title: A high prevalence of dual thyroid ectopy in congenital hypothyroidism: evidence for insufficient signaling gradients during embryonic thyroid migration or for the polyclonal nature of the thyroid gland?
abstract: BACKGROUND
  Thyroid ectopy results from the failure of the thyroid precursor cells to migrate from the primordial pharynx to the anterior part of the neck. Most ectopic thyroids are revealed by congenital hypothyroidism and present as a single round mass at the base of the tongue, with no other thyroid tissue. However, some cases have dual ectopy, with part of the tissue having partially migrated. We hypothesized that this occurs more frequently than previously reported.
  
  
  METHODS
  To determine the prevalence of dual ectopy, we reviewed the pertechnetate scintigraphies of 81 patients with congenital hypothyroidism from thyroid ectopy diagnosed between 2002 and 2011 at our institution.
  
  
  RESULTS
  We report a series of seven cases (9%) of dual ectopy, representing an incidence ranging from 1:50,000 to 1:70,000.
  
  
  CONCLUSIONS
  Almost one in 10 cases with congenital hypothyroidism due to thyroid ectopy has dual ectopy. This suggests that two populations of cells diverged at an early stage of development, which may arise from insufficient signaling gradients in surrounding tissues during early organogenesis or may indirectly support the polyclonal nature of the thyroid.
authors.affiliation: Centre Hospitalier Universitaire Sainte-Justine, 3175 Côte Sainte-Catherine, Montréal Québec, Canada.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Wildi-Runge
authors.forename: Sophie
authors.initials: S
authors.lastname: Stoppa-Vaucher
authors.forename: Raymond
authors.initials: R
authors.lastname: Lambert
authors.forename: Sophie
authors.initials: S
authors.lastname: Turpin
authors.forename: Guy
authors.initials: G
authors.lastname: Van Vliet
authors.forename: Johnny
authors.initials: J
authors.lastname: Deladoëy
mesh_terms: D002465:Cell Movement / Q000502:physiology; D003409:Congenital Hypothyroidism / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000473:pathology; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D008297:Male; D009055:Mouth / Q000473:pathology; D015995:Prevalence; D011877:Radionuclide Imaging; D015398:Signal Transduction / Q000502:physiology*; D013234:Stem Cells / Q000378:metabolism / Q000473:pathology; D050033:Thyroid Dysgenesis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000473:pathology; D013961:Thyroid Gland / Q000002:abnormalities* / Q000378:metabolism