title: Incidence of diffuse FDG uptake in the thyroid of patients with hypothyroidism.
abstract: Positron emission tomography (PET) positive lesions are common in the thyroid. The uptake can be focal or diffuse. Diffuse thyroid uptake is thought to be indicative of autoimmune thyroiditis and not for lesions of malignant potential. Hashimoto's thyroiditis as a cause for diffusely positive thyroid glands has been demonstrated. We determine the incidence of diffuse thyroid PET positivity in hypothyroid patients, presumed to have Hashimoto's thyroiditis. The study design was retrospective database and electronic medical record review. The study setting includes tertiary care and academic health sciences center. The subjects were patients at our medical center who underwent positron emission tomography. Hypothyroid patients were identified who had total body PET imaging performed for any reason. Patients were excluded if they were not taking levothyroxine, had a history of neck surgery, neck irradiation, Graves' disease, taking lithium, thalidomide, amiodarone or interleukin. Patients remaining after the application of these exclusion criteria were presumed to be hypothyroid from Hashimoto's thyroiditis. Only 9.5% of PET scans of hypothyroid patients display diffuse thyroid activity. Only a small minority of presumed Hashimoto's thyroiditis patients will display diffuse thyroid activity after PET imaging. The etiology of this effect is unknown. Diffuse thyroid activity rarely requires surgical intervention.
authors.affiliation: Department of Geriatrics, University of Arkansas for Medical Sciences, 4301 West Markham Street, #806, Little Rock, AR 72205, USA. ivrothman@hotmail.com
authors.forename: Ivey N
authors.initials: IN
authors.lastname: Rothman
authors.forename: Laura
authors.initials: L
authors.lastname: Middleton
authors.forename: Brendan C
authors.initials: BC
authors.lastname: Stack
authors.forename: Twyla
authors.initials: T
authors.lastname: Bartel
authors.forename: Ann T
authors.initials: AT
authors.lastname: Riggs
authors.forename: Donald L
authors.initials: DL
authors.lastname: Bodenner
mesh_terms: D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007037:Hypothyroidism / Q000000981:diagnostic imaging / Q000378:metabolism*; D015994:Incidence; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D011379:Prognosis; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000378:metabolism*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18