Hypothyroidism associated with triple mortality in patients hospitalized with COVID-19

BACKGROUND: Many conditions have been associated with severe COVID-19 disease. To date, the risk associated with pre-existing hypothyroidism remains unclear. Hypothyroidism affects the innate immune system. Patients with hypothyroidism have higher circulating inflammatory markers, which are associated with increased mortality in COVID-19. A prior study did not find a significant difference in the risk of hospitalization or death in patients with pre-existing hypothyroidism. This study aims to investigate a possible association between pre-existing hypothyroidism and death from COVID-19. METHODS: We performed a retrospective cohort study of adult inpatients diagnosed with SARS-CoV-2 infection in a tertiary, academic referral center in Richmond, Virginia. We analyzed the unadjusted and adjusted association of patients with a past medical history of hypothyroidism and all-cause hospital mortality. We performed adjusted logistic regressions adjusting for age, gender, race, the month at presentation (an adaptation of the health system), and the remaining 30 individual diagnostic categories of the Elixhauser comorbidity index. RESULTS: Fifty-three (8.2%) of the 649 COVID-19 inpatients had hypothyroidism. Patients with hypothyroidism were, on average, 15.3 years older (95% CI 10.3 to 20.4 years). The unadjusted mortality of patients with hypothyroidism was 22.6% compared with 7.4% in patients without hypothyroidism. The unadjusted mortality OR was 3.5 (95% CI 1.7 to 7.2, P=0.001). The adjusted OR for death was 3.6 (95% CI 1.4 to 9.3, P=0.007, abstract figure). The average adjusted mortality was 18.6% for patients with hypothyroidism compared with 7.8% in patients with equivalent age, gender, race, remaining comorbidities, and month of presentation. CONCLUSION: Our results suggest that pre-existing hypothyroidism is associated with a three-fold risk of death in patients hospitalized with COVID-19. There are conflicting reports in the literature on the association between hypothyroidism and severe COVID-19. Earlier descriptive studies did not report rates of thyroid disease in their cohorts. Further research is needed on the pathophysiology and effects of SARS-CoV-2 infection in hypothyroid individuals.