Hello - thanks for asking your question.
First off, I would repeat the liver tests to make sure they are accurate. Assuming they are, there are several considerations that can raise the liver tests this high. They include alcoholic hepatitis, viral hepatitis, toxic hepatitis (i.e. with Tylenol - although the AST and ALT would typically be in the thousands), ischemic hepatitis (again, the AST and ALT would typically be in the thousands), Wilson's disease (a genetic liver disease that can present with acute hepatitis), and autoimmune hepatitis.
Seeing a specialist is a good idea. Tests include a viral hepatitis screen, autoimmune hepatitis screen, tests for Wilson's disease (i.e. serum ceruloplasmin level) should all be considered. I would also perform an abdominal ultrasound to image the liver. If these tests are non-revealing, your specialist may consider a liver biopsy.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.
Here's some info you might want to look at
http://www.sydpath.stvincents.com.au/tests/GGT.htm
http://www.labcorp.com/datasets/labcorp/html/chapter/mono/pr004400.htm
Thanks,
Tom