1. Sperm production disorders: including azoospermia, oligozoospermia, asthenozoospermia, etc.
2. Diseases of the reproductive organs, such as orchitis, epididymitis, prostatitis, etc., may affect the generation, quality, or transport of sperm.
3. Genetic diseases: Certain genetic diseases, such as Crohn's syndrome and Y chromosome microdeletions, can lead to male infertility or decreased fertility.