Management of non-obstructive azoospermia.

Non-obstructive azoospermia (NOA) is defined as no sperm in the ejaculate due to failure of spermatogenesis and is the most severe form of male infertility. The etiology of NOA is either intrinsic testicular impairment or inadequate gonadotropin production. Chromosomal or genetic abnormalities should be evaluated because there is a relatively high incidence compared with the normal population. Although rare, NOA due to inadequate gonadotropin production is a condition in which fertility can be improved by medical treatment. In contrast, there is no treatment that can restore spermatogenesis in the majority of NOA patients. Consequently, testicular extraction of sperm under an operating microscope (micro-TESE) has been the first-line treatment for these patients. Other treatment options include varicocelectomy for NOA patients with a palpable varicocele and orchidopexy if undescended testes are diagnosed after adulthood, although management of these patients remains controversial. Advances in retrieving spermatozoa more efficiently by micro-TESE have been made during the past decade. In addition, recent advances in biotechnology have raised the possibility of using germ cells produced from stem cells in the future. This review presents current knowledge about the etiology, diagnosis, and treatment of NOA.