title: Pituitary 18F-FDG Uptake Correlates With Serum TSH Levels in Subjects With Diffuse Thyroid 18F-FDG Uptake.
abstract: OBJECTIVE
  This study was to evaluate the relationship among FDG uptake in the pituitary gland (FDGp), FDG uptake in the thyroid gland (FDGt), and serum thyroid-stimulating hormone (TSH) levels in patients with diffuse FDGt incidentally noted on positron emission tomography/computed tomography (PET/CT).
  
  
  METHODS
  We retrospectively reviewed FDG PET/CT scans of 2,945 subjects who underwent health screening. Of these, 44 subjects had diffuse FDGt and available thyroid function tests. FDGt and FDGp were correlated with serum TSH. FDGp in 44 paired control subjects without FDGt and 15 thyroid cancer patients undergoing thyroid hormone withdrawal were additionally measured, and compared with FDGp in the 44 subjects with FDGt divided into 3 groups according to serum TSH levels.
  
  
  RESULTS
  In the 44 subjects, there was a strong correlation found between FDGp and TSH (P < 0.001, r = 0.618). As well, there were statistically significant differences in FDGp between the low, normal, and high TSH groups (P < 0.001). FDGp in the paired control subjects was not different from that in the normal TSH group (P = 0.384), and FDGp in the TSH-stimulated thyroid cancer patients was not different from that in the high TSH group (P = 0.463).
  
  
  CONCLUSIONS
  We found a strong positive correlation between pituitary FDG uptake and serum TSH. Pituitary FDG uptake seems to hold an important clue to the functional status of the thyroid in subjects with diffuse thyroid FDG uptake. Furthermore, physiologic FDG uptake in the pituitary gland caused by hypothyroidism should not be confused with pathologic conditions such as macroadenoma or metastases.
authors.affiliation: From the *Department of Nuclear Medicine, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea; †Yonsei University College of Medicine, Seoul, Korea; ‡Department of Internal Medicine, Severance Hospital, Endocrine Research Institute, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea; §Department of Surgery, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea; and ∥Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Yong Hyu
authors.initials: YH
authors.lastname: Jeong
authors.forename: Dongwoo
authors.initials: D
authors.lastname: Kim
authors.forename: Jeong Won
authors.initials: JW
authors.lastname: Lee
authors.forename: Yumie
authors.initials: Y
authors.lastname: Rhee
authors.forename: Kee-Hyun
authors.initials: KH
authors.lastname: Nam
authors.forename: Mijin
authors.initials: M
authors.lastname: Yun
authors.forename: Chun Ki
authors.initials: CK
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D010902:Pituitary Gland / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D013961:Thyroid Gland / Q000000981:diagnostic imaging*; D013972:Thyrotropin / Q000097:blood*; D014057:Tomography, X-Ray Computed
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013972:Thyrotropin