VDR and sarcopenia: Limited genetic linkage-analysis and Genome-wide association studies identified thyrotropin-releasing hormone receptor (TRHR) gene, the Angiotensin converting enzyme (ACE) gene, α-actinin-3 (ACTN3), ciliary neurotrophic factor (CNTF) gene, myostatin-related genes (MSTN), vitamin D receptor (VDR) gene, and androgen receptor (AR) gene to contribute to muscle aging, muscle strength, and mass with relevance to sarcopenia [11].