A child with one testicle is medically called cryptorchidism, or it may be congenital testicular agenesis. Cryptorchidism refers to various causes of testicular descent abnormalities, one side without testicles is one of the side of the cryptorchidism, testicles can not descend to the scrotum, but stay in the inguinal canal, abdominal abdominal cavity. Common causes include: insufficient maternal chorionic gonadotropin secretion, abnormalities of the fetal hypothalamic-pituitary-gonadal axis, androgen receptor deficiency, abnormal development of the inguinal canal, retroperitoneal fibrous adhesions, and spinal cord defects involving the genitofemoral nerve. Testicular development requires a cooler temperature, and if the testes are in the abdominal cavity, as the temperature in the abdominal cavity is relatively high, this will affect the spermatogenic function. Therefore, it is recommended to take your child to the hospital for examination as soon as possible and follow the doctor’s advice if you find that your child has only one testicle. Generally speaking, the testicle may descend on its own within 1 year of age, and if it has not yet descended after 1 year of age, chorionic gonadotropin can be applied for a short period of time. If the testicles have not descended before the age of 2, surgical treatment should be used. Of course, individuals may also be born with testicular agenesis and have only one testicle.