Endocrine Abstracts

Introduction: 2-[18F]FDG PET/CT, commonly used for neoplastic lesions detection, also allows assessment of the severity of the inflammatory processes. Moreover, glucose uptake in spleen and bone marrow may be a useful biomarker of systemic inflammation. Patients with Cushing syndrome demonstrate many metabolic changes involving muscles and fat tissue. Some mechanisms are known, but their relationship to glucose metabolism is not well investigated. Our study aimed to correlate glucose metabolism with the use of 2-[18F]FDG PET/CT in skeletal muscle, adipose tissue, bone marrow and spleen with clinical and metabolic parameters in patients with EAS.

Materials and Methods: Analysis of 2-[18F]FDG PET/CT scans in 13 consecutive patients with EAS in comparison to healthy age, BMI and sex-matched control group was performed. On unenhanced CT scans the body composition on cross-sectional computed tomography images at the L3 level - skeletal muscle area (SMA), skeletal muscle index (SMI), visceral fat area (VFA), visceral fat index (VFI), subcutaneous fat area (SFA), subcutaneous fat index (SFI), intermuscular adipose tissue (IMAT) were assessed. Additionally, cross-sectional area (CSA) and mean attenuation (MA) of each psoas muscle at the L4 level were measured. In 2-[18F]FDG-PET scans, glucose uptake of each psoas (at the L4 vertebra) and femoris muscle (SUV max, SUV peak and SUV mean, target to background ratio [TBR]), as well as glucose uptake of subcutaneous (SAT) and visceral fat (VAT) (SUV max, SUV peak and SUV mean) were analysed. Spleen and bone marrow glucose metabolism (SUV mean, SUV max, spleen to liver ratio [SLR], bone marrow to liver ratio [BLR]) were also evaluated. The results were correlated with clinical and hormonal markers of the disease.

Results: We observed significant positive correlation between presence of metastases and spleen SUV max and SUV mean (P=0.03, P=0.03). Significant negative correlations between morning cortisol level, midnight cortisol level, cortisol after 1 mg of dexamethasone and VAT SUV peak were seen (P=0.049, P=0.029, P=0.017, respectively). Midnight cortisol level was negatively correlated with SAT SUV peak and SUV max (P=0.048, P=0.032, respectively).

Conclusion: Increased spleen FDG uptake, considered to be a surrogate marker of cancer-related inflammation, could be helpful to predict the presence of metastases in EAS. Negative correlation between cortisol levels and glucose metabolism parameters in fat could reflect the dominant role of insulin resistance in adipocytes, abnormal perfusion and vascular function in adipose tissue of EAS patients.