title: Oral calcium supplementation reverses the biochemical pattern of parathyroid hormone resistance in underprivileged Indian toddlers.
abstract: BACKGROUND
  Toddlers in Pune, India, accustomed to low dietary calcium intake but vitamin D replete have low serum ionised calcium and inappropriately raised serum inorganic phosphorus concentrations together with elevated serum parathyroid hormone (PTH) concentrations. We hypothesised that dietary calcium deficiency leads to end organ resistance to PTH, thus resulting in mild hypocalcaemia and hyperphosphataemia, and that this would be reversed by oral calcium supplementation.
  
  
  METHODS
  51 subjects (25 male; mean (SD) age 2.4 (0.8) years) from an urban slum in Pune were randomised to 500 mg of oral calcium supplement or placebo, daily, for 8 weeks. All subjects received 20 mg of oral elemental iron, daily, as 90% had a serum ferritin concentration <12 microg/l. All subjects were examined for clinical stigmata of rickets and had a wrist radiograph performed. Serum concentrations of ionised calcium, phosphorus, PTH and fibroblast growth factor-23 (FGF-23) were measured at the start and end of the trial.
  
  
  RESULTS
  No subject had clinical or radiological evidence of rickets. There was a significant increase in mean serum ionised calcium concentration (p<0.001) in the supplemented but not the placebo group (p = 0.32). The decrease in mean serum phosphorus concentration in the supplemented group was greater (p<0.001) than in the placebo group (p = 0.003). Mean serum PTH fell in the calcium supplemented (p = 0.001) but not in the placebo (p = 0.303) group. The mean serum FGF-23 concentration did not change in response to calcium supplementation.
  
  
  CONCLUSIONS
  From these data the authors conclude that low dietary calcium intake is associated with resistance to PTH.
authors: Hirabai Cowasji Jehangir Medical Research Institute, Jehangir Hospital, Pune, India.
authors: A
authors: A
authors: Khadilkar
authors: M Z
authors: MZ
authors: Mughal
authors: N
authors: N
authors: Hanumante
authors: M
authors: M
authors: Sayyad
authors: N
authors: N
authors: Sanwalka
authors: S
authors: S
authors: Naik
authors: W D
authors: WD
authors: Fraser
authors: A
authors: A
authors: Joshi
authors: V
authors: V
authors: Khadilkar
mesh_terms: D000886:Anthropometry / Q000379:methods; D002118:Calcium / Q000097:blood / Q000627:therapeutic use*; D002675:Child, Preschool; D004032:Diet / Q000706:statistics & numerical data; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005293:Ferritins / Q000097:blood; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood; D006801:Humans; D007223:Infant; D007227:Infant Nutritional Physiological Phenomena; D007501:Iron / Q000627:therapeutic use; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood* / Q000502:physiology; D010758:Phosphorus / Q000097:blood; D010865:Pilot Projects; D011203:Poverty; D016896:Treatment Outcome
chemical_list: C000717427:FGF23 protein, human; D010281:Parathyroid Hormone; D010758:Phosphorus; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D005293:Ferritins; D007501:Iron; D002118:Calcium