Endocrine Abstracts

Objective: We aimed to compare the effectiveness of F-18 fluorodeoxyglucose in positron emission computed tomography (FDG-PET/CT) findings under elevated TSH levels (eTSH) and suppressed TSH levels (sTSH) in differentiated thyroid carcinoma patients with TENIS syndrome (Thyroglobulin-elevated Negative Iodine Scintigraphy).

Methods: A total of 23 patients with differentiated thyroid carcinoma (DTC) who undergone total thyroidectomy and 131I ablation therapy that presenting TENIS Syndrome were included to study. FDG-PET/CT imaging were performed to DTC patients with TENIS syndrome under two hormonal conditions: levothyroxine intake (sTSH) and hormonal withdrawal resulting TSH level ≥ 30 μIU (eTSH). PET/CT imaging findings were compared on the patient and lesion basis for two hormonal conditions.

Results: Positive findings were found in 15 patients with eTSH FDG-PET/CT and in 14 patients with sTSH FDG-PET/CT, and sensitivity was found as 65.2% and 60.8% for both imaging, respectively (P > 0.05). The number of patients who could detect a lesion with eTSH FDG-PET/CT but could not detect any lesion with sTSH FDG-PET/CT was only 1, and there was no change in the clinical management of other 14 patients. Of the total 56 lesions, 47 could be shown eTSH FDG-PET/CT, while 41 lesions could be detected with sTSH FDG-PET/CT (P>0.05). Similarly, mean SUVmax values were also found to be high and not statistically significant in eTSH FDG-PET/CT imaging.

Conclusions: We concluded that eTSH FDG-PET/CT and sTSH FDG-PET/CT imaging have similar results for detecting recurrent disease in DTC patients with TENIS syndrome. On the other hand, it should be considered that eTSH FDG-PET/CT may provide some additional advantages.