International Research Journal of Biological Sciences ___________________________________ ISSN 2278-3202Vol. 2(9), 29-33, September (2013) Int. Res. J. Biological Sci. International Science Congress Association 29 Normal values of Thyroid Ultrasound Volume of School Children in non-iodine deficiency area Abomey Calavi in BeninGbaguidi Bertin,Ahokpe Mélanie, Attakpa Eugène, Ategbo J. Marc, ASSOU Eudoxie, Aïvodji Natacha, Amoussou-Guenou Marcelin and Sezan Alphonse* Laboratoire de Biomembranes et de Signalisation Cellulaire, Département de Physiologie Animale, Faculté e des Sciences et Techniques, Université d’Abomey- Calavi, Cotonou, REPUBLIQUE DU BENINAvailable online at: www.isca.in Received 16th May 2013, revised 5th June 2013, accepted 30th July 2013Abstract According to WHO, the school-age children are more vulnerable to disorders caused by iodine deficiency (IDD). The prevalence of goiter in this age is an indicator of the severity of these disorders in a population. Assessing the prevalence in a moderately iodine-deficient area is more reliable by measurement of thyroid ultrasound volume (TUV) than palpation method. This study aims to define the upper limits of normal TUV which can be referenced in school children aged 06 to 12 years of Abomey-Calavi. A coastal city apparently without iodine deficiency and the most populous of Atlantic Department in southern Benin. Inclusion criteria were formulated. Children were selected at random in a cluster of 09 schools. For each of them, urinary iodine was measured, anthropometric parameters (age, sex, height, weight) were recorded and ultrasound explorations were performed to calculate TUV. The normal upper limits are the 97th percentiles of TUV calculated firstly according to age and sex and the other based on sex and body surface area (BSA). Study population includes 134 schoolchildren, 68 girls (50.70%) and 66 males (49.3%). The urinary iodine was between 100 µg / l and 300g / l in 93.3% of children and 300 and 400 µg / l for others. In girls, 97th percentiles of TUV were respectively by age categories (06 to 12) years: 1.99 ml; 2.71 ml; 2.06 ml; 2.54 ml; 4.70 ml; 3.81 ml; 5.22 ml. For boys, respectively: 1.82 ml ; 2.11 ml ; 2.19 ml ; 2.80 ml ; 3.06 ml ; 4.6 ml ; 3.9 ml. TUV were normal in 91.04% of children. According to BSA, 97th percentiles of TUV for girls were: 2.04 ml; 3.86 ml; 2.05 ml; 3.63 ml, 4.7 ml, 5.25 ml, 3.88 ml, 4.38 ml, in boys nc; nc; 1.19 ml; 2.89 ml; 3.52 ml; 3.93 ml; 4.22 ml; 4.83 ml; nc (nc = not considered). The TUV were normal in 88.06% of schoolchildren. Upper limits of normal TUV values obtained wee fairly consistent and could serve as references for the interpretation of survey and monitoring data obtained by ultrasound in school children. Keywords: Normal values, thyroid ultrasound volume, iodine deficiency, schoolchildren, abomey-CalaviIntroduction According to WHO, the schoolchildren are more vulnerable to iodine deficiency disorders (IDD). Thus, the prevalence of goiter in this age is a fairly reliable indicator of the severity of these disorders in a population. Assessing the prevalence in a moderately iodine-deficient area is more reliable by measurement of thyroid ultrasound volume (TUV) than palpation method2-5. In such areas, palpation method has a very low sensitivity and specificity. Palpation increases the risk of overestimating goiter prevalence and interobserver variability is high. However, the application of the ultrasound method requires some precautions. Indeed, in the context of epidemiological investigation, detecting and monitoring IDD requires referential TUV data unfortunately vary from one country to another5,8,9. Each country must therefore, establish its own referential standards of TUV to better assess IDD in the population. Our study aim to determine the upper limits of normal TUV basis on sex, age and body surface area among schoolchildren in Abomey-Calavi,a coastal city apparently without iodine deficiency and the most populous of