It is a major morphogenic regulator of the outgrowth of the GT mainly through the regulation of cell cycle progression [6,26]. A significant decrease in mRNA expression of the SHH and PTCH1 genes was found in boys with proximal hypospadias compared with boys without hypospadias [27]. Shh expression has been detected in the urethral plate in the developing GT of guinea pigs. The gene discussed is SHH; the disease is hypospadias.