Subacute thyroiditis following recovery from COVID-19 infection: novel clinical findings from an Eastern Indian cohort

Abstract

Objective: Recent reports have suggested a link between COVID-19 infection and subacute thyroiditis (SAT). We aimed to describe variations in clinical and biochemical parameters in patients developing post-COVID SAT. Design: Ourswas a combined retrospective-prospective study on patients presenting with SATwithin 3months of recovery fromCOVID- 19 infection, who were subsequently followed up for a further 6 months since diagnosis of SAT. Results: Out of 670 patientswith COVID-19, 11 patients presented with post-COVID-19 SAT (6.8%). Thosewith painless SAT (PLSAT, n=5) presented earlier, had more severe thyrotoxic manifestations and exhibited higher C-reactive protein, interleukin 6 (IL-6), neutrophillymphocyte ratio and lower absolute lymphocyte count than those with painful SAT (PFSAT, n=6). There were significant correlations of total and free T4 and total and free T3 levels with serum IL-6 levels (pall <0.04). No differences were observed between patients with post-COVID SAT presenting during the first and second waves. Oral glucocorticoids were needed for symptomatic relief in 66.67% of patients with PFSAT. At 6 months of follow-up,majority (n=9, 82%) achieved euthyroidism, while subclinical and overt hypothyroidism were found in one patient each. Conclusions: Ours is the largest single-centre cohort of post-COVID-19 SAT reported until, demonstrating two distinct clinical presentations-without and with neck pain-depending on time elapsed since COVID-19 diagnosis. Persistent lymphopaenia during the immediate post-COVID recovery period could be a key driver of early,painless SAT. Close monitoring of thyroid functions for at least 6 months is warranted in all cases.