title: The clinical significance of an isofunctioning thyroid nodule.
abstract: The management of an "isofunctioning" thyroid nodule--defined by radioiodine uptake equivalent to normal thyroid tissue--is often a dilemma. Our goal was to determine the percentage of thyroid nodules that were isofunctioning and the frequency with which carcinoma occurred in an isofunctioning nodule. Patients referred for evaluation of a thyroid nodule from 1990 to 2002 were reviewed and those with an iodine-123 thyroid scintiscan were identified. Nodule size, serum thyrotropin, fine-needle aspiration biopsy, pathology, and follow-up were determined for patients with an isofunctioning, hypofunctioning, or hyperfunctioning thyroid nodule. Of the 562 patients with a thyroid nodule 273 (49%) had a thyroid scan. Nodules were hypofunctioning in 232 (85%), isofunctioning in 29 (11%), and hyperfunctioning in 12 (4%) patients. Mean nodule size and serum thyrotropin level were respectively 2.49 +/- 0.23 cm and 1.73 +/- 0.26 microIU/mL for isofunctioning, 2.47 +/- 0.31 cm and 0.83 +/- 0.21 microIU/mL for hyperfunctioning, and 3.94 +/- 0.13 cm and 1.86 +/- 0.28 pIU/mL for hypofunctioning nodules. Seventeen patients with an isofunctioning nodule underwent thyroidectomy and 12 patients were followed for a mean 27 months without an increase in nodule size. No patient with a hyperfunctioning nodule, six patients (21%) with an isofunctioning nodule, and 44 patients (19%) with a hypofunctioning nodule had a carcinoma. We conclude that the risk of malignancy in an isofunctioning nodule is similar to that of a hypofunctioning nodule and therefore the management should be based on routine fine-needle aspiration biopsy.
authors.affiliation: Department of Surgery, MetroHealth Medical Center, Case Western Reserve University School of Medicine, Cleveland, Ohio 44109-1998, USA.
authors.forename: Nasim
authors.initials: N
authors.lastname: Hedayati
authors.forename: Christopher R
authors.initials: CR
authors.lastname: McHenry
mesh_terms: D000465:Algorithms; D001707:Biopsy, Needle; D006801:Humans; D015995:Prevalence; D013964:Thyroid Neoplasms / Q000097:blood / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology*; D016606:Thyroid Nodule / Q000097:blood / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood
chemical_list: D013972:Thyrotropin