Insulinoma cell calcium-sensing receptor influences insulin secretion in a case with concurrent familial hypocalciuric hypercalcemia and malignant metastatic insulinoma.

[familial hypocalciuric hypercalcemia]

Arterial stimulation and venous sampling (ASVS ) is an important technique for localizing insulinoma . The principle behind ASVS is that insulin secretion is promoted from insulinoma cells by the injection of calcium into the insulinoma -feeding artery . However , the mechanism for ASVS-induced insulin secretion remains unclear . Both insulinoma and familial hypocalciuric hypercalcemia (FHH ) are rare diseases . This study reports on a case in which both of these diseases occur concurrently .The patient with FHH also suffered from insulinoma . We reasoned that insulin secretion for ASVS is dependent on the calcium-sensing receptor (CaSR ). ASVS was performed on this patient . The expression of the CaSR protein and corresponding mRNA were confirmed .No significant changes in the plasma levels of insulin and C-peptide were observed during ASVS . The patient was clinically diagnosed as having FHH . We confirmed that a mutation in the CaSR gene was present in the genomic DNA of this patient and that there were no mutations in the multiple endocrine neoplasia type 1 gene . In addition , expression of both CaSR mRNA and CaSR protein was confirmed in the insulinoma samples .These results suggest that the CaSR gene is involved in ASVS-induced insulin secretion .