CD4 and COVID-19: Peeters et al. [15], in a classical study of thyroid hormone changes during critical illness, enrolled 451 patients with thyroid hormones measured at days 1, 5, and 15 and the last day of their ICU admission, and described an increase in peripheral thyroid hormones in surviving patients, whereas thyroid hormones in patients who died decreased (15), similarly to what occurred in preliminary studies involving COVID-19 patients [16,17] This is in line with previous studies suggesting that an increase in TSH drives the rise in T4, and thus points to the onset of recovery [18,19].