Monorchidism is a congenital absence of one testicle and does not affect fertility if the opposite testicle develops normally.
The cause is unknown, but it may be due to atrophy of the testis during pregnancy, perinatal torsion or embryonic gonadal failure. If you are born with monorchidism, you need to make sure that the testicular tissue is present on the missing side, and that cryptorchidism is not present or is not a possibility.
If the opposite side of the testis is functioning normally, and if there are no other concomitant malformations, no treatment is needed and fertility is not affected. However, if a patient is born with monorchidism, it may lead to infertility if it is accompanied by limited development of the genitals and absence of the vas deferens.
It is recommended that patients born with a single testicle should consult a doctor and follow the doctor’s instructions for examination or treatment.