The distribution of fasting plasma concentrations of PCSK9 in the Dallas Heart Study (n = 3138) excluding individuals on statins (97 women and 117 men) in all subjects (A), in men only (B; n = 1392), and in women only (C; n = 1746). Levels of PCSK9 were measured using a sandwich ELISA in plasma samples obtained after an overnight fast, as described in Subjects and Methods. Significant differences were observed between men and women after adjustment for age, ethnicity, BMI, diabetes, and plasma levels of LDL-C, HDL-C, and triglycerides (P < 0.0001).