Increased incidence of congenital hypothyroidism in China: an analysis of 119 million screened newborns

Purpose: The incidence of congenital hypothyroidism (CH) in China has increased though no nation-wide epidemiology has reported. To evaluate its trends and explore the possible reasons behind it. Methods: : Data of screened newborns from the Chinese Newborn Screening Information System from 2012 to 2019 was collected. We applied a Bayesian Hierarchical Poisson Regression model, meta-analysis, and several quantitative analyses to estimate incidence or proportion over years. Results: 119,230,553 screened neonates and 56,617 CH cases were collected. The estimated CH incidence increased from 4.01 per 10,000 births in 2012 to 5.77 per 10,000 births in 2019. The average annul growth rate (ARG) of CH incidence for all provinces varied from 0.59% to 20.96%. Incidences of cases with initial TSH concentration of <10 mIU/L rose most rapidly. The results of meta-analysis showed the proportion of permanent CH increased by 0.024% (0.011%, 0.037%) per year. Each one-unit (mIU/L) decrease in TSH cutoffs value was associated with a 2.96% increase in CH incidence. The proportion of premature CH cases in the total number of CH increased from 6.60% to 9.10%, the increase of which was much higher than that of preterm birth rate in the same period. The provincial growth rate of screening coverage and provincial baseline CH incidences showed no significant association with their annual growth rates of CH incidence. Conclusion: CH incidence has substantially increased in China. The slight adjustment of TSH cutoff value, and improvement of screening algorithm for preterm newborn might contribute to such a trend, however, their contribution is limited.