Atlantic Department in southern Benin. Material and MethodsOur study population includes children of both sexes aged 06 to 12 years selected at random in a cluster of 09 primary schools in Abomey-Calavi. For each of them, urinary iodine was measured, anthropometric parameters (age, sex, height, weight) were recorded and ultrasound explorations were performed to calculate TUV. Determination of urinary iodine: Urine samples were taken in the morning at 08 o'clock. The iodine concentration was measured at the Research Unit Ecotoxicology and Quality Study (UREQ) at Polytechnic School of Abomey-calavi through Sandell-Kolthoff method10. This assay was used to verify the iodine status of our population in order to certify its non-iodine deficiency. Anthropometric data: Age and Sex: Age was determined by year from the birth certificate or school record. Sex was recorded on the survey sheet for each child. International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(9), 29-33, September (2013) Int. Res. J. Biological Sci. International Science Congress Association 30 Weight: schoolchildren were weighed using a mechanical scale brand CAMRY iso 9001:2008 witch limit of detection ranging between 0 and 120kg. Before any measurement, each child had discarded his shoes and any compromising object and dressed in a negligible weight jacket. Size: The size (in cm) was taken in a static position in the same terms as weight, using a tape stuck against a vertical board. Body surface area (BSA) in m: DUBOIS formula was used to estimation BSA. BSA= W0, 425 x S 0,725 x 71, 84 x 10-4 11W=Weight; S=Size. Ultrasound data: The thyroid ultrasound was performed in real time in schools. A portable ultrasound SIEMENS with a 7.5 MHz linear probe was used. All measurements were performed by one and only one investigator, specialist in thyroid ultrasound. To measure thyroid volume, longitudinal and transversal sections had been made to determine the thickness (t) in centimeters, the breadth (b) and length (L) of each thyroid lobe. Thyroid lobe volume (VL) in cm was calculated from the formula: VL = t x b x L x (0.479)12. Isthmus volume had been neglected. TUV was therefore the total obtained by adding the volume of two lobes. TUV were calculated firstly according to age and sex, on the other based on sex and BSA. The normal upper limits used are 97th percentiles of TUV as recommended by WHO and ICCIDD13 adapted by Zimmermann14. Statistical Analysis: Epi Info 3.5.3 French and Microsoft Excel 200715,16 were used for Data Processing. Statistics related to the mean, median, standard deviation, the minimale, maximum and 97th percentile were used to analyze the dimensions. Results and Discussion 134 schoolchildren aged 06 to 12 years, 68 girls (50.70%) and 66 males (49.3%) were included in this study. The sex ratio was 1.03. The youngest was a girl while the oldest was a boy. Table 1 shows the frequency distribution of urinary iodine concentrations. Almost all schoolchildren (93.30%) had a urinary iodine levels between 100 and 300g/l, while the other (6.70%) have a rate between 300 and 400 g/l, indicating an excess of iodine. Table-1 Distribution of schoolchildren according to the urinary iodine levels Urinary iodine (µg/l) Number Frequency 100-200 62 46,30 200-300 63 47,00 300-400 9 6,70 Total 134 100 Tables 2 and 3 present respectively, comparisons of normal upper limits of TUV in terms of age, sex with international standards. Abomey is not a known endemic goiter area. The median urinary iodine 210g/l confirms that the area is not iodine deficiency. However, the prevalence of goiter detected, is respectively 8.96% and 11.94%, by age and sex, sex and body surface area. In the group of girls, the 97th percentile of TUV by age varies from 1.99 to 5.22 ml (table 2); in males from 1.82 to 4.01ml (table 3). Based on body surface, TUV varies in girls group from 2.04 to 4.38 ml (table 4); in boys due to low staffing problem, we considered BSA between 0.8 and 1.3 m. Therefore in this