Parathyroid hormone and secondary renal hyperparathyroidism

Parathyroid hormone (PTH) increases the renal re-absorption of calcium, reduces that of phosphorus, stimulates renal synthesis of active vitamin D, causes a mobilisation of bone calcium and inhibits the production and activity of erythropoitin. A secondary hyperparathyroidism may result from metabolic disturbances with stage III and IV chronic renal insufficiency (CRF). Reduction in the production of vitamin D increases the feedback control on (PTH). The hyperparathyroidism is firstly compensated by-induction of synthesis of calcitriol. However the biosynthesis of calcitriol is not maintained in CRF and the parathyroid glands become insensitive to feedback control. Consequences are bone demineralisation, ectopic calcification of soft tissue and anaemia. Treatment is by dietary management.