LDL receptor studies in children with heterozygous familial hypercholesterolemia (FH): measurement of sterol synthesis in blood lymphocytes.

Sterol synthesis was measured in lymphocytes from 48 members of 10 families with familial hypercholesterolemia (FH) under three sets of conditions. First the synthesis of LDL receptors and sterols were maximally stimulated by incubation of lymphocytes in lipoprotein-deficient serum. Secondly sterol synthesis was suppressed by the addition of LDL and thirdly sterol synthesis was maximally suppressed by the addition of 7-ketocholesterol. In five of the ten families LDL suppression of sterol synthesis in FH heterozygotes was only about half of the LDL suppression in normals. In four families, however, there was a considerable overlapping of LDL suppression in FH heterozygotes and normals. Finally in one family LDL suppression was strictly normal in FH heterozygotes who thus appear to have a different type of FH not involving an impaired LDL receptor function.