TNFSF11 and cystic fibrosis: There have been conflicting findings regarding the relative concentration of OPG and RANKL in CF compared with DP; thus, further research should be conducted to further establish this relationship.17,26,35,41,53 The discrepancy in AGE concentration could be due to different sample sizes.26,53 The increase of OPG and RANKL in CF relative to HP supports the idea that the RANK-RANKL-OPG pathway is involved in CF.