title: Serum vitamin D levels may not reflect tissue-level vitamin D in sarcoidosis.
abstract: Hypercalcemia in sarcoidosis is due to three mechanistic reasons: (1) systemic conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by the enzyme 1-α hydroxylase produced by activated monocyte/macrophage system, (2) production of parathormone-related peptide (PTHrP) by the sarcoid granuloma, (3) tissue-level conversion of 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D by 1-αhydroxylase produced by local monocyte/macrophage system in the sarcoid granuloma. We report two cases of one proposed mechanism of hypercalcaemia in sarcoidosis (mechanism 3). Both individuals presented with sarcoidosis and 25-hydroxyvitamin D deficiency and developed symptomatic hypercalcaemia with vitamin D replacement. Given their low serum parathormone and parathormone-related peptide levels, low serum 25-hydroxy vitamin D and normal serum 1,25-dihydroxyvitamin D, the systemic 25-hydroxy vitamin D deficiency may not have reflected an increased activity of vitamin D at the local granulomatous tissue level.
authors.affiliation: The Commonwealth Medical College, Scranton, Pennsylvania, USA.
authors.forename: Jill Lauren
authors.initials: JL
authors.lastname: Berlin
authors.forename: Ghanshyam Palamaner Subash
authors.initials: GP
authors.lastname: Shantha
authors.forename: Henry
authors.initials: H
authors.lastname: Yeager
authors.forename: Linda
authors.initials: L
authors.lastname: Thomas-Hemak
mesh_terms: D003937:Diagnosis, Differential; D006099:Granuloma / Q000473:pathology; D006801:Humans; D006934:Hypercalcemia / Q000175:diagnosis / Q000209:etiology*; D008168:Lung / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D012507:Sarcoidosis / Q000150:complications* / Q000378:metabolism / Q000473:pathology; D014807:Vitamin D / Q000032:analysis / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000209:etiology
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D