Increased risk for hypothyroidism associated with carbon monoxide poisoning: a nationwide population-based cohort study

Carbon monoxide poisoning (COP) may cause injuries to the central nervous and endocrine systems, which might increase the risk of developing hypothyroidism. We wanted to evaluate the association between COP and the risk of developing hypothyroidism because epidemiological data on this potential association are limited. We conducted a nationwide population-based cohort study using the Nationwide Poisoning Database and identified 24,328 COP subjects diagnosed between 1999 and 2012. By matching the index date and age, we selected 72,984 non-COP subjects for comparison. Subjects with thyroid diseases and malignancy before 1999 were excluded. We followed up the two groups of subjects until 2013 and compared the risk of developing hypothyroidism. COP subjects had a significantly higher risk for hypothyroidism than non-COP subjects (adjusted hazard ratio [AHR]: 3.8; 95% confidence interval [CI]: 3.2-4.7) after adjusting for age, sex, underlying comorbidities, and monthly income, and the AHR was particular higher in subjects with diabetes mellitus, hyperlipidemia, and mental disorder. The increased risk was highest in the first month after COP (AHR: 41.0; 95% CI: 5.4-310.6), and the impact remained significant even after 4 years. In conclusion, COP was associated with an increased risk for hypothyroidism. Further studies regarding the underlying mechanisms are warranted.