Interestingly, for Kallmann syndrome, five different genes were found to cause cryptorchidism, each of which is located on separate chromosomes: PROK2 on chromosome 3 (48), SEMA3A on chromosome 7 (53), CHD7 on chromosome 8 (31), PROKR2 on chromosome 20 (48), and ANOS1 on X chromosome (23). Here, PROKR2 is linked to Kallmann syndrome.