SERPINA1 and congenital bile acid synthesis defect: Usually, an elevated GGT could indicate particularly extrahepatic obstructive lesions (BA) and those involving intrahepatic bile ducts (alpha 1 antitrypsin deficiency, cystic fibrosis, Alagille Syndrome), while a normal or low GGT could indicate BASD or PFIC type 1 or type 2 [30].