Normal values of thyroid ultrasound volume of School children in non-iodine defi-ciency area Abomey Calavi in Benin

Abstract

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 300μg / 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.