Fig. 1.

Conditions associated with an increased FGF21 expression. FGF21 increases in four main circumstances: a) Mitochondrial diseases; b) oxidative stress, c) physical stress situations, such as ketogenic diets, free fatty acids release, lactation, treatment with exogenous growth hormone, and moderate to vigorous exercising; d) pathological physical stress such as obesity, anorexia nervosa, skeletal muscle autophagy deficiency, critical illness, hypothermia, amino acid deprivation, undernutrition, and diabetic nephropathy.