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BACKGROUND: Although it is generally acknowledged that exposure to iodine contrast agents can interfere with thyroid function, little is known about the incidence of iodine-induced hypothyroidism in young children (younger than the age of 4 years). STUDY OBJECTIVES: This was a retrospective cohort study to estimate the incidence rate of detected hypothyroidism in a US-based general population of pediatric patients exposed to an iodinated contrast agent. SETTING: The study was conducted in Kaiser Permanente Northern California, an integrated health care delivery system. STUDY POPULATION: This study included 2320 pediatric patients younger than 4 years of age who had a diagnostic procedure with an iodinated contrast agent during years 2008 to 2016. RESULTS: Among 2320 young children who met our study criteria, we identified 34 who met the initial criteria to be a case of hypothyroidism. The incidence density ratio for all hypothyroidism in iodine contrast agent-exposed patients was 1.33 per 1000 person months (95% confidence interval, 0.9-1.8). Most cases appeared to have subclinical hypothyroidism. The rate was higher for the probably iodine-induced cases (0.90 per 1000 person months) compared with cases with a possible alternate etiology (0.43 per 1000 person months), for males compared with females, and among children who had a heart catheterization compared with those with a computed tomography scan. It was also highest among the youngest children (younger than 3 months old), and decreased with increasing age. DISCUSSION: Our finding of hypothyroidism in young children exposed to iodine contrast agents (1.33 per 1000 person months 95% confidence interval, 0.9-1.8) is broadly consistent with the sparse literature on this outcome.
Jick et al. (Tue,) studied this question.