45 – Calcium Homeostasis

Publisher Summary This chapter describes tests focusing on calcium homeostasis. It discusses the assay of nephrogenous cyclic AMP and the protocol involved. After an overnight fast (water may be taken ad libitum), the patient drinks 200 ml of water at 7 A.M. and a further 200 ml at 7.30 A.M. At 8 A.M., the patient empties his bladder and discards the urine. The patient then collects all urine voided during the next 2 hr. During this period, the patient drinks as much water as possible to ensure an adequate urinary volume (some protocols call for 200 ml every 30 min). Blood (15 ml) is taken into an ethylenediaminetetraacetic acid tube in ice at 9 A.M. A final urine specimen is voided at 10 A.M. The 2-h urine volume is noted and an aliquot is kept for cyclic AMP and creatinine assays. The blood is centrifuged as soon as possible after collection and the plasma kept at −20°C until assay. The chapter also presents an overview of the steroid suppression test and parathyroid hormone infusion.