With primary male hypogonadism, it occurs due to either a congenital or an acquired testicular problem. Congenital means that you are born with it, and acquired means that it is a result of something else, such as trauma, radiation, or mumps.
Secondary male hypogonadism is responsible for most of the low testosterone cases. With this, testosterone levels are low due to complex physiological and behavioral factors that interfere with the production of testosterone. These factors can include obesity, head trauma, and diabetes.