Fasting serum bile acid levels in the primary hyperlipoproteinemias.

A newly developed radioimmunoassay specific for conjugates of cholic acid (CCA) was used to measure the fasting serum levels of these bile acids in 233 patients with primary hyperlipoproteinemia classified as type IIa, IIb, III, IV, or V hyperlipoproteinemia as well as in 80 healthy control subjects. Subjects with type IIa hyperlipoproteinemia had significantly lower levels of CCA (0.9 plus or minus 0.06 muM, mean plus or minus SE) than did healthy controls (0.50 plus or minus 0.08 muM). Patients with type IIb, III, IV, and V hyperlipoproteinemia had values similar to those of the control group. The abnormally low fasting value of CCA in type IIa patients is considered to reflect decreased secretion of bile acid into the intestine in such patients, who are known to have defective bile acid synthesis rates and decreased bile acid pool sizes.