question on high GGT

Hi,

49 yr. old man..weight 212 lbs...feel fine..no outward symptoms....regular exercise.
light drinker...was 2 beers a week..now none. No smoking or drugs.
average health, on no prescriptions...take benadryl daily and zantac 4-5 times a week.
A routine blood test in april showed high GGT 123 and slightly high billirubin. (dont have number)
Same test 6 weeks later showed same results...with GGT 94, still slightly high billirubin. No other liver enzyme tests are abnormal. (no alcohol for 6 weeks leading up to test).

lab work has ruled out:
hepatitis either one
no tumor markers
none of those hereditary diseases
nothing has been found with multiple blood tests.

- cat scan = normal
- ultrasound = small cysts on liver (told dont worry about).
- endoscopy found small gastric ulcer..biopsy normal, treated for a month with meds and I am going back to verify  it's healed w/another endoscopy.
- blood tests results confirmed liver is producing high GGT

3 rd set of blood tests....results slightly high bilirubin..and GGT 160 ( no alcohol now for about 2 months)
- all types of tests in blood lab work....all come back negative.

Doc says I may be one of those people who have high GGT..he is about to give me clean bill of health after 2nd endoscopy and colonoscopy.

Can you think of any other possibilities???

thanks,