For example, in two previous studies that included testicular samples from patients with Klinefelter syndrome, CYP11A1 in one and the steroidogenic acute regulatory protein (StAR, i.e. the initiator of steroidogenesis catalyzed by CYP11A1) in the other, were expressed in all Leydig cells, while INSL3 was not (9, 11). The gene discussed is INSL3; the disease is Klinefelter syndrome.