title: Relation between circulating levels of 25(OH) vitamin D and parathyroid hormone in chronic kidney disease: quest for a threshold.
abstract: BACKGROUND
  Vitamin D deficiency is common in patients with chronic kidney disease (CKD). Current guidelines recommend treatment strategies in these patients similar to those for the general population, but the vitamin D nutritional status sufficient to prevent PTH levels from increasing in CKD is unknown. OBJECTIVE, MAIN OUTCOME MEASURE: Our aim was to study the relation between circulating PTH and 25(OH)D levels and to search for a 25(OH)D threshold associated with a significant PTH increase.
  
  
  METHODS
  In the hospital-referred NephroTest cohort study, we measured 25(OH)D, PTH, and glomerular filtration rate (mGFR) by ⁵¹Cr-EDTA renal clearance in 929 adult patients with nondialysis CKD stages 1 to 5 and no vitamin D supplementation. Patients' mean age was 60.1 ± 14.7 years; 71% were men, and 9% were black. Their median mGFR was 37.8 mL/min/1.73 m².
  
  
  RESULTS
  We found a 25(OH)D threshold of 8 ng/mL with an upper limit of 20 ng/mL (95% confidence interval) by linear piecewise regression modeling of log-PTH for 25(OH)D adjusted for mGFR, age, race, and ionized calcium level. The smoothed curve confirmed that PTH concentration rose steeply when circulating 25(OH)D levels fell to less than 20 ng/mL.
  
  
  CONCLUSIONS
  Spontaneous 25(OH)D levels greater than 20 ng/mL seem sufficient to control serum PTH in CKD patients. This result reinforces guidelines to supplement vitamin D only if less than 30 ng/mL.
authors: Institut National de la Santé et de la Recherche Médicale, Centre for Research in Epidemiology and Population Health, CESP, U1018, Diabetes, Obesity, and Chronic Kidney Disease Epidemiology Team, 94807 Villejuif, France. marie.metzger@inserm.fr
authors: Marie
authors: M
authors: Metzger
authors: Pascal
authors: P
authors: Houillier
authors: Cédric
authors: C
authors: Gauci
authors: Jean Philippe
authors: JP
authors: Haymann
authors: Martin
authors: M
authors: Flamant
authors: Eric
authors: E
authors: Thervet
authors: Jean-Jacques
authors: JJ
authors: Boffa
authors: François
authors: F
authors: Vrtovsnik
authors: Marc
authors: M
authors: Froissart
authors: Bénédicte
authors: B
authors: Stengel
authors: Pablo
authors: P
authors: Ureña-Torres
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000368:Aged; D002112:Calcifediol / Q000097:blood*; D002118:Calcium / Q000097:blood / Q000652:urine; D015331:Cohort Studies; D005260:Female; D005602:France / Q000453:epidemiology; D005919:Glomerular Filtration Rate; D006801:Humans; D006934:Hypercalcemia / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010710:Phosphates / Q000097:blood / Q000652:urine; D017410:Practice Guidelines as Topic; D015995:Prevalence; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000503:physiopathology / Q000652:urine; D012720:Severity of Illness Index; D014808:Vitamin D Deficiency / Q000175:diagnosis* / Q000209:etiology
chemical_list: C470125:PTH protein, human; D010281:Parathyroid Hormone; D010710:Phosphates; D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol; D002118:Calcium