part of BSA, the 97th percentile of TUV varies from 1.19 to 4.83 ml (table 5). Table-2 Comparison of upper limits of normal (T function age) girls with international standards Age P50 Zimmermann22 50 ThyroMobil west Africa23 50 Current study 97 Zimmermann22 97 ThyroMobil west Africa23 97 Current study 6ans 1,57 1,9 1,44 3284 3,4 1,99 7 ans 1,81 2,2 2,09 3,26 3,5 2,71 8 ans 2,08 2,2 1,82 3,76 3,6 2,06 9 ans 2,40 2,3 1,56 4,32 3,6 2,54 10 ans 2,76 2,4 2,94 4,98 3,7 4,70 11 ans 3,17 3,2 3,24 5,73 4,5 3,81 12 ans 3,65 3,3 3,49 6,59 7,6 5,22 International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(9), 29-33, September (2013) Int. Res. J. Biological Sci. International Science Congress Association 31 Table-3 Comparison of normal upper limits of VET (age based) boys with international standards Age 50 Zimmermann(WHO)2250 ThyroMobil West Africa23 50 Current study 97 Zimmermann(WHO)2297 ThyroMobil West Africa23 97 Current study 6ans 1,60 2,0 1,21 2,91 3,1 1,82 7 ans 1,80 2,1 2,03 3,29 3,1 2,11 8 ans 2,03 2,4 1,08 3,71 3,4 2,19 9 ans 2,30 2,5 1,81 4,19 3,5 2,80 10 ans 2,29 2,6 2,57 4,73 4,3 3,09 11 ans 2,92 3,1 2,78 5,34 4,7 4,88 12 ans 3,30 3,8 2,67 6,03 6,6 4,01 Table-4 Comparison of upper limits of normal (TUV function BSA) girls with international standardsBSA P 50 Zimmermann (WHO) 22 P 50 . Current study P 97 Zimmermann (WHO) 22 P 97 Current study 0,7m 2 1,46 1,81 2,56 2,04 0,8m 2 1,67 2,16 2,91 3,86 0,9m 2 1,9 1,76 3,32 2,05 1,0m 2 2,77 2,06 3,79 3,63 1,1m 2 2,47 3,19 4,32 4,70 1,2m 2 2,82 3,16 4,92 5,25 1,3m 2 3,21 3,03 5,61 3,88 1,4m 2 3,66 4,08 6,40 4,38 Table-5 Comparison of upper limits of normal (TUV function BSA) boys with international standards BSA P 50 Zimmermann (WHO) 22 P 50 Current Study P 97 Zimmermann (WHO) 22 P 97 Current Study 0,7m 2 1,47 - 2,62 - 0,8m 2 1,66 1,42 2,95 1,19 0,9m 2 1,86 2,05 3,32 2,89 1,0m 2 2,10 2,61 3,73 3,52 1,1m 2 2,36 2,55 4,2 3,93 1,2m 2 2,65 3,14 4,73 4,22 1,3m 2 2,99 4,01 5,32 4,83 1,4m 2 3,36 - 5,98 - Figure-1 Comparison of TUV schoolchildren calculated according to age with the 2004 WHO reference (a: Male b: Girls) 1.571.812.082.42.763.173.652.843.263.764.324.985.736.596789101112 \n \rAge p50 AB p97 AB p50 OMS 1.61.82.032.32.592.923.32.913.293.714.194.735.346.036789101112 \n \rAge p50 AB p97 AB p50 OMS p97 OMS International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(9), 29-33, September (2013) Int. Res. J. Biological Sci. International Science Congress Association 32 Figure-2 Comparison of TUV schoolchildren calculated based on body surface with the WHO 2004 reference (a: Male b: Girls) Discussion: This study has verified the iodine status and determined normal values of TUV in schoolchildren. The different data are used to assess locally, the effectiveness of battle against IDD through universal salt iodization strategy and extension of the consumption of iodized salt initiated by the government and its partners at household level17. The urinary iodine reflects the consumption standby of iodide level. Thus, the severity of IDD is evaluated based on the median of urinary iodine18. The median urinary iodine level in our sample is 210g/l and any child has a lower rate to 100 g/l. This shows that the schoolchildren of this community do not suffer from a dietary iodine deficiency. However, a total of nine (09) schoolchildren (6.7%) had a urinary iodine levels above 300 mg/l, which reflects an excess of iodine consumption whose consequence is the effect of Wolff –Chaikoff19. The prevalence of goiter sonographically determined by the two sets of thresholds (age, sex) and (SC, sex) are 8.96% and 11.94% respectively. These different rates of persistence quite surprising goiters direct us to several tracks. First, we suspect that due to the mobility of schoolchildren, some of them may immigrate an endemic area to recover sharply in Abomey-Calavi. Now a day, Abomey-Calavi is as we know the new dorm cited which receives every year many transferred children to other schools for various reasons. Under