GPER1 and postmenopausal osteoporosis: 17β-estradiol deficiency is one of the main causes of postmenopausal osteoporosis, which can be treated by 17β-estradiol to protect osteoblasts by inducing mitophagy via the G protein-coupled receptor 30-extracellular regulated protein kinases 1/2 (ERK1/2) signaling pathway, however the protective effect could be abolished when the cells were pretreated with G15, a selective G protein-coupled receptor 30 antagonist 116.