Growth differentiation factor-15 (GDF-15), also known as macrophage inhibitory cytokine-1 (MIC-1), is a member of the transforming growth factor β (TGF-β) superfamily. In human somatic tissues, physiological GDF-15 expression is low or absent, but elevated GDF-15 levels have been associated with cellular stress, inflammation, metabolic conditions, cancer, and other diseases (Emmerson et al.; Wischhusen et al.). GDF-15 signals through GFRAL (GDNF Family Receptor Alpha Like) and the co-receptor RET, resulting in phosphorylation of RET and activation of signaling via ERK and AKT pathways (Emmerson et al.). Human recombinant GDF-15 has been used in mouse studies (Kim et al.). This product was tested negative for TGF-β activity, a common contaminant of commercial sources of GDF-15 (Olsen et al.). This product is animal component-free (ACF).