title: The sodium-iodide symporter protein is always present at a low expression and confined to the cell membrane in nonfunctioning nonadenomatous nodules of toxic nodular goitre.
abstract: OBJECTIVE
  The sodium-iodide (Na(+)/I(-)) symporter (NIS) is known to be overexpressed in toxic adenomas and in about half of benign solitary nonfunctioning adenomas of the thyroid. In nonfunctioning adenomas, however, the protein is localized mainly in the cytoplasm and fails to reach the basolateral membrane of the follicular cell where it is found in normal thyroid tissue and in hyperfunctioning adenomas. Our aim was to study both the level of expression and the cell localization of NIS in nonfunctioning nonadenomatous nodules of toxic nodular goitre.
  
  
  METHODS
  Tissue specimens from nine patients who were submitted to surgery for toxic or functionally autonomous goitre were studied. Tissues from 12 patients who underwent lobectomy for a toxic thyroid adenoma were used as controls.
  
  
  METHODS
  Tissue sections embedded in paraffin were stained with haematoxylin-eosin for histological evaluation and for immunohistochemistry using a monoclonal antibody that recognized human (h) NIS.
  
  
  RESULTS
  Functioning and nonfunctioning nodules scattered in multinodular goitres consisted of unencapsulated micro/macrofollicular aggregates. All toxic adenomas were characterized by a micro/macrofollicular pattern of growth and histological examination showed that they were surrounded by a capsule. Like the 12 toxic adenomas, all the 14 functioning hyperplastic nodules and two adenomas of toxic multinodular goitre showed a high level of hNIS protein expression with respect to the normal collateral parenchyma and, in all cases, the protein was confined to the cell membrane.
  
  
  CONCLUSIONS
  Contrary to what was observed for solitary nonfunctioning thyroid adenomas, all the 19 nonfunctioning hyperplastic nodules showed a very low hNIS and this was always confined to the cell membrane. These data suggest that the mechanisms leading to loss of iodide uptake in nonfunctioning hyperplastic nodules of toxic multinodular goitre are different from those that act on solitary nonfunctioning follicular adenomas.
authors.affiliation: Dipartimento di Endocrinologia e Metabolismo, Centro Eccellenza Ambisen, Universita di Pisa, Pisa, Italy. mtonacchera@hotmail.com
authors.forename: Massimo
authors.initials: M
authors.lastname: Tonacchera
authors.forename: Paolo
authors.initials: P
authors.lastname: Viacava
authors.forename: Giovanni
authors.initials: G
authors.lastname: Fanelli
authors.forename: Patrizia
authors.initials: P
authors.lastname: Agretti
authors.forename: Giuseppina
authors.initials: G
authors.lastname: De Marco
authors.forename: Melissa
authors.initials: M
authors.lastname: De Servi
authors.forename: Catia
authors.initials: C
authors.lastname: Di Cosmo
authors.forename: Luca
authors.initials: L
authors.lastname: Chiovato
authors.forename: Aldo
authors.initials: A
authors.lastname: Pinchera
authors.forename: Paolo
authors.initials: P
authors.lastname: Vitti
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002462:Cell Membrane / Q000737:chemistry*; D005260:Female; D006044:Goiter, Nodular / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008875:Middle Aged; D027981:Symporters / Q000032:analysis*; D000099209:Sodium-Iodide Symporters
chemical_list: D027981:Symporters; D000099209:Sodium-Iodide Symporters