Alopecia is the medical term for baldness. 
Alopecia occurs naturally in many men as they grow older.
A tendency to go bald is inherited and usually begins at the temples or the crown of the head.
In rare cases, baldness is due to an abnormal reaction to the hair substance itself.
This could result in a total loss of hair.
Alopecia is also a temporary side effect of many cancer chemotherapy drugs.