The increments in serum concentrations of unconjugated bilirubin and free fatty acids (FFA) were measured 24 and 48 h after reduction of the caloric intake (400 cal/day) in 17 patients with Gilbert's syndrome (GS) and in 12 healthy control subjects. In males, both normal and with GS, the rise in serum bilirubin was statistically higher (p less than 0.01) as compared to females. On the contrary, no sex difference was found in FFA concentrations. A linear correlation (p less than 0.01) between bilirubin and FFA serum levels was present in normal males and in patients with Gilbert's syndrome of both sexes. Because bilirubin and FFA partly share a common, bilitranslocase-mediated, hepatic uptake mechanism, data reported support the hypothesis that a bilitranslocase function may be one of the metabolic defects in Gilbert's syndrome.
