Molecular observations support a crucial role for PROK2 in the pathophysiology of cryptorchidism with impaired PROK2/CHD7/FGFR1/SPRY4 gene expression inducing LH deficiency as controlled by the regulators EGR4 and PITX1.Second, unilateral cryptorchidism is a bilateral disease and a serious andrological problem. The gene discussed is SPRY4; the disease is cryptorchidism.