For instance, on the hypothalamus–pituitary–thyroid axis (HPT), they act by lowering TSH secretion, while, peripherally, they reduce the metabolism of TH via deiodinases by reducing the conversion of T4 to T3 and increasing the inactivation of both T4 and T3 [27], thereby possibly contributing to the ESS syndrome often found in COVID-19 patients. This evidence concerns the gene TH and COVID-19.