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

Abstract

Hyperparathyroidism and neoplasia account for80–90% of the patients with hypercalcaemia. Serumlevels of 1-84 parathyroid hormone (PTH) is the keyparameter for the diagnosis and treatment of hyper-calcaemia.PTHiselevatedinhyperparathyroidismandlow in neoplasia [1]. Hypercalcaemia associated withmalignancy is most often secondary to a plasma factor,the PTH-related protein (PTHrP), which is responsiblefor bone resorption. This factor has a PTH-like effectrelated to its similarity with the PTH N-terminalsequence. However, the biological effects of PTHrPare different from those of PTH as the C-terminalsequences of the two hormones are not the same [2].PTHrP is not detected by the new technique usedfor PTH, the immunoradiometric assay (IRMA) [3].Using this method, both N- and C-terminal sequencesof PTH are recognized. PTH level is consistently lowin paraneoplastic hypercalcaemia related to PTHrP [4],but exceptionally hypercalcaemia can be due to anonparathyroid tumour secreting PTH.We report on a patient with hypercalcaemiarelated to a PTH-secreting neuroendocrine tumour ofthepancreas.Inouropinion,thisisthefirstobservationof a PTH-secreting neuroendocrine tumour of thepancreas.