High 18F-FDG uptake in PMAH correlated with normal expression of Glut1, HK1, HK2, and HK3

Abstract

Background Primary macronodular adrenal hyperplasia (PMAH) is a rare cause of Cushing's syndrome, characterized by functioning adrenal macronodules and variable cortisol production. Recently, we demonstrated a high 18F-FDG uptake in PMAH, an unexpected finding for a benign disorder. Purpose To investigate whether there is a correlation between 18F-FDG high uptake and the expression levels of the glycolytic pathway components GLUT1, HK1, HK2, and HK3 in PMAH. Material and Methods We selected 12 patients undergoing surgery for PMAH who had preoperatively undergone 18F-FDG PET/CT. mRNA and protein expression of the selected genes were evaluated in the adrenal nodules from patients who underwent surgery through quantitative RT-PCR and by immunohistochemistry, respectively. Results SUVmax in PMAH was in the range of 3.3-8.9 and the adrenal size was in the range of 3.5-15cm. A strong correlation between 18F-FDG uptake and largest adrenal diameter was observed in patients with PMAH. However, no correlation between 18F-FDG uptake and GLUT1, HK1, HK2, HK3 mRNA, and protein expression was observed. Conclusion High 18F-FDG uptake is observed in the majority of PMAH cases. However, 18F-FDG uptake in PMAH is independent of the expression levels of GLUT1, HK1, HK2, and HK3. Further investigation is required to elucidate the molecular mechanisms underlying increased 18F-FDG uptake in PMAH.