The median age of siblings with hypocalcaemia was 9 years (range 1.3-11 years) and they had significantly lower mean 25OHD (7 vs 15 nmol/L respectively, p<0.001) and a higher mean PTH (175 vs 58 ng/L respectively, p<0.001) and ALP (846 vs 318 IU/L respectively, p<0.001) when compared to the siblings without hypocalcaemia. Here, PTH is linked to Hypocalcemia.