This is a multicenter, case-control study that aims to investigate the relationship between microbiota and sperm quality via stool, blood, and urine microbiome, metabolomics, and collected clinical metadata. The results of the spermatogenic dysfunction, including aspermia, oligozoospermia, asthenozoospermia, and teratozoospermia, will be compared to normal basic semen analysis utilizing the World Health Organization (WHO) semen analysis procedure 5th edition.

Infertility is a global issue that affects as much as 10%-15% of couples. Approximately half of infertility can be attributed to men. Recently, a worldwide accelerated decline in sperm counts was reported. And the gut microbiome modulates many physiological functions and diseases, including host immunity, metabolic diseases, neuropsychiatric disorders, and so on. Recent publications demonstrate the links between intestinal microbiota and sperm production in fat animals and a few patients. And systemic clinical research would be necessary to explore the human microbiota and males with fertility disorders.

The primary objective of the study is to determine the links between the gut microbiome and sperm quality utilizing microbiome and metabolomics. Stool, blood, and urine will be collected when a patient completes basic semen analysis and informed consent is signed. Microbiome and metabolomics will be compared among aspermia, oligozoospermia, asthenozoospermia, teratozoospermia, and normal individuals.

Inclusion Criteria:

• Aged 18 to 45 years, males
• Body Mass Index (BMI):18.5-29.9 kg/m^2
• After an abstinence period of 2-7 days, two abnormal semen analysis, the absence of spermatozoa from both replicates will be included in the azoospermia group, the total sperm number (<39*10^6 per ejaculate) or the sperm concentration ( < 15 * 10^6 per ml) will be oligozoospermia group, the progressive motility (PR) (< 32%) will be asthenozoospermia group; the percentage of morphologically normal spermatozoa (<4%) will be teratozoospermia group
• Willing to provide feces, urine, blood samples, able to complete study questionnaires aimed at lifestyle factors (cigarette smoking, high temperature environment and others ) and other data collection instruments (e.g. physical activity, food frequency questionnaire, stress and others)

Exclusion Criteria:

• Age < 18 or > 45 years
• History of Zocanidin, Vitamin E, antibiotics, clyster, gastrointestinal endoscope in the past 30 days, or other drugs known to interact with semen quality or gut microbiota, history of high alcohol consumption (liquor over 200 ml, beer over 1000 ml) in the past 7 days or drinking every week in the past month
• A known genetic cause of male factor spermatogenesis dysfunction, including chromosomal or gene disorders (e.g. Y chromosome deletions, CFTR mutation)
• History of male reproductive system (e.g. testis, epididymis, seminiferous duct and others) damage, surgery, tumor or infection
• History of Crohn's disease, ulcerative colitis, acute gastrointestinal disease, renal failure, liver cirrhosis, hypoplasia, X-rays exposure and other diseases related to spermatogenic dysfunction, history of intestinal gastrointestinal surgery (exclude appendix surgery)
• History of psychoses or other mental conditions that would result in cognitive impairment and inability to participate in any part of this study including the informed consent process

Healthy volunteers and patients will be recruited from the outpatient clinics of the Department of Andrology, Reproduction in our participant hospitals. Patients are from licensed doctor of the clinical research center. The age of healthy volunteers and patients in the same hospital will be matched.