these conditions, the daily iodine intake in the new locality (Abomey-Calavi) will quickly improve urinary iodine levels but have a fairly significant effect on the thyroid volume. This confirms published results in 2001 by WHO and UNICEF indicated that normalization of TUV may be several years after the correction of dietary iodine deficiency. Then, we must also fear the adverse effects of goitrogenic foods on the incorporation of iodine in thyroid gland. An investigation is needed to assess the toxicity of the foods consumed by our schoolchildren. There are foods that contain substances that prevent use of iodine in the body. These substances are divided into three groups: the flavonoids in soybeans decreased intestinal absorption of thyroxin; thioglucosides contained in cruciferous (cabbage, turnip) and cyanoglucosides whose main source is cassava. The cyanoglucosides contain cyanide which is converted in gastrointestinal tract into thiocyanate, a potent inhibitor of the uptake of iodine in the thyroid gland. The link of TUV in relation to sex parameter shows that girls the thyroid volume is comparable to girls than boys (p = 0.095). These results confirm those found by other authors who have worked in areas where iodine intake is adequate8,20,21. Our 50thand 97th percentiles of TUV were compared with WHO references adapted by Zimmermann22 and Thyromobil coastal cities, Cotonou (Benin) and Lomé (Togo)23. Depending on age, our data are slightly lower than international standards both sexes. We must recognize that international standards were published in 2004, in the final phase of the battle against IDD in different countries explored. We can therefore assume that, almost ten years after the fight, TUV had time to undergo regression was significant. The reconciliation of TUV in relation to gender parameter shows that the thyroid volume is comparable to girls than boys (p=0.095). These results confirm those found by other authors who have worked in areas where iodine intake is adequate8,20,21. Our 50th and 97th percentiles of TUV were compared with the 2004 WHO references adapted by Zimmermann22 and Thyromobil coastal cities Cotonou (Benin) and Lomé (Togo)23. Depending on age, our data are slightly lower than international standards data for both sexes. We must recognize that international standards data were published in 2004, during the final phase of the fight against IDD in different countries explored. We can therefore assume that, almost ten years after this fight, thyroid volume had time to undergo a significant regression. 1.471.661.862.12.362.652.993.362.622.953.323.734.24.735.325.980.70.80.911.11.21.31.4 \n \r p50AB p50OMS p97AB p97OMS 1.461.671.92.172.472.823.213.662.562.913.323.794.324.925.616.40.70.80.911.11.21.31.4 \n \rBSA p50AB p50 OMS p97AB p97OMS International Research Journal of Biological Sciences ________________________________________________ ISSN 2278-3202 Vol. 2(9), 29-33, September (2013) Int. Res. J. Biological Sci. International Science Congress Association 33 Conclusion The fight against disorders caused by iodine deficiency requires a permanent and increased surveillance. Under these conditions, the data from our study will be quite obvious utility. Indeed, the normal upper limits of the VET obtained values are fairly consistent and can serve as references for the interpretation of survey and monitoring data obtained by ultrasound in schoolchildren. This study should therefore be generalized to all of our schoolchildren in order to lead to the establishment of national standards of TUV depending on the recommendations of who and UNICEF. References 1.WHO; UNICEF; ICCIDD,Assessment of iodine deficiency disorders and monitoring their elimination. A guide for programme managers. GenevaWHO/NHD01, 1, 107 (2001)2.WHO; UNICEF; ICCIDD, Indicators for assessing iodine deficiency disorders and their control through salt iodization. Geneva: WHO, (WHO/NUT/94.6.) 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