Full text of DOI:10.1007/BF03343994

J. Endocrinol. Invest. 25: 224-228, 2002
Iodine status and goiter prevalence in Turkey before
mandatory iodization1
G. Erdog˘an*, M.F. Erdog˘an*, R. Emral*, M. Bas¸temır*, H. Sav*, D. Haznedarog˘lu**,
¨
M. Ustündag˘**, R. Köse**, N. Kamel*, and Y. Genç***
*Ankara University Medical School, Department of Endocrinology and Metabolic Diseases, **Turkish
Government Ministry of Health MCH and FP General Directorate, ***Ankara University Medical School,
Department of Biostatistics, Ankara, Turkey
ABSTRACT. Endemic goiter is an important pub-
lic health problem in Turkey. Legislation for man-
datory iodization of household salt was passed
in July 1999. Current study is aimed at ascer-
taining the goiter prevalence and iodine nutri-
tion in school-age children (SAC) living in known
endemic areas of Turkey. Sonographic thyroid
volumes (STV) and urinary iodine concentrations
(UIC) of 5,948 SAC from 20 cities were measured
between 1997-1999. STV of 31.8% of the SAC
examined stayed above the upper-normal limits
for the same age and gender recommended by
the World Health Organization (WHO). Goiter
prevalence ranged between 5 to 56% and me-
dian UIC ranged between 14 to 78 μg/l, indicat-
ing severe to moderate iodine deficiency (ID) in
14 and mild ID in 6 of the cities surveyed. Nei-
ther of the cities was found to have sufficient me-
dian UIC levels. The current study shows that en-
demic goiter is an important public health prob-
lem and iodine nutrition is inadequate nation-
wide. It also provides reliable scientific eviden-
ce and shows the need for a controlled and effec-
tive iodine supplementation program nationwi-
de. Mandatory iodization of household salt
seems to be the essential measure taken for the
moment, additional measures may be needed in
the near future.
(J. Endocrinol. Invest. 25: 224-228, 2002)
©2002, Editrice Kurtis
INTRODUCTION
years, but in 1992, ID was under control in only 5 Eu-
ropean countries namely Austria, Switzerland, Fin-
land, Norway and Sweden (6, 7). Consequently, addi-
tional measures were taken following an official do-
cument sent by the World Health Organization
(WHO), the United Nations Children’s Fund (UNICEF)
and by the International Council for Control of Iodine
Deficiency Disorders (ICCIDD), to all European gov-
ernments. However in 1997, ID was still found in an
important number of European countries, or at least
in certain areas of these countries (8). A remarkable
weak point about the ID in Europe has been very
limited information on IDD from the eastern part of
the continent. Although goiter has been known to
be endemic in Turkey for decades, there has been
no systematic national survey, evaluating iodine sta-
tus nationwide until now and limited data evaluating
iodine status were present. Recently, we showed that
severe to moderate iodine deficiency is the major
cause of the goiter endemics observed in the Black-
Sea region and in the capital of Turkey (9). The cur-
rent survey aimed to assess the status of iodine nu-
trition and goiter prevalence in known endemic goi-
ter areas of Turkey nationwide.
Iodine deficiency (ID) and related iodine deficiency
disorders (IDD) are still major, yet unresolved health
concerns for the world. Universal salt iodization is the
agreed strategy for its control (1). Available data in-
dicate that, in 1999 approximately 2.2 billion peo-
ple were at risk of IDD and that 13% of the earth’s
population, were affected by goiter (2). Endemic goi-
ter, a progressive increase with age of goiter preva-
lence, thyroid nodularity, functional autonomy and
occasionally endemic cretinism has been reported
from iodine-deficient communities of Europe during
the last century (2-5). Iodine supplementation, most-
ly by iodization of salt, has been used for decades.
The situation has improved markedly during past
1Poster presentation, no 220, 12th International Thyroid Congress, October
22-27, 2000, Kyoto, Japan.
Key-words: Endemic goiter, iodine deficiency, iodine prophylaxis.
Correspondence: Dr. Murat Faik Erdog˘ an, Ibni- Sina Hastanesi, Endokrinoloji
ve Metabolizma Hst., B.D., 10. Kat, D Blok, 06100 Sıhhiye, Ankara, Turkey.
E-mail: murat.erdogan@temd.org.tr
Accepted September 6, 2001.
224

G. Erdog˘an, M.F. Erdog˘an, R. Emral, et al.
SUBJECTS AND METHODS
Subjects
100ꢀ) apparatus, using a 7.5 MHz linear array
transducer. Longitudinal and transverse scans
were performed, 3 dimensions were obtained
from each thyroid lobe and thyroid volume was
calculated according to the formula of the ellip-
soid model proposed by Brunn et al. (12) and
proved to be effective for assessment of goiter in
children (13). Upper-normal limits (percentile 97)
for the age and gender matched iodine-replete
European children were used to define the goi-
ter (14, 15).
