Introduction: Vasoactive intestinal peptide-producing tumours (VIPomas) represent a rare type of neuroendocrine tumour whose incidence is 1 in 10 million per year. Most are located in the pancreas. They cause diffuse watery (secretory) diarrhoea, hypokalaemia and achlorhydria and also appear as an uncommon cause of hypercalcaemia.
Case report A 69-year-old female with previous diagnosis of a non-functioning neuroendocrine pancreatic tumour (2005) with liver metastasis (2009) was admitted for weakness and severe hypokalaemia. She had been admitted for hypercalcaemia a few months before. Her family history was a priori negative for MEN-1 affected. She complained of chronic watery diarrhoea that persisted with fasting (610 stools/day) in spite of multiple therapies (surgery, long acting somatostatin analogues, systemic chemotherapy and transarterial hepatic chemoembolization). Analysis showed: impaired fasting glucose (159 mg/dl), hypokalaemia (2.6 mEq/l), metabolic acidosis (pH 7.34, serum bicarbonate 15.1 mmol/l), hypophosphatemia (1 mg/dl), hypomagnesemia (1.6 mg/dl) and hypercalcaemia (until 15.3 mg/dl). Serum TSH, calcitonin, cortisol, PRL, glucagon, PTH-rp and 5HIAA were normal. PTH 23.8 pg/ml. 25-0H-vitamin D 35.6 nmol/l. CgA 115 ng/ml. VIP concentrations were high (>116 pmol/l, normal <30 pmol/l). Gastrin 149 pg/ml (13115). An octreoscan showed known liver disease. There were no bone metastases. Immunohistochemistry was positive for somatostatin, synaptophysin and chromogranin A. Patient needed to be managed with high doses of supplements of potassium, magnesium, phosphorus, periodic i.v. bisphosphonates and a high salt intake. Recently, an essay of cinacalcet was added because of persistent hypercalcaemia.
Discussion: A clinical redefinition of diagnosis was made: VIPoma. Hypercalcaemia might be explained by the stimulatory effect of VIP on bone resorption. However, if normal feedback is intact, PTH concentrations should be low, whereas the patient described had a normal PTH. We have observed a sustained response of calcium levels since cinacalcet introduction. 5% of VIPomas are in context of MEN-1.