I am 35 - no other health issues - no regular medication use.
I have elevated AST's as well - have for 5 years+ Started low
Over the last few years AST's have stayed put around 110ish.
OK FOR MY ADVISE PART:
Not a doctor - but seen a lot of doctors.
5 years later - a few altra sounds - 1 CT - and a recent liver biopsy later(results confirmed TODAY).
I know nothing more today than I did all those years ago - my liver is perfect.
The deal is when you only have elevated AST levels - it's a wait and see game.
You want to at some point elimate liver damage - as the liver can "go" silently.
All other issues associated with elevated AST's would be symptomatic(muscle, blood, heart)
The liver is really the only one of the group that you need to be ahead of the game.
For me - my liver is good - and AST's are still high.
I have two of the best doctor's in my area dealing with this - for now they deal with it and I STOP WORRING!
You seem to be on the right track with the GI - if you ever get to the point where they want to do a biopsy.
I will tell you the worrying far exceeds the discomfort of the actual 2 minute procedure.
Find a good GI - someone you trust and elimate the variables one at a time.
BUT don't waste a lot of time worring - your elevated AST's just might be your "normal".