The National Heart, Lung, and Blood Institute GOLDN study, described in detail in previous publications [9 (link), 10 (link)], was designed to identify genetic determinants of lipid response to treatment with 160 mg of micronized fenofibrate once a day for three weeks. Briefly, Caucasian families with at least 2 siblings were recruited from the genetically homogeneous centers of the National Heart, Lung, and Blood Institute Family Heart study in Minneapolis, MN, and Salt Lake City, UT. Participants were asked to discontinue the use of lipid-lowering agents for at least 4 weeks, to fast for at least 8 hours prior to study visits, and to abstain from alcohol for at least 24 hours prior to study visits. The study protocol was approved by Institutional Review Boards at the University of Minnesota, University of Utah, and Tufts University/New England Medical Center.