The document discusses male infertility, which accounts for around 30-40% of infertility cases. It provides background information on infertility, noting that around 15% of couples have difficulty conceiving or cannot conceive at all. Diagnosis of male infertility relies on a medical history and semen analysis, which examines the sex cells or sperm. The testes produce both sperm and the hormone testosterone, which controls sperm production and development of male characteristics.