The hormone 1,25(OH)2D has antiproliferative and pro-differentiating effects in cancer cell lines.[4] It inhibits growth in colorectal cancer cell lines.[5] Epidemiological investigations have consistently shown that low serum levels of 25(OH)D, the precursor to 1,25 (OH)2D, are significantly related to increased risk of both colorectal adenomas and cancer.[6] Given the antineoplastic effects of 1,25 (OH)2D, the regulation of this hormone by FGF-23 may be of importance in colorectal carcinogenesis. The gene discussed is FGF23; the disease is cancer.