when the testis does not produce anti-müllerian hormone the müllerian ducts develop into
Anti-Müllerian hormone AMH is activated by SOX9 in the Sertoli cells of the male fetus.[4] Its expression inhibits the development of the female reproductive tract, or Müllerian ducts (paramesonephric ducts), in the male embryo, thereby arresting the development of fallopian tubes, uterus, and upper vagina.[5][6][7][8] AMH expression is critical to sex differentiation at a specific time during fetal development, and appears to be tightly regulated by nuclear receptor SF-1, transcription GATA factors, sex-reversal gene DAX1, and follicle-stimulating hormone (FSH).[9][10][11] Mutations in both the AMH gene and the type II AMH receptor have been shown to cause the persistence of Müllerian derivatives in males that are otherwise normally masculinized.[12]
Cryptorchidism Cryptorchidism is the absence of one or both testes from the scrotum. It is the most common birth defect of the male genital.[1] About 3% of full-term and 30% of premature infant boys are born with at least one undescended testis. However, about 80% of cryptorchid testes descend by the first year of life (the majority within three months), making the true incidence of cryptorchidism around 1% overall. Cryptorchidism may develop after infancy, sometimes as late as young adulthood, but that is exceptional.