Evolution of thyroid function in patients with covid-19 related atypical thyroiditis

ABSTRACT

Patients with Covid-19 frequently develop atypical thyroiditis coexisting with non-thyroidal illness syndrome (Muller et al LancetD& E 2020). We analysed thyroid dysfunction 1) in relation to Covid-19 disease severity;2) observing its evolution over time. Baseline assessment of 179 patients hospitalised in sub-intensive care units for Covid-19 disease, without known history of thyroid dysfunction or amiodarone therapy, with thyroid function and inflammatory markers measured at hospital admission. Thyroidultrasound (thyroid-US) and thyroid autoantibodies measurement were performed in 65 patients after they became SARS-CoV-2 negative, of whom 14 were also studied with radioisotope thyroiduptake (99mTc or I123) since showing focal-hypoechoic-areas. 46 patients were re-evaluated at 6 months of follow-up. Patients on steroid treatment started before hospitalization (N = 62) were excluded due to its lowering effect on TSH. At baseline 11/117 patients (9.4%) had thyrotoxicosis (low TSH and/or high FT4);23/117 (19.7%) had low TSH and required a more intensive oxygen support during hospitalization (P = 0.02). TSH positively correlated with lymphocyte count (P < 0.01). FT3 correlated negatively with length of hospitalization (P = 0.04) and death rate (P = 0.03). Only 7.7% patients had detectable TgAb/TPOAb and none TRAb. Thyroid-US showed focal-hypoechoic-areas in 28% patients, of whom thyroid-uptake was focally-reduced in 57%, diffusely-reduced in 14% and normal in 28%. Importantly, focalhypoechoic-areas were more frequent among patients with baseline low TSH compared with normal TSH (P = 0.03). Furthermore, patients with focal-hypoechoic-areas had higher baseline FT4 (P = 0.02) and IL-6 (P = 0.02) than those without. Thyroid function and inflammatory markers had normalized at 3 months and remained normal thereafter. At 6 months focalhypoechoic-areas persisted in the majority of patients, often reduced in size;thyroid-uptake was repeated in 8 patients and resulted increased in 7 (87.5%). Thyroid dysfunction during moderate-to-severe Covid-19 disease was mild and transient and correlated with increased death rate and length of hospitalization;low TSH correlated with lymphopenia and was associated with increased need of oxygen support during hospitalization. Focal-hypoechoic-areas at thyroid-US persisted up to 6 months in nearly 1/3 of patients and correlated with thyroid and inflammatory parameters at hospital admission, confirming a key role of thyroiditis in Covid-19 related thyroid dysfunction;long-term effects are unknown.