Many men feel that their semen volume is low during intercourse and wonder if they have a disease that could affect their fertility. Therefore, they are a little worried and want to know what are the causes of low semen, so the following is a brief introduction to the causes of this problem. First of all, we need to know that a healthy and mature male, the amount of semen discharged each time is generally 2-6 ml. If the amount of semen varies slightly, it will not affect the number of sperm. This means that less semen sometimes does not necessarily mean less sperm. It is only when the amount of semen ejaculated is less than 1 ml that it is considered too little semen. So what are the causes of low semen? Causes of cryptorchidism: Cryptorchidism is one of the major causes of semen quality. About 60% of patients with unilateral cryptorchidism are infertile, so if sperm density is low and cryptorchidism is present, early treatment is necessary. Causes of chromosomal abnormalities: Low sperm volume may be due to chromosomal abnormalities. Chromosomal abnormalities have serious effects on sperm density, activity rate and morphology. Causes of endocrine abnormalities: Endocrine abnormalities can also lead to low sperm volume. Normal sperm production function in men depends on the normal function of the hypothalamic-pituitary-gonadal axis, and any one of these links is impaired, which will affect the sperm production function. Other diseases such as thyroid and adrenal gland diseases can also affect the function of the gonad and cause oligospermia. Caused by varicocele: varicocele is the main cause of low sperm quantity. When varicocele raises the local temperature of the testes, the vasoactive substances increase, thus affecting the spermatogenic function of the testes, but the degree of varicocele is not proportional to the quality of sperm. Caused by autoimmunity: Low sperm quantity may be caused by autoimmunity. Reproductive immunology research found that male autoimmunity can affect fertility, and anti-sperm antibodies can affect sperm production and delivery. Caused by high temperature of cryptorchid: There are also high scrotal temperature, radiation injury, chemical drugs and drug effects can cause oligospermia. Caused by urinary system infection: Urinary system infection also has an effect on sperm volume. Chronic infection of the accessory genital glands can affect various laboratory indicators in semen. Damage to the vas deferens: Damage to the vas deferens caused by seminal vesicle tumors or cysts, urethral stricture, urethral diverticulum or genital tract surgery can also reduce semen volume.