title: Evidence for calcitonin-producing cells in human lingual thyroids.
abstract: BACKGROUND
  The thyroid contains two types of cells, the thyroid follicular cells and the calcitonin-producing cells. The site of origin of the thyroid follicular cells is the median thyroid anlage, an endothelial diverticulum in the midline of the ventral pharynx between the first and the second pharyngeal pouches. The ultimobranchial bodies (UBB), a pair of transient embryonic structures evaginated from the fourth pharyngeal pouch and located symmetrically on the sides of the developing neck, are the source of calcitonin-producing cells. In human embryos, the thyroid bud starts its migration at embryonic day 24 and reaches its final location in front of the trachea at embryonic day 45-50. The UBB fuse with the primitive thyroid when thyroid migration is completed. Lingual thyroids result from the failure of the thyroid precursor cells to migrate from the primordial pharynx to the anterior part of the neck. Therefore, calcitonin-producing cells are not expected to be present in lingual thyroids.
  
  
  OBJECTIVE
  Our objective was to determine whether calcitonin-producing C cells are present in ectopic lingual thyroids.
  
  
  METHODS
  We performed calcitonin immunolabeling and transcript detection on four flash-frozen ectopic lingual thyroids. Additional calcitonin immunolabeling was performed on two other paraffin-embedded ectopic lingual thyroids.
  
  
  RESULTS
  We report evidence of calcitonin-producing cells in six independent cases of ectopic lingual thyroids.
  
  
  CONCLUSIONS
  The UBB are not the only source of calcitonin-producing cells in humans. Interactions between calcitonin-producing and thyroid follicular cells occur earlier than previously accepted.
authors.affiliation: Research Center of Sainte-Justine Hospital, Department of Pediatrics, University of Montreal, Montréal, Quebec, Canada H3T 1C5.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Vandernoot
authors.forename: Hervé
authors.initials: H
authors.lastname: Sartelet
authors.forename: Rasha
authors.initials: R
authors.lastname: Abu-Khudir
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Chanoine
authors.forename: Johnny
authors.initials: J
authors.lastname: Deladoëy
mesh_terms: D000293:Adolescent; D000328:Adult; D002116:Calcitonin / Q000235:genetics / Q000378:metabolism*; D002648:Child; D005260:Female; D006801:Humans; D046151:Lingual Thyroid / Q000378:metabolism* / Q000473:pathology; D008297:Male
chemical_list: D002116:Calcitonin