title: [Hashimoto Thyroiditis and Periodontal Disease: A Narrative Review].
abstract: BACKGROUND
  Currently there is a growing interest in studying systemic conditions with impact on the periodontium. The aim of this article is to determinate if there is a relation between Hashimoto's thyroiditis and periodontal disease.
  
  
  METHODS
  Founded on periodontology based on evidence and in the combination of the keywords: 'Hashimoto disease'; 'Hypothyroidism'; 'Periodontal disease'; 'Systemic Diseases'; a search and evaluation of articles was conducted in Medline, Scopus and Thomson Reuters databases, selecting 30 articles for integral analysis.
  
  
  RESULTS
  There have been developed several studies, searching for a better comprehension about the complexity and pathogenesis of periodontal diseases, associated them to multiple systemic conditions. Actually, the relationship that is best described in the literature is the one with rheumatoid arthritis; however, other relations have been pointed, such as Hashimoto's thyroiditis.
  
  
  CONCLUSIONS
  The identification of multiple etiopathogenic mechanisms common to Hashimoto's thyroiditis and periodontal disease allow to suspect of a relation between them. Some of these mechanisms include the proliferation of lymphocytes T helper 1 and T helper 17 and their impact on the periodontium, the dysfunction of vascular endothelium in gingival microcirculation and the influence of hypothyroidism on bone metabolism, namely on the alveolar bone.
  
  
  CONCLUSIONS
  There is biological plausibility to support the establishment of an association between Hashimoto's thyroiditis and periodontal disease. However, there are not enough studies to support the existence of a causal nexus between these two pathologies, so, in the future, more studies should be conducted to determinate there relation and interaction.
authors.affiliation: Faculdade de Medicina Dentária. Universidade do Porto. Porto. Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Morais
authors.affiliation: Departamento de Periodontologia. Faculdade de Medicina Dentária. Universidade do Porto. Porto. Portugal.
authors.forename: Marta
authors.initials: M
authors.lastname: Resende
authors.affiliation: Departamento de Periodontologia. Faculdade de Medicina Dentária. Universidade do Porto. Porto. Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Pereira
mesh_terms: D050031:Hashimoto Disease / Q000150:complications*; D006801:Humans; D010510:Periodontal Diseases / Q000150:complications*