ABSTRACT
Background & objectives: Estimation of parathyroid hormone (PTH) levels is important in the management of metabolic bone disorders. Here we describe a simple, sensitive and specific second generation immunoradiometric assay (IRMA) to detect intact PTH levels using different solid phase matrices. Different methods for immobilization of antibodies have also been evaluated. Methods: Experiments were carried out with physical adsorption of antibodies, covalent coupling using 2 per cent glutaraldehyde and N,N`carbonyldiimidazole. In all cases, antibodies raised against C-terminal were used as solid phase agent. Detector antibodies were N terminal antibodies that were radio-iodinated with 125I followed by gel purification. Several of the antibodies coupled to various solid phase matrices were incubated with PTH standards and the detector antibody as well as the commercially available tracer from DiaSorin kit to identify a suitable match pair. Results: The best pair was polyclonal C-terminal PTH antibody along with the kit tracer from DiaSorin with regards to antibody coated to magnetic cellulose particles. Among the various antibodies and the solid phases evaluated, the best assay was obtained with the matched pair of antibodies (70×G67 and 70×G68) from Fitzgerald immobilized on polystyrene tubes. The polyclonal antibody against C-terminal PTH was chosen as the capture antibody and 125I labelled polyclonal antibody against N-terminal PTH as the tracer. The sample values obtained in the antibody coated tubes were comparable to those obtained using a commercial kit. Interpretation & conclusions: The results indicated the feasibility of adopting this system for further development into a PTH IRMA for regular production as there is no indigenous kit available for intact PTH.
ABSTRACT
BACKGROUND & OBJECTIVE: Data on the vitamin D status of the population in a tropical country like India have seldom been documented. Vitamin D deficiency is presumed to be rare. We carried out this study to document the dietary habits, serum calcium, 25(OH)vitamin D [25(OH)D], and parathyroid hormone levels of urban and rural population in a State in south India. METHODS: A total of 943 healthy urban and 205 rural adult subjects and 76 urban and 70 rural healthy children were studied for their dietary pattern, serum calcium, phosphorus, alkaline phosphatase, 25(OH)D, and N-tact parathyroid hormone levels (N-tact PTH). RESULTS: The daily dietary calcium intake of both the urban and rural population was low compared to that of recommended daily/dietary allowances (RDA) issued by Indian Council of Medical Research (ICMR). Dietary calcium and phosphorus were significantly lower(P<0.0001) in both the rural adult and children compared to that of the urban adult and children. The dietary phytate to calcium ratio was significantly (P<0.0001) higher in rural adult and children compared to that of urban adult and children. N-tact PTH levels negatively correlated with 25(OH)D in rural (r=-0.24; P<0.002), in urban adult subjects (r=-0.12; P<0.0001) and in rural and urban children (r=-0.2; P<0.05). The 25(OH)D levels of rural adult subjects were significantly higher (P<0.001) than that of urban adult subjects in both males and female groups. The 25(OH)D levels of both the urban and rural children were low. INTERPRETATION & CONCLUSION: Low dietary calcium intake and 25(OH)D levels were associated with deleterious effect on bone mineral homeostasis. Prospective longitudinal studies are required to assess the effect on bone mineral density, a surrogate marker for fracture risk and fracture rates.