This document discusses the medical causes of infertility in both men and women. It outlines the main causes of female infertility which include defective ovulation, transport, and implantation due to endocrine disorders, physical disorders, ovarian disorders like PCOS, endometriosis, pelvic inflammatory diseases, and uterine fibroids. The main signs for women to see a doctor are irregular periods, painful periods/intercourse, infections, and PCOS symptoms. For men, the main causes are impaired sperm production/delivery and acquired factors like infections, surgeries, illnesses, medications, smoking and lifestyle factors. Both partners should see a doctor if they have been trying to conceive without success for over a year.