GDF15 and idiopathic pulmonary fibrosis: The expression of the GDF15 protein is significantly increased in both the circulation and tissues of patients suffering fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF), cardiac fibrosis, and systemic sclerosis (Lambrecht et al. 2014; Rochette et al. 2021; Radwanska et al. 2022).