Hello, an isolated high ggt is can be caused by drugs, alcohol, fatty liver, hepatitis, tumors, etc. The most common causes are drug use (particularly drugs for epilepsy and psychotropic drugs), significant alcohol consumption and fatty liver in diabetes mellitus, alcholol abuse or obesity. More tests are needed to investigate the cause. First of all the other liver enzymes are needed (transaminases and alkaline phosphatase) and then a liver ultrasound scan which can detect anatomic abnormalities (like fatty liver, tumors etc). Mirena can likely cause liver enzyme abnormalities but I would expect more enzymes to be affected (not only ggt that is). I can t exclude it though. More tests are needed. I hope I ve helped! If you d like more information, please let me know. It would be very helpful if I had data like the aforementioned ones. Kind Regards!