Furthermore, considering the strength of the effects of TSH and fT3 on lymphocyte counts in the multivariable model, it is likely that thyroid function is only one of the many contributors to lymphopenia in COVID-19, rather than playing a dominant role, given the evidence of expression of the entry receptor of SARS-CoV-2, ACE2, in various human tissues (14). Here, ACE2 is linked to lymphopenia.