Risk and Course of SARS-CoV-2 Infection in Hypo- and Hyperthyroidism: A Danish Population Based Case-Control and Cohort Study

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is associated with high rates of hospitalization and death. There are no population-based data on risk and course of SARS-CoV-2 infection in patients with hypo- or hyperthyroidism.Methods: We conducted a population based case-control and cohort study using Danish health registries assessing the risk and course of SARS-CoV-2 between 27 th February 2020 and 30 th September 2020 in patients with hypo- and hyperthyroidism. In the case-control analysis, 28∙078 SARS-CoV-2 positive individuals were matched with up to 10 SARS-CoV-2 negative individuals on age, sex, and week of testing. Odds ratios (OR) were obtained using multivariate conditional logistic regression. In the cohort analysis of outcomes, propensity score weighted risks, risk ratios (RR) and risk differences (RD) for death and hospitalization were estimated.Findings: Patients with hypo- or hyperthyroidism did not have an increased risk of contracting SARS-CoV-2 infection [OR hypo = 1∙04 (95% CI 0∙96-1∙12) and OR hyper = 0∙99 (0∙79-1∙23)]. Among infected individuals, there was no association between treatment for hypothyroidism and 30-day mortality [RR 0∙87 (0∙66-1∙19 and RD -1∙2 (-3∙7-1∙3)], whereas the risk of hospitalization was slightly increased [RR 1∙20 (1∙02-1∙40) and RD 4∙1% (0∙2-8∙1)]. Being treated for hyperthyroidism was not associated with 30-day mortality [RR 1∙03 (0∙62-1∙73) and RD 0∙6% (-8∙3-9∙5)] or hospitalization [RR 1∙14 (0∙76-1∙71) and RD 3∙5% (-7∙9-14∙9)].Interpretation: Patients treated for hypo- or hyperthyroidism do not have an increased risk of contracting SARS-CoV-2, and treatment for hypo- or hyperthyroidism is not associated with a worse prognosis of SARS-CoV-2 infection.Funding Statement: None.Declaration of Interests: THB, LH, and JH declare no conflicts of interest. LCL reports participation in research projects funded by Menarini Pharmaceuticals and LEO Pharma, all with funds paid to the institution where he was employed (no personal fees) and with no relation to the current study. All authors have completed the ICMJE conflicts of interest form available at http://www.thelancet.com/for-authors/forms# icmje-coi.Ethics Approval Statement: The institutional data protection board at the University of Southern Denmark and the Danish Health Data Authority have approved the study. According to Danish law,studies based entirely on register data do not require review from an ethics committee.