What causes sterile?

I Found this on a another website .

Sterility is classified into two groups, primary and secondary.

• Primary sterility means that a pregnancy has never occurred.
• Secondary fertility involves one or both partners who have conceived previously, but are now unable to do so because of a possible physical or medical condition impairing fertility. A woman who keeps having miscarriages is also considered infertile.

Risk factors for both men and women are the same and these include age, Stress, being underweight or overweight, diet, smoking, alcohol and drugs.

Age plays quite a critical role, as fertility peaks for both men and women in their mid-twenties. Male fertility starts declining in their thirties, while women older than 35 years may experience problems conceiving.

Certain medical conditions such as Diabetes, thyroid disease and anemia may also affect fertility.
Sterility can be caused by many things including medication use and hormone issues. It can also be called by medical conditions such as endometriOSis.
I learned in my health class that the leading cause of sterility is gonorrea.
A large number of factors including Biology, environment, and lifestyle. Some are born sterile, others develop this condition.