There is no doubt about it, in the world of anabolic androgenic steroids testosterone is king and in the human body itself it is an imperative hormone. Yes, there are side effects of testosterone use but they are manageable, largely preventable and often of no concern if were responsible. There is a very real risk to reward ratio that exist around exogenous testosterone use; the more we use the greater the reward but the more we use the greater the potential for negative or adverse side effects. Further and often overlooked, a healthy diet can greatly improve our odds; as cholesterol and blood pressure can be a concern we should consume diets that promote healthy levels of both.
iNOS is known for releasing large amounts of nitric oxide as a defensive tactic. Nitric oxide is a free radical that can be used as a weapon and, therefore, sudden low testosterone essentially puts a huge oxidative load on the brain and may actually do some damage that leads to Parkinson's.  A further verification of this is the fact that, according to one study, men are times more likely to contract Parkinson's and that low testosterone levels have been associated with Parkinson's.  In addition, giving male Parkinson's patients testosterone can help with tremors. 
Research shows little evidence of abnormal or unhealthy psychological changes in men receiving supervised testosterone therapy to treat their low T, according to a study in the journal Therapeutics and Clinical Risk Management. However, mental and physical risks are involved in self-administration of artificial testosterone. Anyone abusing synthetic testosterone, also known as anabolic steroids, may experience episodes of aggressive or violent behavior, along with physical side effects. Bodybuilders, athletes, or anyone who seeks to build muscle mass or achieve other benefits from artificial testosterone should be aware of these risks.