Calcitonin immunoreactivity and hypercalcitoninemia in two patients with sporadic, nonfamilial, gastroenteropancreatic neuroendocrine tumors.

BACKGROUND: Hypercalcitoninemia in gastroenteropancreatic tumors associated with calcitonin immunoreactivity is rare.

METHODS: We report here two patients in whom pancreatic neuroendocrine tumors both contained and secreted immunoreactive calcitonin. Both patients experienced elevated basal calcitonin immunoreactivity.

RESULTS: The peak responses of immunoreactive calcitonin occurred 5 minutes after pentagastrin administration in these two patients and were 30% and 180% above basal concentrations corresponding to peak increments of 0.39 and 8.78 ng/ml, respectively. The immunoreactive calcitonin response to pentagastrin in these two patients was not significantly different from that seen among five patients with medullary carcinoma of the thyroid gland.

CONCLUSION: It does not appear that immunoreactive calcitonin responses to pentagastrin stimulation will discriminate between patients with medullary carcinoma of the thyroid gland and those with nonfamilial, gastroenteropancreatic neuroendocrine tumors that express calcitonin immunoreactivity. In patients with secretory diarrhea and/or flushing, an elevated level of immunoreactive calcitonin, in the absence of a thyroid mass in the neck, may herald the presence of a gastroenteropancreatic neuroendocrine tumor.