Sperm disorders may result in An inadequate quantity of sperm—too few (oligozoospermia) or none (azoospermia) Defects in sperm quality, such as abnormal motility or structure Etiology of Sperm Disorders Impaired spermatogenesis Spermatogenesis can be impaired (see table Causes of Impaired Spermatogenesis) by the following, resulting in an inadequate quantity or defective quality of sperm: Heat Disorders (endocrine, genetic, genitourinary) Drugs (eg, anabolic steroids) Toxins Table Impaired sperm emission Sperm emission may be impaired because of retrograde ejaculation into the bladder.