Inclusion Criteria:  Consecutive NOA patients with a baseline total testosterone level equal to or below 350 ng/dL who had a sperm retrieval procedure by microdissection testicular sperm extraction (micro-TESE) during the study period. Only patients with histopathology-confirmed NOA, absence of Y-chromosome microdeletion in the azoospermia factor 'a' (AZFa) and/or azoospermia factor 'b' (AZFB) region, and with a complete data record for analysis of primary and secondary outcomes were included.  Exclusion Criteria:  Patients subjected to sperm retrieval using percutaneous or non-microsurgical testicular biopsies and those with a history of a previous sperm retrieval attempt. Patients who had used any medication with known potential gonadotoxic effects six months before enrollment and patients under gonadotropin treatment who lost follow-up. Patients with NOA due to hypogonadotropic hypogonadism. Patients who had any number of sperm detected in the ejaculate by routine semen analysis with centrifugation before micro-TESE, including the analysis carried out on the surgery day. The latter relates to the fact that our study is designed to include only patients with NOA confirmed by histopathology, from a specimen obtained during micro-TESE. NOA patients with baseline total testosterone levels above 350 ng/dL.