Inhibition of thyroxine transport into cultured rat hepatocytes by serum of nonuremic critically ill patients: effects of bilirubin and nonesterified fatty acids.

We investigated bilirubin and oleic acid as causes of low plasma T3 in nonuremic critically ill patients with gross changes in serum thyroid hormone levels (T4, or = 0.45 nmol/L) and elevated bilirubin concentrations (> or = 33 mumol/L). Iodide production from [125I]T4 was inhibited by 42% when rat hepatocytes in primary cultures were incubated with 10% serum from these patients. The mean serum concentration of albumin was reduced by 41%, while the concentrations of bilirubin and nonesterified fatty acids (NEFA) were increased by 2022% and 115%, respectively, in the patients. The molar ratios of bilirubin/albumin and NEFA/albumin in the patients were 0.42 and 3.18, respectively. Addition of oleic acid (50-400 mumol/L) and bilirubin (3-130 mumol/L) to 10% normal human serum (albumin, 70 mumol/L; NEFA, 54 mumol/L; bilirubin, 1.1 mumol/L) progressively inhibited the production of iodide by rat hepatocytes. The decreased iodide production was presumed to be caused by inhibiti...