Thyroid Function Before, During, and After COVID-19
Bernard Khoo, Tricia Tan, Sophie Clarke, Edouard Mills, Bijal Patel, Manish Modi, Maria Phylactou, Pei Chia Eng, Layla Thurston, Emma Alexander, Karim Meeran, Alexander Comninos, Ali Abbara, Waljit S. Dhillo
Abstract
CONTEXT: The effects of COVID-19 on the thyroid axis remain uncertain. Recent evidence has been conflicting, with both thyrotoxicosis and suppression of thyroid function reported. OBJECTIVE: We aimed to detail the acute effects of COVID-19 on thyroid function and determine if these effects persisted on recovery from COVID-19. DESIGN: A cohort observational study was conducted. PARTICIPANTS AND SETTING: Adult patients admitted to Imperial College Healthcare National Health Service Trust, London, UK, with suspected COVID-19 between March 9 to April 22, 2020, were included, excluding those with preexisting thyroid disease and those missing either free thyroxine (FT4) or thyrotropin (TSH) measurements. Of 456 patients, 334 had COVID-19 and 122 did not. MAIN OUTCOME MEASURES: TSH and FT4 measurements were recorded at admission, and where available, in 2019 and at COVID-19 follow-up. RESULTS: Most patients (86.6%) presenting with COVID-19 were euthyroid, with none presenting with overt thyrotoxicosis. Patients with COVID-19 had a lower admission TSH and FT4 compared to those without COVID-19. In the COVID-19 patients with matching baseline thyroid function tests from 2019 (n = 185 for TSH and 104 for FT4), TSH and FT4 both were reduced at admission compared to baseline. In a complete case analysis of COVID-19 patients with TSH measurements at follow-up, admission, and baseline (n = 55), TSH was seen to recover to baseline at follow-up. CONCLUSIONS: Most patients with COVID-19 present with euthyroidism. We observed mild reductions in TSH and FT4 in keeping with a nonthyroidal illness syndrome. Furthermore, in survivors of COVID-19, thyroid function tests at follow-up returned to baseline.