There are many potential causes of infertility, which can affect either the male, female, or both partners. Common causes include hormonal imbalances, ovulation disorders, sperm abnormalities, tubal blockages, uterine abnormalities, and age-related factors. Infertility can also be caused due to unhealthy lifestyle choices, underlying medical conditions, and environmental factors. 

However, the primary cause of infertility is the inability to conceive despite regular unprotected intercourse. But, other symptoms may be present depending on the underlying cause. In women, irregular menstrual cycles, painful periods, or excessive hair growth may indicate hormonal imbalances or other reproductive issues. In men, changes in sexual function, such as decreased libido or erectile dysfunction, may be signs of infertility.