Your liver is composed of mostly liver cells. Basically, these cells provide many different functions unique to the liver. As a result, the liver cells contain specific enzymes and other proteins not found in other cells such as muscle, brain, and nerves. If your liver is exposed to any insult that results in damage to liver cells, the enzymes and proteins within the cells are released into the blood. At this time, it is up to the doctor to determine what insult your liver experienced.
Common causes are hepatitis, alcohol abuse, liver toxins, and others.
Hepatitis B and C are very common in IV drug abusers. You will need to follow up with your doctor. Naltrexone seems to reduce, if not eliminate, the craving for many substances. This is why naltrexone has been approved for nicotine and alcohol abuse. A while back, naltrexone was prescribed to obese patients to see if it decreased the desire to eat.