Hypercalcaemia induced by excessive parathyroid hormone secretion in a patient with a neuroendocrine tumour

Abstract

1Department of Nephrology, Hopital Conception, Marseille, France and 2Department of Surgery, Hopital Nord, Marseille, France Hyperparathyroidism and neoplasia account for 80–90% of the patients with hypercalcaemia. Serum levels of 1-84 parathyroid hormone (PTH) is the key parameter for the diagnosis and treatment of hypercalcaemia. PTH is elevated in hyperparathyroidism and low in neoplasia [1]. Hypercalcaemia associated with malignancy is most often secondary to a plasma factor, the PTH-related protein (PTHrP), which is responsible for bone resorption. This factor has a PTH-like effect related to its similarity with the PTH N-terminal sequence. However, the biological effects of PTHrP are different from those of PTH as the C-terminal sequences of the two hormones are not the same [2]. PTHrP is not detected by the new technique used for PTH, the immunoradiometric assay (IRMA) [3]. Using this method, both N- and C-terminal sequences of PTH are recognized. PTH level is consistently low in paraneoplastic hypercalcaemia related to PTHrP [4], but exceptionally hypercalcaemia can be due to a nonparathyroid tumour secreting PTH.