Age- and body surface area-specific ultrasound percentile charts for thyroid volume in Polish school-aged children: comparison with European cohorts.

OBJECTIVE: To establish age- and body surface area (BSA)-specific ultrasound percentile charts for thyroid volume (Tvol) in Polish school-aged children born after the introduction of mandatory iodine prophylaxis, and to compare these values with previous national, WHO, and recent European reference data. DESIGN: Nationwide cross-sectional analysis of iodine-monitoring data. Methods: The source database contained 10,456 screening records from the National Program for the Elimination of Iodine Deficiency in Poland. After hierarchical exclusions, 3,170 children aged 6-13 years with valid thyroid-volume data were included in the age-specific analysis; 2,843 children with complete anthropometric data were included in analyses requiring BSA. Age- and BSA-specific percentile curves (P3-P97) were generated, and multivariable linear regression was performed to identify independent predictors of Tvol. RESULTS: Median urinary iodine concentration (UIC) exceeded 100 µg/L across all age groups, confirming iodine sufficiency at the population level. Median Tvol increased with age from 2.7 to 7.4 mL in girls and from 2.8 to 6.8 mL in boys. The 97th percentile increased from 4.5 to 12.9 mL in girls and from 4.3 to 13.6 mL in boys. BSA was the strongest independent predictor of Tvol, followed by age. Compared with WHO 2004 reference values, the proposed percentiles were consistently higher and closely aligned with recent European data. CONCLUSIONS: This study provides population-specific ultrasound percentile charts for thyroid volume in iodine-sufficient Polish children. These charts complement existing WHO and European references and may improve the interpretation of pediatric thyroid ultrasound in Poland and comparable Central European populations.