Asthenospermia or asthenozoospermia can be defined as the "fatigue" of the spermatozoa which are less mobile than normal. This decreased mobility is most often due to a deformation of the spermatozoa, some of which are unable to move. It can be caused by a disorder in the production of sperm, but other abnormalities such as diabetes can also be the cause. Asthenospermia is responsible for infertility. It is identified by the microscopic study of the sperm in an ejaculation.