The protein encoded by STAR plays a key role in the acute regulation of steroid hormone synthesis by enhancing the conversion of cholesterol into pregnenolone. This protein permits the cleavage of cholesterol into pregnenolone by mediating the transport of cholesterol from the outer mitochondrial membrane to the inner mitochondrial membrane. Mutations in STAR are a cause of congenital lipoid adrenal hyperplasia (CLAH, also called lipoid CAH. A pseudogene of STAR is located on chromosome 13.