LDLR and familial hypercholesterolemia: As such, loss-of-function mutations in LDLR, termed “familial hypercholesterolemia (FH)”, lead to a significantly increased serum LDL cholesterol (LDL-C) levels in patients, with cholesterol concentrations ranging from 350 to 500 mg/dL and 650 to 1000 mg/dL in heterozygotes and homozygotes, respectively.