In other genes, such as DLK-1, involved in fibrosis [36], the expression level was increased, and COL1A1, a gene involved in collagen synthesis and fibrosis, which is typically increased in the presence of a functional IGF-IR [37, 38], was decreased after siIGF-IR further indicating that IGF-IR may play an important role in fibrosis in uterine leiomyomas. This evidence concerns the gene COL1A1 and uterine corpus leiomyoma.