Comparative ultrasound measurement of normal thyroid gland dimensions in school aged children in our local environment.

OBJECTIVE The objective of this study was to determine the measurement of normal range of ultrasound (US) thyroid gland dimensions in school-aged children (6-16 years) in our environment and compared with what is obtained elsewhere. SETTING AND DESIGN A prospective ultrasound measurement study done in University of Benin Teaching Hospital Benin, Nigeria. MATERIALS AND METHODS A prospective ultrasound (US) study of thyroid dimensions of 500 school-aged children in our environment consisting of 227 boys and 273 girls was done from 1 December 2006 to July 2007. The subjects were examined by the authors and subjects with palpable abnormal thyroid gland were excluded from the study. The thyroid dimensions (length, height, and diameter) were taken for each lobe by means of ultrasound (US). In addition volume of each thyroid lobe was calculated and the summation of volume of the lobes was taken as thyroid gland volume of each subject. Also height and weight of patients were documented from which the subject's body surface was calculated. Incidental thyroid gland lesion in US was excluded from the study. Using the Statistical program of social science (SPSS) and INSTAT (Graph Pad Inc. USA) the data were analyzed. Informed consent was obtained from all the subjects and the study was done in line with the ethical guidelines of the centers. RESULTS The US thyroid gland volume in school-aged children in Benin City from this study ranges between 1.17 cm 3 and 7.19 cm 3 , mean volume range of 1.76-4.95 cm 3 , median volume range of 1.73-4.73 cm 3 , and range of standard deviation from 0.39 cm 3 to 1.49 cm 3 . The average mean thyroid volume is 2.32 cm 3 with the following average dimensions; anteroposterior right lobe =1.06 cm, mediolateral right lobe = 1.01 cm and craniocaudal right lobe = 2.34 cm, and anteroposterior left lobe = 1.01 cm, mediolateral left lobe = 1.04 cm and craniocaudal left lobe = 2.41 cm for both boys and girls respectively. These data are significantly lower than data obtained by European based World Health Organization/International Council for the Control of Iodine Deficiency Disorders (WHO/ICCIDD) 1997. However there is significant similarity with data obtained in similar environment. CONCLUSION Ultrasound thyroid gland dimensions in school-aged children in our environment are reproducible and the data obtained are comparable to those obtained in other environment. The values may be better used in our environment as reference data for screening purposes.