In a study performed by Miyashita-Ishiwata et al., the researchers found that under hypoxic conditions, HIF-1 was expressed in both leiomyoma and normal myometrium; however, secretion of HIF-1 target proteins, such as VEGF-A, ET-1, and ADM was found only in leiomyomas [24]. This evidence concerns the gene EDN1 and leiomyoma.