Does GGT tell me anything about hepatic fat on liraglutide?

Conditions: GGT · liraglutide.

I want to know whether this is a real physical effect or an artefact of how it is measured.

What prompted the question is an inconsistency between two sources I otherwise trust.

What is the causal chain, and where does it stop being established?

The honest answer is that mild elevation is very common, that it usually improves with weight loss, and that the exceptions are the reason anyone checks.

An isolated result three weeks after starting anything is difficult to interpret. A baseline taken before starting makes the same result trivially interpretable, which is the argument for baselines.

In practice, creatine kinase, alkaline phosphatase and bilirubin together tell you which compartment the abnormality is in, and ordering the transaminases alone throws that information away.

Research-use material of unknown content is an unquantifiable variable in any such attribution.

Transaminases plus bilirubin plus alkaline phosphatase, or you have not measured enough to conclude anything.

Start with the pattern. A hepatocellular pattern with alanine aminotransferase above aspartate aminotransferase points one way; a cholestatic pattern with alkaline phosphatase and gamma-glutamyl transferase points another.

Weight loss of ten per cent or more typically reduces transaminases substantially in people whose elevation was driven by hepatic fat, which is the majority of mild elevations in this population.

Mechanically, alanine aminotransferase is relatively liver-specific; aspartate aminotransferase is also present in muscle, heart and red cells. A raised AST with a normal ALT after heavy resistance training is usually muscle, and creatine kinase settles the question.

Hy's law and its variants are the standard framework for identifying drug-induced liver injury in trials and are why bilirubin is measured alongside transaminases rather than instead.

New training, alcohol and over-the-counter products first. Then the interesting hypotheses.

Before attributing anything to a compound, account for alcohol, muscle injury from new training, and any over-the-counter product being taken alongside.

Gamma-glutamyl transferase is sensitive and unspecific: it rises with alcohol, with several medications and with fatty liver, and an isolated elevation rarely changes anything on its own.

Isolated mild elevation is common and usually improves with weight loss.

Answer first: mild transaminase elevation is common in this population before any drug is involved, and the usual cause is hepatic steatosis rather than anything acute.

Very rapid weight loss can transiently worsen liver biochemistry, which is one of several arguments against pursuing the steepest possible trajectory.

Trials in this class have generally reported improvement rather than deterioration in liver biochemistry, consistent with the weight-mediated mechanism.

Get a baseline before you start anything, because it converts an uninterpretable result into an interpretable one for the cost of one blood draw.