When GGT is two-fold higher than ALP, what is generally assumed to be the source of elevated ALP?

When gamma-glutamyl transferase (GGT) is two-fold higher than alkaline phosphatase (ALP), it typically indicates that the source of the elevated ALP is likely the liver. This is grounded in the relationship between GGT and ALP levels in the context of liver disease versus bone disease.

GGT is an enzyme that is primarily found in the liver, and its levels rise in conditions involving liver dysfunction, biliary obstruction, or liver disease. In contrast, ALP is found in various tissues, including the liver and bones, with specific isoenzymes present for each organ.

When the GGT level is significantly elevated alongside ALP, it suggests a hepatic origin for the alkaline phosphatase increase rather than a skeletal origin. This is because bone-related conditions do not typically result in a markedly elevated GGT. Thus, in scenarios where GGT far exceeds ALP, the liver is inferred to be the source of elevated ALP, reinforcing the understanding of enzyme behavior in pathological states.

In summary, the situation where GGT is substantially higher than ALP suggests that any elevation in alkaline phosphatase is likely associated with liver pathology rather than that of bone or other tissues.