GDF15 and COVID-19: Similarly, recent studies report that GDF15 levels, a member of the transforming growth factor-β (TGF-β) superfamily, are increased in COVID-19 patients who require hospitalization, and its levels are associated with viremia, hypoxemia, and worse clinical outcome (Notz et al., 2020; Myhre et al., 2020; Luis García de Guadiana et al., 2021).