RT Journal Article SR Electronic T1 Oral calcium supplementation reverses the biochemical pattern of parathyroid hormone resistance in underprivileged Indian toddlers JF Archives of Disease in Childhood JO Arch Dis Child FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP 932 OP 937 DO 10.1136/adc.2008.149674 VO 94 IS 12 A1 A Khadilkar A1 M Z Mughal A1 N Hanumante A1 M Sayyad A1 N Sanwalka A1 S Naik A1 W D Fraser A1 A Joshi A1 V Khadilkar YR 2009 UL http://adc.bmj.com/content/94/12/932.abstract AB 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 μg/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.