Changes of FDG brain uptake in patients with abnormal thyroid function

  • Dr Wen-Sheng Huang, Department of Nuclear Medicine, Tri-Service General Hospital, Taipei, Taiwan
  • Dr Chih-Yung Chang, Department of Nuclear Medicine, Tri-Service General Hospital, Taipei, Taiwan
  • Dr Cheng Yi Cheng, Department of Nuclear Medicine, Tri-Service General Hospital, Taipei, Taiwan

    • Objective: To investigate FDG brain uptake in patients with hypo- and subclinical hyperthyroidism undergoing whole-body FDG PET/CT.

    Methods: Sixty-four patients who had received total thyroidectomy for thyroid carcinoma underwent whole-body FDG PET/CT. Thirty-two of them received imaging in subclinical hyperthyroid status (15 males; 17 females; mean age, 55 ± 14 years) while the other 32 age-matched patients underwent the scan 4 wk after thyroid hormone withdrawal (12 males; 20 females; mean age, 56 ± 13 years). Brain images were performed 1 h after 370 MBq intravenous injection using a dedicated PET/CT (Siemens Biograph BGO duo). FDG-uptake was quantified by the standardized uptake value (SUV), normalized to patient’s body weight. The volume of brain was determined by PET with 40% maximum SUV threshold. The brain mean SUV (SUVmean) were calculated in each patient. Data were compared between the two groups.

    Results: The brain mean SUVs for the hypothyroid patients ranged between 3.11 and 6.35 (averaged SUVmean 5.13 ± 0.91) while those of the subclinical hyperthyroid patients varied from 3.53 to 8.29 (mean SUVmean 5.77 ± 1.04). There was a significant global reduction of brain FDG uptake in the hypothyroid group (11.1%, P < 0.01) but no significant changes in the sub-clinical hyperthyroid group compared to the controls.

    Conclusion: FDG brain uptake in subclinical hyperthyroid patients was significantly greater than that of patients with hypothyroidism, suggesting effects of thyroid hormone on cerebral glucose metabolism.