title: Bioavailable vitamin D levels are reduced and correlate with bone mineral density and markers of mineral metabolism in adults with nephrotic syndrome.
abstract: OBJECTIVE
  Blood levels of 25-hydroxyvitamin D [25(OH) D] are reduced in patients with nephrotic syndrome (NS). The lowering is thought to be due to urinary loss of vitamin D binding protein (DBP). A link between vitamin D deficiency and bone disease or markers of mineral metabolism has not yet been shown in NS. We hypothesized that alterations in bioavailable vitamin D levels might be linked to these abnormalities in NS.
  
  
  METHODS
  We measured circulating levels of 25(OH)D, 1,25-dihydroxyvitamin D [1,25(OH)2 D], DBP, serum albumin and intact parathyroid hormone (iPTH) in 106 adults with sporadic idiopathic NS and 40 healthy controls. Bioavailable vitamin D was calculated from previously validated formulae. Bone mineral density (BMD) was measured at left hip (neck of femur) by DEXA.
  
  
  RESULTS
  Compared to healthy controls, total and bioavailable 25(OH)D levels were significantly reduced in patients with NS as compared to healthy controls. Among the nephrotic patients, BMD was positively correlated with bioavailable 25(OH)D (r = 0.358; P = 0.0002) but not with total 25(OH)D (r = 0.174; P = 0.079). Total 1,25(OH)2 D and bioavailable 1,25(OH)2 D did not correlate with BMD (r = 0.131; P =  0.206 and r = 0.107, P = 0.295). Bioavailable 25(OH)D levels showed a strong inverse correlation with iPTH on univariate (r = -0.457; P < 0.0001) and multivariate (β=-0.453, P < 0.0001) analyses.
  
  
  CONCLUSIONS
  We conclude that bioavailable 25(OH)D is a better measure of vitamin D status with respect of BMD and mineral metabolism in patients of nephrotic syndrome.
authors.affiliation: Departments of Internal Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Aggarwal
authors.affiliation: Departments of Nephrology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Yadav
authors.affiliation: Departments of Nephrology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Raja
authors.initials: R
authors.lastname: Ramachandran
authors.affiliation: Departments of Nephrology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
authors.affiliation: Departments of Nephrology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Vivek
authors.initials: V
authors.lastname: Kumar
authors.affiliation: Departments of Endocrinology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Naresh
authors.initials: N
authors.lastname: Sachdeva
authors.affiliation: Departments of Radiodiagnosis, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
authors.forename: Niranjan
authors.initials: N
authors.lastname: Khandelwal
authors.affiliation: Departments of Nephrology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.|George Institute for Global Health, New Delhi, India.|University of Oxford, Oxford, UK.
authors.forename: Vivekanand
authors.initials: V
authors.lastname: Jha
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015519:Bone Density; D016723:Bone Remodeling; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D015536:Down-Regulation; D005260:Female; D005272:Femur Neck / Q000378:metabolism* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009404:Nephrotic Syndrome / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology; D010281:Parathyroid Hormone / Q000097:blood; D011237:Predictive Value of Tests; D012709:Serum Albumin / Q000032:analysis; D000075462:Serum Albumin, Human; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood* / Q000175:diagnosis / Q000503:physiopathology; D014809:Vitamin D-Binding Protein / Q000097:blood; D055815:Young Adult
chemical_list: C422455:ALB protein, human; D015415:Biomarkers; C470125:PTH protein, human; D010281:Parathyroid Hormone; D012709:Serum Albumin; D014809:Vitamin D-Binding Protein; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D000075462:Serum Albumin, Human
keywords: bioavailable; bone mineral density; nephrotic syndrome; parathyroid hormone; vitamin D