GDF15 and cancer: Several proposals have been put forward to explain why appetite might be suppressed in the early stages of chronic illness, ranging from increases in resistance to appetite-stimulating hormones,28 increased levels of inflammatory cytokines,29 and high levels of other mediators such as growth differentiation factor 15.30 Plasma concentrations of the latter are increased in chronic inflammatory disease, most subtypes of cancer, and cardiovascular and kidney disease, and several longitudinal studies have shown it to be independently associated with decreases in muscle mass and muscle strength.30