Non-obstructive azoospermia (NOA) (very little or no sperm cells are produced and none can be found in the ejaculate) can have a number of possible causes. Some of these include hormonal abnormalities, undescended testicles (testicles that have not moved from their initial position in the abdomen to their proper position at birth, in the scrotum), injury to the testicles or genetic causes.
While some of those causes can be treated by hormone therapy or surgery, in certain cases where that is not possible (e.g. ineffective treatment, genetic cause of NOA) or if the couple chooses assisted conception, sperm cells may be retrieved directly from the testes, using surgical sperm retrieval techniques such as TEsticular Sperm Extraction(TESE), followed by IntraCytoplasmic Sperm Injection (ICSI).