Case Author(s): Lisa M. Oakley, M.D. and Barry A. Siegel, M.D. , 12/31/97 . Rating: #D3, #Q3

Diagnosis: Effect of Hyperinsulinemia on FDG Distribution

Brief history:

Elderly man with a remote history of colon cancer.



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View third image(ct). AXIAL CT IMAGE THRU LIVER

Full history/Diagnosis is available below

Diagnosis: Effect of Hyperinsulinemia on FDG Distribution

Full history:

75-year-old man with a history of colon cancer resected seven years ago. CT of the abdomen performed to evaluate newly diagnosed prostate cancer revealed a new hepatic lesion and FDG-PET was requested to evaluate the mass and extent of disease.


F-18 Fluorodeoxyglucose (FDG)


Initial attenuation-corrected PET reprojection images show significant diffuse skeletal muscle and myocardial uptake. The internal organs are difficult to evaluate because of the significant soft tissue uptake and poor visceral organ uptake of FDG. However, an ill-defined focus of increased uptake is seen in the right lobe of the liver. The patient's serum glucose level was within the normal range (80 mg/dL), but on further questioning, the patient revealed that he had eaten breakfast only 2 hours before this study.

A repeat PET study was performed two days later with the patient in a fasting state. The usual distribution of activity is now seen, with improved resolution of the internal organs, decreased skeltal muscle uptake and decreased myocardial uptake. The lesion within the liver is more easily seen and more well defined. No additional abnormal foci of increased uptake are seen.

CT scan through the upper abdomen reveals a 4 x 5 cm. heterogeneous low-density mass within the right lobe of the liver. This mass correlates with the focus of intensely increased FDG uptake seen on PET and is consistent with metastatic disease.


Careful attention to patient preparation is critical for PET imaging. FDG is a glucose analogue that is taken up by glucose membrane transporters on the cell surface of both normal and tumor cells. Uptake of FDG and glucose into malignant cells is facilitated by increased expression of these glucose transporters on the cell surface. If one understands the physiologic basis for FDG distribution in the body, it becomes clear that the patient must be fasting for at least 4-6 hours before injection to assure that serum glucose and insulin levels are at physiologic minimums. Before proceeding with the study, the patient's serum glucose should be checked and one should confirm that the patient has been fasting. The effect of hyperglycemia on FDG uptake is two-fold. First, increased circulating glucose acts as a competitive inhibitor of FDG uptake by direct competition for glucose transporters on the cell surface. This results in a lower cellular concentration of FDG to be imaged by PET and poorer imaging statistics in the organs and tissues of interest (including malignant tumors). Secondly, hyperglycemia stimulates insulin release and circulating insulin preferentially drives glucose and FDG into skeletal muscle. Additionally, myocardial uptake of FDG is greater when blood glucose levels are increased and when hyperinsulinemia secondarily reduces blood free fatty acid concentrations. Less FDG is then available to accumulate in tumor cells.

Thus, despite a normal serum glucose level in this patient prior to FDG injection, significant skeletal muscle and myocardial uptake occured in the first study, presumably as a result of hyperinsulinemia.


Rigo P, Paulus P, Kaschten BJ et al. Oncological applications of positron emission tomography with fluorine-18 fluorodeoxyglucose. Eur J Nucl Med 1996; 23:1641-1674.

Torizuka T, Fisher SJ, and Wahl RL. Insulin-induced hypoglycemia decreases uptake of 2-(F-18)-fluoro-2-deoxy-D-glucose into experimental mammary carcinoma. Radiology 1997; 203:169-172.

Torizuka T. Clavo AC. Wahl RL. Effect of hyperglycemia on in vitro tumor uptake of tritiated FDG, thymidine,L-methionine and L-leucine. J Nucl Med 1997; 38:382-386.


The patient underwent a right hepatectomy, which revealed a moderately differentiated adenocarcinoma consistent with metastasis from the patient's known colon cancer primary.

ACR Codes and Keywords:

References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Gasterointestinal System, Category:Other(Artifact))

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Case number: pt018

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