The investigation included 5,948 school-age children
(SAC) (2,984 girls and 2,964 boys) aged 9-11 yr. This
number was the required sample size based on an
anticipated prevalence of goiter according to the
previous palpation data (10, 11) and on the desired
precision of 4 to 9%. Study population from 20
cities represents a population of 9,096,458 nation-
wide (Table 1). Field studies started in 1997, were
completed in May 1999, before the mandatory
iodization of table salt in Turkey. However uncon-
trolled and weak iodine supplementation was start-
ed in some parts of Turkey 5 years ago. Ultrasound
was performed and urine samples were collected
from all of the children.
Urinary-iodine determinations
Urine samples were kept covered up and frozen at
–20 C, in deionized tubes until the day of analysis.
Urinary iodine excretion was determined by a col-
orimetric method recommended by WHO-ICCIDD
(Calorimetric ceric ion arsenous acid wet ash me-
thod based on Sandell Kolthoff Reaction). Fisher®
reagents and spectronic 20, Genesis autoanalyzer
Thyroid volume
Thyroid volumes were estimated using real-time
ultrasonography with a General Electric® (Logic
Table 1 - Goiter prevalence, median urinary iodine concentrations (UIC) and mean SD sonographical thyroid volumes of 5,948 school
age children (SAC) surveyed according to the anticipated goiter prevalence from 20 cities of Turkey.
City
Population
Goiter prevalence
% (no.*)
Thyroid volume
mean S.D. (ml)
UIC median
(μg/l)
Ankara
Kastamonu
Bayburt
Trabzon
Burdur
Isparta
Konya
2.984.099
59.145
25 (no.=303)
40 (no.=303)
42 (no.=306)
39 (no.=314)
27 (no.=394)
25 (no.=394)
15 (no.=187)
22 (no.=394)
33 (no.=383)
17 (no.=386)
17 (no.=243)
45 (no.=151)
34 (no.=151)
8 (no.=230)
7.16 3.85
7.69 3.21
8.48 4.59
8.22 2.86
7.24 3.15
7.37 3.19
6.59 3.35
7.63 2.21
8.17 2.63
6.09 2.43
6.39 2.77
8.31 3.98
7.50 3.78
5.30 2.21
5.02 1.87
4.56 1.93
5.12 2.79
8.32 2.11
9.24 2.70
8.24 2.69
25.5
30.5
16.0
14.0
21.0
28.0
41.0
48.0
19.0
37.0
43.5
78.0
20.0
61.5
53.0
59.5
51.0
78.0
46.5
25.5
38.453
177.904
87.568
158.930
702.842
159.093
325.396
289.081
641.616
465.807
409.268
207.195
129.627
201.913
1.160.395
134.400
195.350
568.376
9.096.458
Erzincan
Erzurum
Van
Diyarbakır
Malatya
Samsun
Çorum
Bolu
5 (no.=187)
Kütahya
Bursa
6 (no.=178)
7 (no.=385)
Edirne
Aydın
42 (no.=384)
56 (no.=394)
33 (no.=288)
31.8 (no.=5.948)
Kayseri
Total
*Required sample size based on an anticipated prevalence of goiter determined according to the previous palpation data (9, 10). Desired precision was
4 to 9% decided according to the predicted goiter prevalence for the individual city.
225

Iodine status and goiter prevalence in Turkey
(16, 17) were used. The results were calculated as
micrograms of iodine per liter urine (μg/l) and are
expressed as a median.
Diyarbakır, Çorum, Bolu, Kütahya and Bursa, Table
1, Fig. 1). Median UIC indicated severe ID in
Bayburt, Trabzon and Erzurum (i.e. <20 μg/l, Table
1, Fig. 1). Eleven of the cities studied revealed mod-
erate ID having median values between 20-49 μg/l
(i.e. Ankara, Kastamonu, Burdur, Isparta, Konya,
Erzincan, Van, Diyarbakır, Samsun, Aydın and
Kayseri, Table 1, Fig. 1). Six cities showed mild ID,
UIC in between 50-100 μg/l (i.e. Malatya, Çorum,
Bolu, Kütahya, Bursa and Edirne, Table 1, Fig. 1).
Median UIC were comparable with the severity of
goiter endemics in 11 of the cities studied. How-
ever, in 6 cities (i.e. Kastamonu, Malatya, Samsun,
Edirne, Aydın and Kayseri, Table 1, Fig. 1) median
UIC values reported were relatively higher, and in 3
cities (i.e. Konya, Van, Diyarbakır, Table 1, Fig. 1)
relatively lower than what would be accepted for
the observed goiter prevalence.
Statistical methods
Commonly used statistical methods (mean, medi-
an and proportions) were applied to analyze the
data. The Kolmogorov-Smirnov test indicated that
the distribution of thyroid volumes and urinary io-
dine were not normal. As regards urinary iodine,
normalization did not occur after a logarithmic
transformation and as advised by WHO-ICCIDD
recommendations the medians were used rather
than mean values (1). The normal value for urinary
iodine concentration (UIC) in school children are
medians varying from 100 to 200 μg/l (1).
RESULTS
Goiter prevalence found in 8 of the studied cities
was lower than the predicted prevalence and a larg-
er sample size may be needed to find the actual
goiter prevalence in these areas (Table 1). None of
the cities showed sufficient UIC (i.e. >100 μg/l) and
the overall goiter prevalence among the 5,948 SAC
surveyed was 31.8% (Table 1, Fig. 1).
