ALMA TOROMANOVIĆ ET AL.: THYROID VOLUME MEASUREMENT BY ULTRASOUND IN SCHOOLCHILDREN FROM MILDLY IODINE-DEFICIENT AREA

Th yroid size was estimated by ultrasound and physical examination in  schoolchildren ( boys and  girls), - years old, living in Tuzla Canton. By physical examination goiter was found in . (n=) of subjects. When compared with the upper limits of the reference thyroid volumes reported by WHO and ICCIDD, goiter by ultrasonography was found in . (n=) of all subjects. All goitrous children had a diff use goiter. Th e diff erences in mean thyroid volumes between groups with and without goiter detected by physical examination were significant in all age groups (p<.). Th e results of ultrasound examinations correlate well with palpatory fi ndings and show higher values for the thyroid volume in children with goiter. It generally confi rms the values of the fi ndings by palpation, even in areas with mild iodine defi ciency.


Introduction
Determination of goiter prevalence and urinary iodine excretion in schoolchildren is recommended for assessing the extent and severity of iodine deficiency disorders in a region ().For years, palpation was the single method available for defining thyroid volume.Although in moderately or severely iodine-deficient areas, thyroid palpation provides careful estimation of thyroid size, serious problems are encountered in areas with mild iodine defi ciency, where most goiters are small.Th yroid ultrasound came to be considered the most reliable method for the estimation of thyroid volume (,).In epidemiological surveys, the use of this technique is strongly recommended to define the goiter endemia in areas of mild iodine defi ciency.In the past, severe iodine defi ciency, endemic goiter and cretinism were documented in restricted areas of Bosnia and Herzegovina.Salt production is present in Tuzla area since the medieval times and salt iodination was initiate in salt plant in Tuzla in .Epidemiological surveys on goiter in Bosnia and Herzegovina were started systematically in the early s.An investigation in  has documented high goiter prevalence in endemic areas, varying from  to .A law proscribing obligatory iodination of all salt for human and animal consumption, with  mg KI/kg of salt was proclaimed in .On the basis of clinical observation of rather high prevalence of goiter among schoolchildren, the study, with the aim to evaluate the effi cacy of compulsory iodine prophylaxis more than  years after its introduction, was carried out in all cantons in Bosnia and Herzegovina Federation in  ().Th e results of the study show the persistence of mild iodine defi ciency in Tuzla Canton on the basis of median urinary iodine excretion of . μg/L and goiter prevalence of . in schoolchildren.Thyroid size was estimated by physical examination.Th e aim of the present study was to measure thyroid volume and evaluate the prevalence of endemic goiter by ultrasound criteria in the schoolchildren population in mildly iodine-defi cient area of Tuzla Canton.

Subjects and Methods
Th yroid size was assessed by ultrasound and by physical examination in  schoolchildren ( boys and  girls) - years old, randomly selected, in Tuzla Canton.Tuzla Canton is one of the ten administrative territorial units of the Federation of Bosnia and Herzegovina, situated in North-Eastern Bosnia.Th yroid size was estimated by neck palpation, by the same examiner, and graded according to the World Health Organization (WHO)/International Council for the Control of Iodine Deficiency Disorders (ICCIDD) criteria () as follows: grade  -no palpable or visible goiter; grade a mass in the neck that is consistent with an enlarged thyroid that is palpable but not visible when the neck is in the normal position, it moves upward in the neck as the subject swallows; grade : a swelling in the neck that is visible when the neck is in a normal position and is consistent with an enlarged thyroid when the neck is palpated.Th yroid ultrasound was performed by the same examiner.Subjects were examined in supine position with the neck hyperextended.Th yroid volume was estimated using real-time sonography according to Brunn et al. () with Toshiba SSA-A, using a . MHz linear transducer.Longitudinal and transverse scans were performed allowing the measurement of the depth (d), the width (w) and the length (l) of each lobe.Th e volume of the lobe was calculated using formula: V(ml)=.x d x w x l (cm).Th e thyroid volume was the sum of the volumes of both lobes.Th e volume of the isthmus was not included.The criteria used for defi ning the upper limit of normal for thyroid volume (percentile ) in children with a normal iodine intake were those proposed by WHO/ICCIDD ().

Results
Th e mean thyroid volume as determined by ultrasonography was .±.ml.Although the mean thyroid volume was greater in girls (.±.)than in boys (.±.) the diff erence was not statistically signifi cant (p>.).Th e results of the ultrasound examinations confi rmed the fact that the right lobe (.±.) of the thyroid gland is larger, compared to the left lobe (.±.), and the diff erence is signifi cant (p<.).Mean and median thyroid volumes of all subjects according to age are shown in Table .The median thyroid volume increases from . ml at  years to . ml at  years.Signifi cant positive correlation was observed between the thyroid volume and age (r=.,p<.).Also, signifi cant correlation was found between thyroid volume and body weight of children (r=.,p<.), height (r=.,p=.) and body surface (r=.,p<.).When compared with the upper limits of the reference thyroid volumes, goiter by ultrasonography was found in . (n=) of all subjects (n=).All goitrous children had a diff use goiter.By physical examination goiter was found in . (n=) of subjects.Mean and median thyroid volumes according to age in subjects with and without goiter by physical examination are shown in Table .Th e diff erences of mean thyroid volumes between groups with and without goiter detected by physical examination were signifi cant in all age groups (p<.).

Discussion
Thyroid ultrasound is reliable, practical and objective method of determining thyroid size.The results of the ultrasound examinations confirmed the fact that the right lobe of the thyroid gland is larger, compared to the left lobe ().Thyroid volume is well correlated with age and growth parameters, what was reported also in this survey (,).When the upper limits of reference thyroid volumes were taken into account (), we found goiter prevalence of . in the studied population.Th is fi nding was in accordance with the prevalence of goiter (.) ob-tained by physical examination.Th e volumes of thyroid gland in children where goiter was found by palpation and the volumes in children without goiter are compared and presented separately.Th e results of the ultrasound examinations correlate well with the palpatory fi ndings and show higher values for the thyroid volume in children with goiter, which generally confi rms the values of the fi ndings by palpation.Th e recent studies (,) indicate that thyroid ultrasonography is more accurate than palpation in the assessment of goiter prevalence in the schoolchildren population living in mildly iodinedefi cient areas.Th ey have shown that palpation overestimates the actual size of thyroid, particularly in children.On the contrary, the data reported in this study indicate that physical examination is as precise as ultrasonography in the assessment of goiter prevalence in mildly iodine-defi cient areas.Th is may be explained by the fact that this study was performed by the same investigator.Our findings for the volume of thyroid gland were  BOSNIAN JOURNAL OF BASIC MEDICAL SCIENCES 2005; 5 (1): 19-22 compared to the values of other authors.Our values are higher than the values of Gutekunst et Martin-Teichert () for Sweden, where there is no deficiency, are lower than the values of Semiz et al. () for goitrous area of mild to moderate degree from Turkey and are similar to the values of Aghini-Lombardi et al. () that refer to goitrous region in Italy

Conclusion
In conclusion, the ultrasound data indicate mild degree of iodine deficiency in Tuzla Canton.Although ultrasonography provides more precise measurement of thyroid volume compared with palpation, clinical examination in the assessment of goiter prevalence in mildly iodine-defi cient areas should not be abandoned.