title: [Osteoporosis in Rheumatoid Arthritis: role of the vitamin D/parathyroid hormone system].
abstract: Osteoporosis is a well-established extra-articular feature of Rheumatoid Arthritis (RA). Systemic inflammation seems to play a crucial role in causing an alteration of multiple homeostatic systems implied in bone health, such as the RANK/RANKL/Osteoprotegerin and Wnt/β catenin pathways; several other causal factors have been called into question, including the chronic use of corticosteroids. Since vitamin D exerts important immune-regulatory roles, it has been claimed that derangement of the vitamin D/parathyroid hormone (PTH) system, a well-known determinant of bone health, may play a pathogenic role in autoimmunity; animal models and clinical data support this hypothesis. Furthermore, RA patients seem to be relatively refractory to vitamin D-induced PTH suppression. Therefore, the link between RA and osteoporosis might in part be due to alterations in the vitamin D/PTH system. A better understanding of the pathophysiology of this system may be crucial to prevent and cure osteoporosis in patients with inflammatory/autoimmune diseases. A major clinical correlate of the strict cooperation and interdependence between vitamin D and PTH is that correction of the vitamin D deficiency, at least in autoimmune diseases, should be targeted to PTH suppression.
authors.affiliation: Unidade de Clínica Médica e Reumatologia, AOU Maggiore della Carità, Novara, Itália. Electronic address: bellanmattia@yahoo.it.
authors.forename: Mattia
authors.initials: M
authors.lastname: Bellan
authors.affiliation: Unidade de Clínica Médica e Reumatologia, AOU Maggiore della Carità, Novara, Itália; Centro de Pesquisa Interdisciplinar de Doenças Autoimunes (Ircad), Departamento de Medicina Translacional, Università del Piemonte Orientale A. Avogadro, Novara, Itália.
authors.forename: Mario
authors.initials: M
authors.lastname: Pirisi
authors.affiliation: Unidade de Clínica Médica e Reumatologia, AOU Maggiore della Carità, Novara, Itália; Centro de Pesquisa Interdisciplinar de Doenças Autoimunes (Ircad), Departamento de Medicina Translacional, Università del Piemonte Orientale A. Avogadro, Novara, Itália.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Sainaghi
mesh_terms: D001172:Arthritis, Rheumatoid / Q000150:complications*; D006801:Humans; D010024:Osteoporosis / Q000209:etiology*; D010281:Parathyroid Hormone / Q000502:physiology*; D014807:Vitamin D / Q000502:physiology*; D014808:Vitamin D Deficiency / Q000150:complications*; D014815:Vitamins / Q000502:physiology*
chemical_list: D010281:Parathyroid Hormone; D014815:Vitamins; D014807:Vitamin D
keywords: Artrite reumatoide; Cholecalciferol; Colecalciferol; Hormônio paratireóideo; Osteoporose; Osteoporosis; Parathyroid hormone; Rheumatoid Arthritis