INTRODUCTION: We evaluated whether persistent-positive celiac serology is associated with the risk of hypothyroidism. METHODS: We extracted a cohort of subjects aged 1-80 years with a positive IgA anti-tissue transglutaminase between January 1, 2008, and December 31, 2012, and a repeat anti-tissue transglutaminase test within 6-36 months from a large population-based electronic medical record database. Based on serology tests, we categorized the pediatric (age <21 years) and adult cohorts into normalized or persistent-positive serology groups. All subjects were followed up for incident diagnosis of hypothyroidism from the last serology date up to December 31, 2017. Hazard ratio (HR) along 95% confidence intervals (CIs) were prepared to evaluate the association of celiac serology group with a diagnosis of hypothyroidism, crude, and adjusted for age, sex, and diagnosis of type 1 diabetes mellitus. RESULTS: Among the pediatric cohort (n = 2,687), during a median follow-up of 64 months (interquartile range 48-80), 2.3% (16/681) of the persistent-positive serology group and 1.0% (20/2,006) of the normalized serology group developed hypothyroidism (HR 2.07 [95% CI 1.07-4.44], adjHR 1.77 [95% CI 0.91-3.46]). The rate among the pediatric cohort with an established diagnosis of celiac disease was 3.4% (10/486) vs 1.0% (5/481), HR 2.83 (0.96-8.32). In the adult cohort (n = 1,286), 4.5% (20/442) of the persistent-positive group and 3.9% (33/811) of the normalized serology group developed hypothyroidism (HR 1.13 [95% CI 0.65-1.97]). DISCUSSION: In this retrospective, age-stratified analysis, we report that persistent-positive serology may be associated with the risk of hypothyroidism among the pediatric population. Prospective cohorts are needed to validate our findings.