title: Diffuse thyroid uptake incidentally found on 18F-fluorodeoxyglucose positron emission tomography in subjects without cancer history.
abstract: OBJECTIVE
  We investigated the clinical significance of incidental diffuse thyroid uptake (DTU) on (18)F-FDG PET in subjects without a history of cancer.
  
  
  METHODS
  This study included 2062 studies from adults who underwent (18)F-FDG PET as a cancer screening program. Subjects were divided into the following two groups: with (group I) or without (group II) DTU. The presence of DTU and the thyroid visual grading score were compared with thyroid function tests, serum anti-microsomal antibody (AMA) levels, and the presence of diffuse parenchymal change (DPC) on ultrasonography (USG).
  
  
  RESULTS
  DTU was found in 6.6% of the scans (137/2062). Serum thyroid stimulating hormone (TSH) and AMA levels were significantly higher in group I than in group II. Increased AMA level (55.1%) and DPC (48.7%) were more frequently found in group I (p < 0.001). The proportion of subjects with any abnormal results in serum free thyroxine, triiodothyronine, TSH, or AMA levels or DPC on USG was significantly higher in group I than in group II (71.5% vs. 10.6%, p < 0.001), and was significantly and gradually increased according to the visual grading score group (0 vs. 1-2 vs. 3-4 = 10.6% vs. 58.5% vs. 90.9%, p < 0.001). TSH and is AMA levels were significantly increased according to the visual grading score.
  
  
  CONCLUSIONS
  The presence or degree of incidental DTU on (18)F-FDG PET is closely correlated with increased serum AMA and TSH levels, and the presence of DPC on USG. Therefore, the most plausible pathological cause of DTU may be cell damage by an autoimmune mechanism.
authors.affiliation: Department of Nuclear Medicine, CHA Bundang Medical Center, CHA University, Seongnam 463-712, Korea.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Lee
authors.forename: Joon Young
authors.initials: JY
authors.lastname: Choi
authors.forename: Yoon-Ho
authors.initials: YH
authors.lastname: Choi
authors.forename: Seung Hyup
authors.initials: SH
authors.lastname: Hyun
authors.forename: Seung Hwan
authors.initials: SH
authors.lastname: Moon
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Jang
authors.forename: Yearn Seong
authors.initials: YS
authors.lastname: Choe
authors.forename: Kyung-Han
authors.initials: KH
authors.lastname: Lee
authors.forename: Byung-Tae
authors.initials: BT
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000906:Antibodies / Q000097:blood; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008861:Microsomes / Q000276:immunology; D008875:Middle Aged; D009369:Neoplasms; D049268:Positron-Emission Tomography / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000000981:diagnostic imaging* / Q000378:metabolism; D013972:Thyrotropin / Q000097:blood; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D000906:Antibodies; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D013972:Thyrotropin
keywords: 18F-Fluorodeoxyglucose; Autoimmune thyroid disease; Diffuse thyroid uptake; Positron emission tomography