Comparison of Urine and Milk Iodine Concentration among Congenitally Hypothyroid Neonates and Their Mothers and a Control Group

Although Iran is known as an iodine sufficient area, congenital hypothyroidism (CH) is prevalent. Because iodine excess can contribute to hypothyroidism, we evaluated the role of iodine excess and ID in the etiology of CH. Methods and Materials: In a cross sectional study UICs (Urine Iodine Concentration) in newborns with CH as well as UIC and MIC (Milk Iodine Concentration) of their mothers were compared with a control group. After acid digestion of urine samples milk samples, iodine concentrations were determined by the Sandell-Kolthoff method. Chi-square and Wilcoxon, and Pearson correlation tests were used for statistical analysis. A P value less than 0.05 was considered statistically significant. The median of MIC of CH (n=68) and healthy subjects (n=179) was different (210 vs. 170 µg/L respectively, P<0.05). However the median of UIC in neonates and those of mother's of CH and healthy subjects were not different statistically (305 vs. 300µg/L and 150 vs.130µg/L respectively, P>0.05) 71.2% and 46.7% of mothers of hypothyroid and healthy subjects had MICs above 180 µg/l (iodine excess) respectively (p=0.002). Based on the higher levels of MIC in mothers of CH neonates, iodine excess could be a possible risk factor for CH. Since however comparison of UIC between the control and neonate groups showed no differences, further investigations are needed to facilitate deeper insight into and clarification of the etiology of CH.