title: The frequency and spectrum of thymus 2-[fluorine-18] fluoro-2-deoxy-D-glucose uptake patterns in hyperthyroidism patients.
abstract: OBJECTIVE
  Thymic hyperplasia is associated with hyperthyroidism. Increased thymus 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) uptake in hyperthyroidism patients has been reported. The aim of this study was to analyze the FDG positron emission tomography (PET) thymus uptake spectrum in patients with active hyperthyroidism with correlation with serum hormones.
  
  
  METHODS
  The prospective study included FDG PET scans from 65 hyperthyroidism patients and 30 subjects with euthyroid status as control group. The intensity of FDG uptake in thyroid and thymus regions was graded subjectively on a five-point scale and semi-quantitatively by measuring standard uptake value (SUV). Correlation coefficient between thymus SUV and serum thyroxine, triiodothyronine, thyrotropin, thyroid peroxidase antibodies (TPO Ab), thyrotropin receptor autoantibody (TR Ab), and thymulin were analyzed.
  
  
  RESULTS
  Among 65 hyperthyroidism patients, 30 (46.2%) and 39 (60%) patients showed thyroid and thymus FDG uptake, respectively. The frequency of thymus uptake FDG was high in patients younger than age 40 (28/31, 90.3%). The patterns of the thymic FDG uptake include inverted V or triangular, separated triangular, united nontriangular, unilateral right or left extension, and focal midline. Focal midline FDG uptake was the most common pattern (15/39, 38.5%). None of the control group showed thymus FDG uptake. The correlation coefficient between the FDG uptake SUV levels in thymus and serum hormones, thyrotropin, TPO Ab, TR Ab, and thymulin levels were all low (P > .05).
  
  
  CONCLUSIONS
  In FDG PET scan, thymus activity was common in hyperthyroidism patients; this should not be misdiagnosed as a malignancy in patients exhibiting weight loss.
authors: Department of Nuclear Medicine and PET Center, Shin Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan.
authors: Yen-Kung
authors: YK
authors: Chen
authors: Chia-Lu
authors: CL
authors: Yeh
authors: Yen-Ling
authors: YL
authors: Chen
authors: Su-Chen
authors: SC
authors: Wang
authors: Ru-Hwa
authors: RH
authors: Cheng
authors: Pan-Fu
authors: PF
authors: Kao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D006980:Hyperthyroidism / Q000000981:diagnostic imaging*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000379:methods*; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D013950:Thymus Gland / Q000000981:diagnostic imaging*; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood
chemical_list: D019275:Radiopharmaceuticals; D013963:Thyroid Hormones; D019788:Fluorodeoxyglucose F18