Results obtained from 20 cities are presented in
Table 1 and a map summarizing goiter prevalence
and median UIC is given in Figure 1. Actual goiter
prevalence found excedeed 30%, indicating severe
ID in 9 of the cities (i.e. Kastamonu, Bayburt, Trab-
zon, Erzurum, Malatya, Samsun, Edirne, Aydın and
Kayseri, Table 1, Fig. 1) (1). Ankara, the capital,
Burdur, Isparta and Erzincan showed goiter preva-
lence between 20 and 29.9%, indicating moderate
ID. Seven of the cities displayed goiter prevalence
from 5 to 19.9% indicating mild ID (i.e. Konya, Van,
DISCUSSION
This study attempted to evaluate goiter prevalence
and iodine nutrition in 9-11 year-old SAC from 20
Edirne
Black Sea
Black Sea
N
Kastamonu
40%
42%
Samsun
78.0 ꢀg/l
Trabzon
39%
14.0 ꢀg/l
W
E
34%
30.5 ꢀg/l
ꢀ
Bolu
5%
20.0 ꢀg/l
Bayburt
42%
S
C¸ orum
53.0 ꢀg/l
8%
61.5 ꢀg/l
Erzurum
33%
Bursa
7%
51.0 ꢀg/l
16.0 ꢀg/l
Ankara
25%
19.0 ꢀg/l
Erzincan
22%
48.0 ꢀg/l
25.5 ꢀg/l
Kütaya
6%
59.5 ꢀg/l
Kayseri
Van
Malatya
33%
17%
45%
Diyarbakır
Isparta
25.5 ꢀg/l
Konya
15%
45.0 ꢀg/l
37.0 ꢀg/l
78.0 ꢀg/l
17%
Aydın
25%
43.5 ꢀg/l
56%
28 ꢀg/l
46.5 ꢀg/l
Burdur
27%
Iraq
21.0 ꢀg/l
1:10.000.000
125 km
Syria
0
Mediterranean Sea
Fig. 1 - Prevalence (%) and median urinary iodine concentrations of the school age children (SAC) sur-
veyed from 20 cities of Turkey.
226

G. Erdog˘an, M.F. Erdog˘an, R. Emral, et al.
known endemic cities of Turkey. 5,948 SAC sur-
veyed represents a population of 9,096,458 living
nationwide. Two standard methods, namely sono-
graphic thyroid volumes (STV) measured by ultra-
sonography and UIC were used.
centration in salt and urine of individuals, are cur-
rently being undertaken. Additional measures may
be needed in the near future.
ACKNOWLEDGEMENTS
Severe to moderate ID was remarkable in 14 of
the cities studied. Median UIC was comparable
with the severity of goiter endemics, observed in
11 of the cities surveyed. Relatively higher medi-
an UIC, even higher than the elevate goiter preva-
lence observed in 6 cities, seems to be a conse-
quence of an inadequate iodine supplementation
program which was started 5 years ago with the
iodization of table salt. In three of the cities where
goiter prevalence stayed relatively low when com-
pared to the moderate ID determined (i.e. Konya,
Van, Diyarbakır, Table 1, Fig. 1), goiter prevalence
found was also lower than the predicted values
and increasing the sample size would be appro-
priate for these cities. In four of the cities (i.e. C¸o-
rum, Bolu, Kütahya and Bursa, Table 1, Fig. 1) al-
though the goiter prevalence reported was rele-
vant with the mild ID observed, the predicted
prevalence stayed well over the prevalence
found. This may reflect the improving situation in
these areas in the last decade or it might be due
to the misleading palpation data from older stud-
ies conducted in these areas (11). An increment
of the sample size may also be needed in these
areas.
None of the cities studied, showed sufficient me-
dian UIC (i.e. >100 μg/l). Similarly, sonographic
goiter prevalence reported was systematically
higher than 5% in the study areas, which indicates
that goiter is endemic nationwide. This survey also
showed that severe to moderate ID is the major
cause of the goiter endemics observed in Turkey.
Other more dramatic consequences of ID, like en-
demic cretinism are beyond the scope of this study
and are not being thoroughly investigated in
Turkey. Median UIC indicating the severe ID
reached in some cities is relevant in those parts of
the world where endemic cretinism had been re-
ported (18).
This study has been supported by the Turkish Government, by
the Mother Child Health and Family Planning General Direc-
torate of the Ministry of Health, United Nations Children’s Fund
-UNICEF Turkey, University of Ankara Research Fund, ICCIDD-
International Council for Control of Iodine Deficiency
Disorders-Brussels, Belgium and TÜBITAK-The Scientific and
Technical Research Council of Turkey. We would like to thank,
Dr. François Delange for the scientific support; Dr. Bilkay
Kolog˘ lu and S¸ehnaz Akalın for the laboratory work; Our nurs-
es Suzan Durmaz, Nuran Okur and Ays¸e Ates¸ for the field stud-
ies; Our secretaries Nurhan Bozkurt and Davut Böcek for their
generous efforts in this survey.
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