Pre-testicular Azoospermia
Pretesticular azoospermia is characterized by inadequate stimulation of otherwise normal testicles and genital tract. Typically,follicle-stimulating hormone (FSH) levels are low (hypogonadotropic) commensurate with inadequate stimulation of the testes to produce sperm. Examples include hypopituitarism, hyperprolactinemia, and exogenous FSH suppression by testosterone. Chemotherapy may suppress spermatogenesis Pretesticular azoospermia is seen in about 2% of azoospermia.
Post-testicular Azoospermia
In post testicular azoospermia sperm are produced but not ejaculated, a condition that affects 7-51% of azoospermic men. The main cause is a physical obstruction (obstructive azoospermia) of the post testicular genital tracts. The most common reason is a vasectomy done to induce contraceptive sterility.[5] Other obstructions can be congenital (example agenesis of the vas deferens as seen in certain cases of cystic fibrosis) or acquired, such as ejaculatory duct obstruction for instance by infection.