PCB126 exposure stimulates the mRNA expression of steroidogenic genes—such as Steroidogenic Acute Regulatory Protein (STAR), Hydroxy-Delta-5-Steroid Dehydrogenase 3 Beta (HSD3B), and Cytochrome P450 Family 19 Subfamily A Member 1 (CYP19A1)—in chicken ovarian follicles, leading to elevated local estrogen level, a key feature of endometriosis[4,49]. The gene discussed is STAR; the disease is endometriosis.