Xiao Li is a handsome young man, 27 years old this year, just at the age of marriage, but Xiao Li does not dare to fall in love, into the examination room of the clinic, only to know his unspeakable secret – his scrotum is empty, bilateral testicles are hidden in the groin, and delayed to descend into the scrotum. This condition, medically known as “cryptorchidism”, is a common variation in testicular position during male development. It is generally believed that if the testicles do not descend to the scrotum within 6 weeks after birth in full-term babies and within 3 months after birth in premature babies, it can be judged as “cryptorchidism”, or “incomplete testicular descent”, which can occur on the left or right side alone, or both sides at the same time. In these patients, the testicles may be located in many different places, either in the inguinal canal or in the abdominal cavity. Patients usually have no obvious symptoms and mainly present with a hollow scrotum on the affected side. However, some patients may present with localized painful symptoms if complications such as inguinal hernia or cryptorchid torsion occur. In normal human, the testes should descend to the scrotum at the 28th to 35th week of embryonic development, which is of great importance in human evolution. This is because the scrotum provides the testes with the most comfortable temperature for spermatogenesis and development. The fleshy membrane layer under the scrotal skin can reflexively stretch and contract with the change of external temperature to regulate the temperature inside the scrotum, so the normal human scrotal temperature is about 2℃ lower than the body temperature, which is necessary for the normal development of testes and normal sperm production function after birth. The causes of cryptorchidism are many, endocrine, genetic and mechanical factors can affect the testicles to stay on the way of descent and form cryptorchidism, among which endocrine factors are the main cause. During fetal growth, the lack of sufficient maternal gonadotropin will affect the power effect of the descending testes, thus leading to incomplete testicular descent. What are the adverse effects of a cryptorchidism patient whose testicles are located outside the scrotum in the abdomen or groin for a long time? Most commonly, there are two aspects. On the one hand, the temperature outside the scrotum is not suitable for testicular development, which will lead to the development of spermatogenic tubules and spermatogenic dysfunction, affecting the quality of male semen and greatly increasing the chance of men suffering from infertility. On the other hand, the local temperature, blood flow changes and endocrine changes outside the scrotum may lead to malignant changes in the testes. Some studies have shown that the chance of testicular tumors in cryptorchidism patients is 21-53 times higher than normal people, and the higher the location of cryptorchidism, the higher the incidence of malignant changes. Once cryptorchidism is diagnosed, it should be treated as early as possible. According to clinical experience, if the testicle still has not descended into the scrotum after 6 months of birth, the chance of self-descension is already very small, and it is time to seize the treatment opportunity and start treatment. At present, the clinical treatment for cryptorchidism includes medication and surgery. The most common treatment is human chorionic gonadotropin (HCG). There are two kinds of usage: one is the small dose method, injecting 500 IU of HCG into the muscle every day for 3-4 weeks, and the total dose is 10,000-15,000 IU, which is suitable for use during childhood; the other is the large dose method, injecting 3,000 IU into the muscle every other day for 3-4 times, which is better during puberty. If no effect is seen after a course of treatment, it is not advisable to repeat the use, because the use of HCG can have certain side effects, such as premature sexual maturity, premature closure of bone scale causing dwarfism.