sections of the thyroid gland are
recorded at 5-mm intervals on an optic disk, then the total volume is
calculated by computerized digitizer (12).
Serum-free thyroxine (FT4) and TSH levels were measured
with an Amerlite hormone analyzer (Amersham, Bunkyo-ku, Tokyo, Japan)
using commercial assay kits, and the immunometric technique based on
enhanced luminescence was used in a non-RIA system. Titers of
antimicrosome antibody and antithyroglobulin antibody were determined
by the reaction of indirect hemagglutination using commercial assay
kits (Fujirebio, Tokyo).
Determination of iodine and creatinine content in the urine was carried
out with an Auto Analyzer II system (Bran+Luebbe, Nordersted, Germany).
This system is sensitive enough to detect 0.1 µg/dL of urinary iodine
in a urine sample of 500 µL (13). The urinary iodine level was
measured in 5710 children selected by the five cooperative centers.
Each child was asked to collect a single sample of urine and to bring
it to the center. The collected samples were frozen at -20 C and kept
until assay at the Mogilev and Kiev centers.
Criterion for goiter
The criterion for goiter is a thyroid volume exceeding the
volume calculated by the following formula:
where age is the age of the child in years at the
time of the examination, height is the height of the child
in centimeters, and body weight is the weight of the child
in kilograms. The formula was derived by a statistical technique of
model selection and linear regression on the basis of demographic and
anthropometric data of 386 boys and 415 girls who were examined at the
Mogilev Regional Medical Diagnostic center and who: 1) were age 5–15
yr at the time of examination; 2) were living in areas that are not
iodine deficient (urinary iodine level being over 10 µg/dL), and
where 137Cs contamination level is <1 Ci/km2;
3) had a whole body 137Cs count <50 Bq/kg; 4) had levels
of TSH and FT4 within normal ranges, i.e.
0.24 
TSH 2.90 mU/L and 10.0 FT4
25.0 pmol/L); 5) had neither antimicrosome antibody nor
antithyroglobulin antibody; and 6) had no thyroid abnormalities as
revealed by ultrasonography, e.g. position, structure,
echogenity, or presence of nodules and cysts (14).
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Results
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Thyroid volume
The median of thyroid volume of children examined at the five
centers is shown in Fig. 1. Figure 1, A
and B show that the thyroid volume of boys and girls was higher in the
Bryansk and Kiev regions than in the other three regions through almost
all age groups. A tendency of increase in thyroid volume with age was
shown among boys and girls, but in girls the increase seemed to cease
at age 14–16 yr (Fig. 1B).
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Figure 1. Median of thyroid volume by age and region
in boys (A) and girls (B) age 0–10 yr at time of Chernobyl accident.
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Prevalence of goiter
Goiter was diagnosed in 42,470 (35.6%) of the 119,178 children. A
breakdown of the children with goiter is shown in Table 1
. The
prevalence of goiter in the Bryansk, Kiev, and Zhitomir regions was
more than two times higher than that in the Gomel and Mogilev regions.
A closer examination of the prevalence of goiter by district in the
five regions (data not shown) indicated the highest prevalence in
almost all districts of the Kiev region, and a relatively high
prevalence in the Bryansk and Zhitomir regions. In contrast, a
relatively low prevalence of goiter was observed in several districts
around Gomel City in the Gomel region, where a high incidence of cancer
has been noted (15).
Urinary iodine concentration
The region-specific distribution of urinary iodine excretion level
measured in the 5710 selected children is depicted by box-and-whisker
plots in Fig. 2. The median level of
urinary iodine contents was as low as 7.0 µg/dL in Bryansk, 8.5
µg/dL in Kiev, 3.9 µg/dL in Zhitomir, 16.9 µg/dL in Gomel, and
17.7 µg/dL in Mogilev, Belarus. We classified these 5710 children
into groups by place of residence and calculated the prevalence of
goiter and the median level of urinary iodine excretion in each group
excluding those with <10 children. As a result, there were 40 groups
consisting of 5652 children, and a significant negative correlation was
observed (Spearman’s rank correlation coefficient = -0.35,
P = 0.025) between the prevalence of goiter and the
median level of urinary iodine excretion (Fig. 3).
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Figure 2. Box-and-whisker plots of urinary iodine
excretion by region. Bottom and top ends of box and bar inside box
correspond to 25th, 75th, and 50th sample percentiles, respectively.
• and  represent extreme values, called outside and far out,
respectively.
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Figure 3. Prevalence of goiter and median of urinary
iodine excretion in children age 0–10 yr at time of accident.
Calculation of prevalence and median was based on measurements of 5652
children living in 40 different places in five regions.
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Discussion
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The traditional diagnosis of goiter is based on palpation and
World Health Organization (WHO) classification (16), but palpation is
subjective and less reliable in children than in adults, and recent
developments in ultrasound technology have facilitated the accurate
measurement of thyroid volume. However, the measurements of thyroid
volume in 30 Japanese adults (data not shown) indicated that the
conventional method for estimation of thyroid volume in each lobe by
the formula of width x length x thickness x 0.52 on
the basis of the ellipsoid model was prone to underestimation of
thyroid volume. The method used in the present study estimated the
thyroid volume accurately, showing a correlation of 0.99 between the
estimated volume and actual volume of surgical thyroid gland specimens
(12).
The formula we used for calculation of standard thyroid volume was
based on a model describing the variation in individual thyroid volume
as a function of several covariates such as age, height, and body
weight. The sex was also considered as a possible covariate, but the
data indicated that the contribution of sex to the variation in thyroid
volume was negligible after adjustment for the other three covariates.
The contribution of iodine level was also negligible after the
adjustment mentioned above. Similar covariates have been used to derive
the standard thyroid volume (17, 18). However, the relationship between
the thyroid volume and covariates was considered separately for each
covariate. Modeling the thyroid volume as a function of multiple
covariates can lead to a reasonable standard thyroid volume even with a
relatively small sample.
Still, the formula for calculation of standard thyroid volume is not
universal, and a different formula should be used for each population.
For example, the thyroid volume of Japanese adults showed a dependency
on sex, age at the time of examination, and body weight, but not on
height (19). However, the statistical line leading to the present
formula is deemed to be universal.
In the present study, the prevalence of goiter showed no association
with whole body 137Cs count nor with 137Cs
contamination level in the place of current residence and the place of
residence at the time of the accident (data not shown). On the other
hand, a significant negative correlation was indicated between the
prevalence of goiter and urinary excretion level.
The lowest prevalence of goiter was observed in the Gomel region, where
the highest incidence of childhood cancer has been reported (15), and
the highest prevalence of goiter was observed in the Kiev region, where
the incidence of childhood cancer is relatively low. These findings may
be related to the fact that the present study was based on examinations
of children commenced 5 yr after the accident. Because a significant
change in iodine nutrition status may have occurred after the accident,
the present study indicates the necessity for studies focusing on the
iodine nutrition status before and after the accident in the area
around Chernobyl.
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Acknowledgments
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We are grateful to the staff members at Gomel Specialized
Medical Dispensary, Mogilev Regional Medical Diagnostic Center, Klincy
City Children’s Hospital, Kiev Regional Hospital No. 2, and Korosten
Inter-Area Medical Diagnostic Center for their hard work in the
examination of children.
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Footnotes
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1 This work was supported by Sasakawa Memorial Health Foundation,
Tokyo, Japan. 
Received January 21, 1997.
Revised May 20, 1997.
Accepted June 19, 1997.
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Abstract
Introduction
