Hypothyroidism and Iodine deficiency in children on chronic parenteral nutrition

BACKGROUND AND OBJECTIVES: Iodine is an essential trace element for maintenance of normal thyroid function. Normal thyroid function is a prerequisite for neurocognitive development and growth in children. In the United States, iodine is not routinely added as a trace element in parenteral nutrition (PN). Our objective was to determine the prevalence of iodine deficiency and hypothyroidism in children on chronic PN. METHODS: This was a cross-sectional study of children <17 years of age and using PN for >6 months at a tertiary children's hospital. Primary outcomes were spot urine iodine concentration (UIC), serum thyrotropin, and free thyroxine levels. RESULTS: Twenty-seven patients were identified (74% male). The median age at screening was 48 months (range: 7-213 months). The median duration on PN was 27 months (range: 11-77 months). Seventeen out of 20 patients (85%) were iodine deficient (spot UIC <100 μg/L), whereas 11 out of 20 patients (55%) were severely iodine deficient (spot UIC <20 μg/L). The prevalence of acquired hypothyroidism (elevated thyrotropin, low free thyroxine, and UIC <100 μg/L) was 33% (n = 8). None of the children with hypothyroidism screened for autoimmune thyroiditis had positive test results. There was no statistically significant association between duration of PN use and development of iodine deficiency (P = .08) or hypothyroidism (P = .96). CONCLUSIONS: Children on chronic PN are at risk for developing iodine deficiency and resultant hypothyroidism; hence, these children should be screened for these outcomes. Further studies are needed to define the temporal onset of iodine deficiency and timing to thyroid dysfunction related to PN.