This is a very serious situation as hormones can be very dangerous when used inappropriately like in the case of your daughter’s boyfriend.
Testosterone therapy to aid in muscle building is known to cause a variety of dangerous health issues. In addition, they are associated with an unstable mental state characterized by increased tendencies to depression and aggressiveness. The increase in aggressive behavior often seen with testosterone use can be very dangerous to the individual and to those around them. Fits of rage and violence are not uncommon for people using testosterone for the purpose of enhancing muscle building. When coming off of anabolic steroids depression is a common side effect due to the sharp decline in circulating testosterone levels.
From a physical standpoint, anabolic steroids like testosterone are known to enhance tumor growth and are associated with a specific type of dangerous liver tumor that can be fatal if rupture occurs. These tumors are highly vascularized (lots of blood vessels) and are predominantly asymptomatic. This means that most of the time a person never knows they have one until it ruptures which is a very serious life threatening situation. Long term use is also associated with damage to the heart and cardiovascular system and can cause fatal heart attacks and strokes.
Pimples, hair loss, low libido, decreased sperm count, impotence, breast formation, and shrinkage of the testes are all additional side effects he can expect to experience from taking average doses of anabolic steroids. One of the most significant dangers of steroid use (even when used at prescribed doses) is that the negative effects may not become evident until years after they are used.
He is at additional risk due to the fact he is injecting the drug. This raises his chances of contracting blood borne diseases such as HIV and Hepatitis B and C.
If he is a teenager he can expect his growth to be stunted for the rest of his life.
This is a very serious situation and hopefully with the right information, guidance and help he will make the right decision about his body and health.