Viral infections that alter estrogen levels during pregnancy may contribute to the etiology of cryptorchidism.

Cryptorchidism is as common as type 2 diabetes or celiac disease. Boys with congenital cryptorchidism are at increased risk of infertility and testicular cancer. Zika syndrome, which affects pregnant women, is associated with a high incidence of undescended testes in the infant, accompanied by epididymal anomalies. Zika and influenza virus infections during pregnancy trigger a strong anti-inflammatory immune response and elevated estradiol levels. Elevated estradiol and α-fetoprotein in syncytiotrophoblasts from women who have given birth to cryptorchid boys are indicative of increased estradiol levels in the fetus. Here, I present a hypothesis that hypogonadotropic hypogonadism, cryptorchidism, and retarded epididymal development may be due to elevated fetal estradiol levels caused by viral infection during pregnancy.