CYP24A1 and cancer: Alternatively, maintaining higher vitamin D status during the longer period of winter months in higher latitudes may be biologically important for the vitamin D-cancer association; Vieth has hypothesized that sharp declines in serum 25(OH)D in the winter and a lag in the compensating response of cellular hydroxylases involved in vitamin D metabolism (e.g., CYP24 and CYP27B1) could be detrimental in terms of cancer risk [37].