GHRL and Osteopenia: Xiao et al. observed on significant difference in four ghrelin level-related single nucleotide polymorphisms (SNPs) between the AIS osteopenia and control groups, which indicated that abnormally high ghrelin may not result from gene variations, while dysregulation of ghrelin/receptor activator of nuclear factor-kappa beta ligand (RANKL)/osteoprotegerin (OPG) pathway may lead to decreased osteogenic ability of osteoblasts and bone marrow stem cells (BMSCs), which may be related to lower bone mass in AIS osteopenia [21].