Steroidogenic Factor 1 (SF-1) is considered an orphan nuclear receptor that belongs to subfamily 5. It was found to be a regulator of steroidogenic enzyme gene expression. Oxysterols are suggested as its ligands. It is expressed in all steroidogenic tissues, including the adrenal cortex, testicular Sertoli cells, and Leydig cells, ovarian theca, hypothalamus, and anterior pituitary. SF-1 plays an important role in adrenal and gonadal development. SF-1 is highly valuable marker to determine the adrenocortical origin of an adrenal mass.