Endocrine Abstracts

Iodine deficiency is the main cause of preventable mental retardation in children. Urinary iodine excretion is a marker of recent iodine intake and is used to monitor the iodine status of population. Iodine excretion in Lithuanian schoolchildren was previously investigated in 2001. The main objective of this study was to evaluate iodine excretion in children, ages 6–12, living in Vilnius, Lithuania.

Methods

Urine samples were collected from June 2019 to January 2021 at 3 outpatient clinics during “NATRIJOD” – a national program conducted to evaluate sodium and iodine status in Lithuania. Parents signed informed consent forms. Questionnaires about the child’s gender, age, height, dietary habits, use of medications and dietary supplements were collected. Urinary iodine was measured spectrophotometrically by a method based on the Sandell–Kolthoff reaction. The method was approved by the Ensuring the Quality of Urine Iodine Procedures quality assurance program. Urinary creatinine was measured enzymatically by Architect (Abbott, USA) analyser. Urinary iodine concentration (UIC, µg/l) was measured in spot urine samples and estimated 24-hour urinary iodine excretion (UIE, µg/day) was calculated dividing UIC by creatinine and multiplying by expected 24-h creatinine excretion referenced from values of German children with the respective gender and height.

Results

Data of 117 subjects were analysed. Median UIC was 214.68 µg/l and median UIE was 128.92 µg/day. 69.2% of children had UIE within the recommended range. 30.8% of participants had iodine deficiency (UIE <100 µg/day) with a higher rate among girls (40.7%) compared to boys (22.2%) (P = 0.030). 37.8% of 6–7 year-olds, 33.3% of 8–9 year-olds and 22.7% of 10–12 year-olds had iodine deficiency. Median UIE in 6–7 year-olds and in 8–9 year-olds was lower compared to children aged 10–12 (respectively 121.54 µg/day vs 173.15 µg/day, P = 0.049 and 124.23 µg/day vs 173.15 µg/day, P = 0.008). Iodine deficiency rate in children with no diet restrictions was lower than in those who had diet restrictions (25.8% vs 55.0%, P = 0.010). UIE in children who mainly ate home-cooked food was higher compared to those who ate at school or processed food from stores (137.61 vs 99.71 µg/day, P = 0.011).

Conclusion

Compared with the data from 2001 the iodine intake of schoolchildren has increased. However, a considerable portion of children remain at risk of iodine deficiency. Continued monitoring of iodine intake using 24-h urine samples is needed to ensure that the actual iodine intake of schoolchildren is sufficient.