Are Thyroid Functions Affected in Multisystem Inflammatory Syndrome in Children?

Objective: Multisystem inflammatory syndrome in children (MIS-C), associated with Coronavirus disease-2019, is defined as the presence of documented fever, inflammation, and at least two signs of multisystem involvement and lack of an alternative microbial diagnosis in children who have recent or current Severe acute respiratory syndrome-Coronavirus-2 infection or exposure. In this study, we evaluated thyroid function tests in pediatric cases with MIS-C in order to understand how the hypothalamus-pituitary-thyroid axis was affected and to examine the relationship between disease severity and thyroid function. Methods: This case-control study was conducted between January 2021 and September 2021. The patient group consisted of 36 MIS-C cases, the control group included 72 healthy children. Demographic features, clinical findings, inflammatory markers, thyroid function tests, and thyroid antibody levels in cases of MIS-C were recorded. Thyroid function tests were recorded in the healthy control group. Results: When MIS-C and healthy control groups were compared, free triiodothyronine (fT3) level was lower in MIS-C cases, while free thyroxine (fT4) level was found to be lower in the healthy group (p<0.001, p=0.001, respectively). Although the fT4 level was significantly lower in controls, no significant difference was found compared with the age-appropriate reference intervals (p=0.318). When MIS-C cases were stratified by intensive care requirement, fT3 levels were also lower in those admitted to intensive care and also in those who received steroid treatment (p=0.043, p<0.001, respectively). Conclusion: Since the endocrine system critically coordinates and regulates important metabolic and biochemical pathways, investigation of endocrine function in MIS-C may be beneficial. These results show an association between low fT3 levels and both diagnosis of MIS-C and requirement for intensive care. Further studies are needed to predict the prognosis and develop a long-term follow-up management plan.