There is an old Chinese saying, “If you are unfilial, you have no children”, which shows that having children and nurturing the next generation is crucial. Azoospermia, as one of the male infertility diseases, has become the focus of analysis in the field of male science in recent years, and it is not uncommon for azoospermia to cause problems for men, accounting for about 1 to 2 percent of the population of fertile men, which means that one in 50 to 100 men may suffer from azoospermia. At least 30 million men worldwide have been diagnosed with azoospermia. So what exactly is the cause of azoospermia? Why do so many people suffer from azoospermia? 1. What is azoospermia? The term azoospermia refers to the failure to find sperm after centrifugal sedimentation of the ejaculated semen for three consecutive sperm retrievals and microscopic examination. 2.What are the causes of azoospermia? Azoospermia can be divided into pre-testicular causes, testicular causes and post-testicular causes. Pre-testicular causes of azoospermia are congenital abnormalities of the hypothalamus or pituitary gland, or damage to the hypothalamus or pituitary gland caused by acquired surgery, trauma or tumor. This pre-testicular cause is amenable to hormone replacement therapy and most patients can produce sperm with treatment. Testicular causes of azoospermia are due to lesions of the testes themselves, such as congenital cryptorchidism, congenital testicular dysplasia, acquired orchitis, especially mumps orchitis, and some unexplained testicular causes of azoospermia. Testicular azoospermia is more difficult to treat, some patients can be treated with testicular microscopic sperm retrieval for IVF, while some patients cannot get sperm even with testicular sperm retrieval under the microscope, so they can only use sperm from human sperm banks for assisted reproduction treatment. Post-testicular factor is a condition in which the testes can produce sperm normally, but the vas deferens is inaccessible, preventing sperm from being discharged. If the vas deferens is congenitally hypoplastic or congenitally absent, these patients can only be treated by IVF through testicular puncture; if the vas deferens is damaged due to inguinal hernia surgery, syringomyelia surgery or after vasectomy, vasectomy can be performed under the microscope; if the vas deferens is obstructed due to inflammation, the common ones are epididymal obstruction, which can be performed under the microscope. Vasectomy and epididymal anastomosis can be done under the microscope. 3.What are the causes of obstructive azoospermia? (1) For congenital factors, bilateral absence of the vas deferens is a common cause, which is often accompanied by the absence of the seminal vesicles and epididymal dysplasia. (2) For acquired factors, obstruction of the epididymis-vas deferens caused by epididymitis is a common cause of obstructive azoospermia. In addition, ejaculatory duct cysts, calcification, epididymal tuberculosis, and medical injury caused by surgery (such as hernia surgery) are all more common causative factors. 4.What are the causes of non-obstructive azoospermia? (1) Common genetic factors: (1) Creutzfeldt-Jakob syndrome: the karyotype of the patient is 47,XXY; (2) Y chromosome AZF region deletion: the AZF region of the patient is divided into three regions: a, b, and c. The deletion of a or b region shows complete azoospermia, while the testis of the patient with c region deletion can produce a small amount of sperm; (3) congenital hypogonadism: the patient’s performance is significantly reduced in FSH, LH, and T, and no spermatozoa mature. (iii) congenital hypogonadism: patients present with significantly reduced FSH,LH,T and no spermatogenesis maturation. There are other rare, known and unknown genetic factors causing spermatogenic disorders. (2) Common acquired factors: bilateral cryptorchidism, post-pubertal mumps, acquired hypogonadism, and radiotherapy in tumor patients. The above is an introduction to what causes azoospermia in men. Most patients are found to have azoospermia because they are unable to conceive their wives after years of marriage and without contraception, and they come to the hospital for infertility tests. There are many causes of azoospermia in men, and regardless of the cause, it is important to identify and treat it as early as possible.