Metformin is widely used to treat diabetes, but induces changes in
glucose uptake in both normal organs and
tumors. Here, we review the effects of
metformin on the uptake of 18F-fludeoxyglucose (18F-FDG) in tissues and
tumors, and its influence on
18F-FDG positron emission tomographic imaging (18F-FDG PET), as well as the mechanisms involved. This is an important issue, because
metformin has diverse effects on tissue uptake of
18F-FDG, and this can affect the quality and interpretation of PET images.
Metformin increases
glucose uptake in the gastrointestinal tract, cerebral white matter, and the kidney, while regions of the cerebrum associated with memory show decreased
glucose uptake, and the myocardium shows no change.
Hepatocellular carcinoma and
breast cancer show increased
glucose uptake after
metformin administration, while
thyroid cancer shows decreased uptake, and colon and
pancreatic cancers show no change. A high-energy diet increases
18F-FDG uptake, but this effect is blocked by
metformin. Withdrawal of
metformin 48 h before PET image acquisition is widely recommended. However, based on our review of the literature, we propose that the differentiation of
metformin discontinuation could be reasonable. But future clinical trials are still needed to support our viewpoint.