ABCA4 and gallstones: Mendelian randomization analysis using 15 independent variants for campesterol suggested a causal effect of lower plasma campesterol level on higher gallstone risk (“Methods”; β = −0.70, P = 7.2 × 10−8; Fig. 5b, c).  ABCG5 and ABCG8 together encode a heterodimeric ATP-binding cassette transporter that facilitates secretion of cholesterol and non-cholesterol sterols in the intestine and bile.