TNF and leiomyoma: Progesterone regulates cytokine production, such as tumor necrosis factor (TNF-α) and interleukin 6 (IL-6) [22]; enhances angiogenesis through vascular endothelial growth factor (VEGF); and promotes extracellular matrix deposition by activating Activin A [22], transforming the growth factor beta (TGF-β), and EGF pathways in leiomyoma tissue [20] (Figure 1).