In vivo work has focused on the vitamin D receptor (expressed in muscle and bone) as a possible mechanism relating to the atrophy of both tissues, with a recent study documenting a reduction in muscle mass and function upon deletion of the vitamin D receptor in myocytes.63 An earlier study, again in rodents, also showed that vitamin D deficiency induces muscle wasting and decreased muscle gene markers,58 suggesting a role of vitamin D in myogenesis, which may account for the previous findings. Here, VDR is linked to vitamin D deficiency.