Low sperm density is a common cause of decreased male fertility and may be caused by the following: 1. Low testicular spermatogenic function. Congenital testicular spermatogenic dysfunction, chromosomal abnormalities, and AZF microdeletions can lead to oligospermia or even severe oligospermia. Acquired damage to testicular function, such as cryptorchidism, testicular trauma or testicular torsion after treatment, varicocele, and the damaging effects of various radiochemicals on the testicles, can all cause low sperm density. 2. Obstructive factors, epididymitis causing poor epididymal drainage and partial obstruction of the ejaculatory duct opening, can all cause poor sperm discharge and low sperm density. 3. Endocrine factors, various factors Insufficient secretion of testosterone caused by various factors can also cause low sperm density.