Dear Chan,
The GGT is a very sensitive test. Elevation of GGT levels are not indicative for any specific illness. In general terms, when the GGY is elevated the first step is to rule out structural abnormalities of the liver and obstruction of the bile ducts by gallstones. This is accomplished by doing an ultrasound of the liver or a CT scan.
Once structural causes are excluded, attention is focused on excluding conditions that injure the liver cells. Usually, other liver tests are also increased (e.g. SGOT, SGPT also known as AST and ALT)when liver cellsa re injured or leaky.
The possible causes for liver injury are multiple and include viral infection, alcohol-induced liver damage, autoimmune disease, medication or occupational related injury and metabolic abnormalities. Fatty liver, a condition in whcih fat is deposited in liver cells, is a frequent cause for an elevated GGT.
The only way to be certain of the specific etiology is to have the appropriate blood tests to exclude the other causes. If liver tests improve with weight loss that would be indirect evidence to suggest fatty liver. Often, however, a liver biopsy is required for a definitive diagnosis.
This information is presented for educational purposes. Ask specific questions to your personal physician.