CYP7A1 and vitamin D deficiency: The three mechanisms: (i) calcitriol (1,25(OH)D) driving INSIG/SREBP mediated feedback [168]; (ii) calcidiol (25(OH)D) suppressing HMGCR activity [171]; and (iii) VDR inducing CYP7A1 activity [170,172] are all consistent with the observation that vitamin D deficiency elevates total cholesterol and LDL-C and with the observation that vitamin D supplementation suppresses total cholesterol and LDL-C.