Liver Function Tests

Bilirubin needs to be around 60 to see visible jaundice.

AST is less specific than ALT – also produced in kidney, brain etc. But perhaps changes more quickly than ALT. Most important other source of AST and ALT is muscle – so check CK too, especially if bilirubin normal. Myopathies, viral myositis, muscular dystrophy can all present with “abnormal LFTs”.

Gamma GT is also found in other tissues so not 100% specific but typically suggests cholestasis or other biliary problem (together with alkaline phosphatase).

Alkaline phosphatase also produced in bone, so look at calcium, phosphate and vitamin D as well as signs of rickets or renal disease. Most common cause of isolated high alkaline phosphatase is benign transient hyperphosphatasaemia. There is a rare inherited disease of bone/tooth mineralisation, hypophosphatasia, where levels of ALP are abnormally low.

Falling transaminases can be ominous in situation of bilirubin, albumin, coagulation deteriorating…