Vitamin D metabolites: After extraction of serum samples, 25OHD will be measured in a radio-binding assay. The intra-assay and inter-assay variability are 7.5% and 9.6% respectively. The normal range is 9-52 ng/ml. Serum 1,25(OH)2D will be assayed in a radioreceptor assay. The normal adult range is 15-60 pg/ml. The intra-assay and inter-assay variability are 7.6% and 9.8% respectively.