When an increase in GGT is twofold higher than the increase in ALP, what is assumed to be the source of elevated ALP?

When the increase in gamma-glutamyl transferase (GGT) is significantly higher than the increase in alkaline phosphatase (ALP), it indicates that the elevation of ALP is more likely associated with the liver rather than other sources. GGT is an enzyme that is predominantly found in the liver and plays a role in the transfer of amino acids and the transport of peptides across cell membranes. A twofold increase in GGT suggests liver involvement and indicates that the elevated ALP could also be of hepatic origin.

In contrast, elevated ALP levels are often seen in conditions related to bone disorders, such as Paget's disease or osteomalacia. However, in cases where GGT is more significantly elevated, this typically points away from bone as the source because bone disorders would not usually present with such a pronounced rise in GGT.

Therefore, when interpreting these enzyme levels in conjunction, the situation suggests that the most likely source of the elevated ALP is the liver, especially considering the relationship between the levels of GGT and ALP.