Abstract
Background: Angiotensin-converting enzyme 2 (ACE2) is a receptor for SARS-CoV-2, expressed in many organs’ cells, including the thyroid gland. Therefore, COVID-19 may influence thyroid gland function. Objectives: In this article, we aimed to investigate the thyroid gland function in COVID-19 patients and compare them to healthy society to indicate whether thyroid hormones level differ in the disease or not. Methods: This is a single-center retrospective case-control, cross-sectional study on 191 COVID-19 patients and 179 non-COVID-19 individuals as the control group. The status of the thyroid hormones was determined in COVID-19 patients and then compared with the control group. Patients in the case group were divided into 2 groups with and without normal thyroid function and were compared with each other in different aspects of COVID-19. Also, we compared thyroid hormone levels in the patient group with different underlying diseases to show the status of thyroid function in COVID-19 infection. Results: Of the 191 COVID-19 patients, 98 (51.3%) were male, and the mean age of patients was 64 ± 15 years. The thyrotropin level was lower in the patient group than in the control group (1.34 ± 1.29 vs. 2.21 ± 1.99; P < 0.001). The T3 status was meaningfully associated with the level of SpO2 (P < 0.05; r = -0.258). The results demonstrated that thyrotropin (P = 0.653), T3 (P = 0.404), and T4 (P = 0.147) levels were not different in expired and discharged patients. The 2 groups of patients with and without normal thyrotropin levels did not appear significantly different in any aspect of the disease. Conclusions: Thyrotropin level was lower in COVID-19 patients, and the T3 level can predict the SpO2 level. The thyroid gland may be theoretically affected by SARS-CoV-2 infection.