To investigate the role of DEC1 in postmenopausal osteoporosis, we used the two genotypes of mice (Dec1+/+ andDec1−/−) to establish an ovariectomy model and found that the bone loss was significantly lower inDec1−/− ovariectomy mice than inDec1+/+ ovariectomy mice. This evidence concerns the gene BHLHE40 and postmenopausal osteoporosis.