Hypercalcitoninemia in a patient with a recurrent goitre and insulinoma: a case report

Serum calcitonin has become a very sensitive and specific marker for medullary thyroid carcinoma that should be determined in patients with nodular thyroid disease. However, a few earlier reports indicated that tumors other than medullary thyroid carcinoma including insulinomas arising from pancreatic islet cells may also produce calcitonin. Of the few cases of calcitonin-producing insulinomas previously reported, most had incomplete data or lack of documentation of the association between raised serum calcitonin concentration and immunohistochemical detection of calcitonin in pancreatic islet cell tumors. In this paper we are reporting a 54-year-old woman with a history of partial thyroidectomy for multinodular goitre at the age of 50 yrs, she was evaluated for a 2-months history of fasting hypoglycemia (plasma glucose 1.9 mmol/L during a supervised fast), raised serum insulin (at the time of hypoglycemia 88.8 microU/ml; normal, 5 - 35 microU/ml) and C-peptide levels (at the time of hypoglycemia 6.1 ng/ml; normal, 1.37 - 3.51 ng/ml), markedly increased serum calcitonin concentration (481 pg/ml; normal, < 9.9 pg/ml), and an enlarged residual thyroid gland. Aspiration biopsy of the thyroid was negative for parafollicular C-cell hyperplasia or medullary thyroid carcinoma. Abdominal ultrasound and CT scan revealed a tumor in the head of the pancreas, which was surgically removed. Histopathological evaluation of the pancreatic tumor showed typical features of a neuroendocrine neoplasm with strong immunostaining for both insulin and calcitonin. After removal of the pancreatic tumor, clinical symptoms resolved and biochemical markers normalized (serum insulin, 14.9 microU/ml; C-peptide, 3.0 ng/ml; calcitonin, 2.9 pg/ml) confirming the causal relationship between insulinoma and markedly increased serum calcitonin levels.