CCL2 and endometriosis: Considering the importance of MCP‐1, HGF, and IGF‐1 in the development of endometriosis and the inhibitory effect of vitamin D on the expression of these factors in other cell types in different diseases, we proposed a hypothesis that vitamin D may have an inhibitory effect on the development of endometriosis by reducing MCP‐1, HGF, and IGF‐1 expression in peripheral blood mononuclear cells (PBMCs), peritoneal fluid mononuclear cells (PFMCs), and endometrial stromal cells (ESCs) of women with endometriosis compared with non‐endometriotic patients.