Other genital anomalies are common (eg severely curved penis, undescended testis). The phase of penis development during which the maldevelopment occurs is driven by androgens, and hypospadias can be regarded as a mild form of incomplete masculinization of the male embryo.
Exogenous hormones, such as anti-androgens cause hypospadias. The defect results from incomplete masculinization of the male genitals, which can be mimicked with prenatal rats exposed to anti-androgens in laboratory conditions. Scientists in Europe have established that humans are currently exposed to sufficient levels of environmental pollutants, which under laboratory conditions can produce declines in sperm count and other reproductive problems in test animals. The role of oral contraceptives has also been considered.