; Liver labs can be difficult to interpret as there are many different causes for elevations. LFT's are also rather fluid and dynamic and can change quite a bit over relatively short periods of time. GGT in particular can jump around a lot, and even moderate amounts of alcohol can spike GGT. 383 IS impressive though.
Many medications can elevate LFT's too. You mention his cholesterol/triglyceride levels are high... Is he on statins to control these? Is he taking over the counter or prescription pain meds for any chronic condition?
What's most often misunderstood about LFT's is that they are not a very good indicator of cumulative damage to the liver, but rather a good indicator of just how angry or inflamed the liver was in the days leading up to the blood draw. Many liver patients with substantial/permanent damage have liver enzymes that return to normal once their hepatitis, alcohol or whatever have been resolved. Likewise, those with acute liver disease (hepatitis A) can spike sky-high enzymes for several months, but recover with little or no permanent damage.
Most doctors don't get too excited about mildly elevated LFT's until levels reach double the normal upper limits over a period of several tests done over several months time. As 2 of your son's enzymes are double or more normal, this is a rationale/justification to monitor these enzymes more closely than the usual annual checkup. 90 days is the usual period for a re-check in situations like this, and if his doctor hasn't requested he come back to follow up in this your son should request this.
In the mean time, you might want to look into "possible suspects" for what might be causing this problem. Medications, alcohol, a high carb diet (especially fructose), elevated weight (fatty liver is epidemic), toxic exposures at work, and many other things might be to blame.
Moderately elevated LFT's like this shouldn't be cause for major alarm, but aren't the kind of thing you want to ignore either. You've got to work on the cause until you find it, and keep going back for labs to be certain nothing is getting worse and you've got things headed in the right direction.
Best of Luck to you both!