All-cause and disease-specific mortality and morbidity in patients with congenital hypothyroidism treated since the neonatal period: a national population-based study.

Context: Little is known about the long-term health of patients treated for congenital hypothyroidism since the neonatal period.

Objective: To evaluate the causes of mortality and comorbidity in a population-based registry of young adult patients.

Design, Setting, And Participants: All 1772 eligible patients diagnosed during the first decade after the introduction of neonatal screening in France participated in the study. Follow-up data on vital status were available, in May 2010, for 99.5% of the patients. Completed questionnaires were obtained from 1202 of the selected patients.

Main Outcome Measures: All-cause and cause-specific mortality and comorbidity.

Results: All-cause mortality in the congenital hypothyroidism (CH) patients was slightly higher than expected on the basis of year, age, and sex (standardized mortality ratio [SMR] 1.24, 95% CI: 0.81-1.82). SMRs for each category of underlying cause of death showed mortality due to diseases of the central nervous system (SMR 5.22, 95% CI: 1.68-12.17) and congenital malformations (SMR 3.15, 95% CI: 1.86-6.49) to be significantly higher than expected in the CH patients. The risk of developing an associated chronic disease in the 1202 patients who completed the questionnaire was twice that for the reference population (odds ratio 2.0 [1.32-3.03]). Neurologic or mental diseases and congenital malformations were the most frequent (odds ratios 2.54 [1.12-5.86], 4.18 [1.27-13.76], and 4.36 [1.24-15.34], respectively). Overall, mortality and morbidity were not affected by sex, disease severity, cause of CH, or adequacy of treatment.

Conclusion: Prognosis has improved considerably, but a few patients diagnosed during the first 10 years of screening in France nonetheless displayed comorbidity and mortality due to various neurodevelopmental disorders and associated malformations. These results reveal a continuing need for improvements in care and studies to provide knowledge about the full spectrum of the disease and the mechanisms underlying these developmental abnormalities.