<prompt> In Klinefelter syndrome, all are true exceptNegative feedback on FSH and LH are lostDecreased Androstenedione levelsHypoplastic male external genitaliaMost common cause of primary testicular failure  <response>: In Klinefelter syndrome, since testosterone levels are decreased, negative feedback on FSH and LH is lost.Increased FSH stimulates Leydig cells, thereby causing elevated levels of Androstenedione. 