Regulates food intake, energy expenditure and body weight in response to metabolic and toxin-induced stresses. Binds to its receptor, GFRAL, and activates GFRAL-expressing neurons localized in the area postrema and nucleus tractus solitarius of the brainstem. It then triggers the activation of neurons localized within the parabrachial nucleus and central amygdala, which constitutes part of the 'emergency circuit' that shapes feeding responses to stressful conditions (PubMed:28953886, PubMed:28846097, PubMed:28846099, PubMed:28572090, PubMed:23468844, PubMed:29046435). On hepatocytes, inhibits growth hormone signaling (PubMed:28572090). Homodimer; disulfide-linked (By similarity). Interacts with GFRAL; ligand of GFRAL which mediates GDF15 internalization and cellular signaling through interaction with RET (PubMed:28846098, PubMed:28846099). Highly expressed in liver (PubMed:10779363, PubMed:28572090, PubMed:29046435). Detected in plasma (at protein level) (PubMed:28572090, PubMed:29046435). Expressed by cardiomyocytes, expression is highly increased in heart diseases (PubMed:28572090). Also detected in subcutaneous fat (PubMed:28572090, PubMed:29046435). At postnatal day 3 (P3), detected in heart and plasma, expression decreases with lower levels at P7 to, at least, P13. Expression is up-regulated by obesity. Mutants weight more, have increases adiposity associated with increased spontaneous food intake and exhibit reduced basal energy expenditure and physical activity (PubMed:23468844). Female mutants exhibit some additional alterations in reduced basal energy expenditure and physical activity (PubMed:23468844). At behavioral level, they exhibit a task-dependent increase in locomotion and exploration and reduced anxiety-related behaviors across tests. Their spatial working memory and social behaviors are not affected. They form an increased association with conditioned stimulus in fear conditioning testing and also display significantly improved prepulse inhibition (PubMed:28081177). Belongs to the TGF-beta family.