title: Activating antibodies to the calcium-sensing receptor in two patients with autoimmune hypoparathyroidism.
abstract: Autoimmune hypoparathyroidism is thought to result from immune-mediated destruction of the parathyroid glands. We encountered two patients with hypoparathyroidism and other autoimmune conditions (Graves' disease and Addison's disease, respectively) in whom autoimmune destruction of the parathyroid glands had not taken place. In the first, a histologically normal parathyroid gland was observed at the time of subtotal thyroidectomy; and in the second, the hypoparathyroidism remitted spontaneously. Both patients had antibodies that reacted with the cell surface of bovine parathyroid cells and human embryonic kidney (HEK293) cells transfected with the extracellular calcium-sensing receptor (CaR) but not with nontransfected HEK293 cells. The antibodies also reacted with the same bands on Western analysis of extracts of bovine parathyroid tissue and CaR-transfected HEK293 cells that were identified by an authentic, polyclonal, anti-CaR antiserum and reacted with several peptides with sequences from the CaR's extracellular domain. These anti-CaR antibodies activated the receptor based on their ability to increase inositol phosphate accumulation, activate MAPK, and inhibit PTH secretion. These results, therefore, demonstrate that patients with the biochemical findings of primary hypoparathyroidism can harbor activating antibodies to the CaR, which, in the two cases studied here, did not produce irreversible destruction of the parathyroid glands.
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Kifor
authors.forename: Aidan
authors.initials: A
authors.lastname: McElduff
authors.forename: Meryl S
authors.initials: MS
authors.lastname: LeBoff
authors.forename: Francis D
authors.initials: FD
authors.lastname: Moore
authors.forename: Robert
authors.initials: R
authors.lastname: Butters
authors.forename: Ping
authors.initials: P
authors.lastname: Gao
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Cantor
authors.forename: Imre
authors.initials: I
authors.lastname: Kifor
authors.forename: Edward M
authors.initials: EM
authors.lastname: Brown
mesh_terms: D000224:Addison Disease / Q000150:complications; D000328:Adult; D000818:Animals; D001323:Autoantibodies / Q000032:analysis* / Q000276:immunology*; D001327:Autoimmune Diseases / Q000097:blood / Q000150:complications / Q000276:immunology*; D015153:Blotting, Western; D002417:Cattle; D002460:Cell Line; D006111:Graves Disease / Q000150:complications; D006801:Humans; D007011:Hypoparathyroidism / Q000097:blood / Q000150:complications / Q000276:immunology*; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010281:Parathyroid Hormone / Q000037:antagonists & inhibitors; D010446:Peptide Fragments / Q000276:immunology; D011233:Precipitin Tests; D044169:Receptors, Calcium-Sensing / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism; D014162:Transfection
chemical_list: D001323:Autoantibodies; D007295:Inositol Phosphates; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D044169:Receptors, Calcium-Sensing; D020928:Mitogen-Activated Protein Kinases