Urine and milk iodine concentrations in healthy and congenitally hypothyroid neonates and their mothers

Abstract

Introduction: In view of the high prevalence of Congenital Hypothyroidism (CH) in Iran, in this study we evaluated the role of iodine in the aetiology of CH by comparing urine and milk iodine concentrations in healthy and congenitally hypothyroid neonates and their mothers.
Material and methods: In a cross-sectional study, urinary iodine concentrations (UIC) in newborns with CH, as well as UIC and the milk iodine concentrations (MIC) of their mothers, were measured and compared with a control group. The lower, mid, and upper range of UIC for neonates and lactating mothers was considered to be < 150 mg/L, 150-230 mg/L, and > 230 mg/L, and lower, mid, and upper range of MIC was considered to be < 150 mg/L, 150-180 mg/L, and > 180 mg/L, respectively.
Results: The median UICs in subjects with CH (n = 68) and healthy subjects (n = 179) were 300.5 and 290.5 mg/L, respectively (P > 0.05). The median UICs in the case and control groups were 150 and 130 mg/L, respectively (P > 0.05). The median MIC in the case group was higher than in the control group (210 mg/L v. 170 mg/L, P < 0.05).There was a positive correlation between newborn UIC and MIC. There was no significant correlation between newborn UIC and serum TSH, maternal UIC and maternal MIC, or newborn UIC and serum TSH.
Conclusions: There is no inadequacy in iodine intake in the studied population. Iodine excess could be a possible risk factor for CH, but there were findings, such as lack of correlation between maternal MIC and UIC, and the median neonatal UIC, which was similar in the two groups, so, drawing conclusions should be done with some caution and requires further studies. (Pol J Endocrinol 2010; 61 (4): 371-376)