Effect of 10 yr of the iodine supplementation on the hearing threshold of iodine deficient schoolchildren

Abstract

Objective: Auditory disturbances may be present in iodine deficient children. The aim of this study was to determine the effect of long-term iodine supplementation on auditory thresholds in iodine deficient children. Design and methods: 70, 70 and 72 schoolchildren of an area of severe iodine deficiency were studied before intervention (1989), 3 yr after injection of 480 mg iodized oil (1992) and 7 yr after consumption of iodized salt (1999), respectively. Goiter was graded and serum T 4 , T 3 , TSH and thyroglobulin concentrations and urinary iodine levels were measured. Audiometry was performed with a pure tone audiometer. Results: There was significant decrease in the prevalence and severity of goiter and serum TSH and thyroglobulin concentrations, and significant rise in serum T 4 in 1992 and 1999, as compared to 1989. Before iodine supplementation, hearing was abnormal in 44% of schoolchildren, mean hearing threshold was 15.8±5.9 and in all children was > 10 dB. Mean hearing threshold decreased to 10.2±4.6 and 10.0±5.9, 3 and 10 yr after intervention (p < 0.001). Forty seven and 62% of children had thresholds < 10 dB in 1992 and 1999, respectively. Hearing thresholds > 15 dB were detected in 46, 11 and 10% of schoolchildren in 1989, 1992 and 1999, respectively (p < 0.001). Conclusion: Continuous iodine supplementation permanently improves the auditory thresholds of iodine deficient children. ©2005, Editrice Kurtis.