Endocrine Abstracts

Background: Hypercalcemia may stimulate thyroid’s C-cells to produce the calcitonin, that could lead to misdiagnosis of medullary thyroid cancer.

Clinical case: A 47-year-old woman suffered from fracture of the left knee. She could not walk and used a wheelchair. CT scan in a public hospital detected multiple bone lytic changes in the ribs and vertebrae (mts?), tumor in the liver (mts?) and node in the thyroid gland 2.6*1.9 cm. Thyroid biopsy showed follicular neoplasia (cancer?). At the same time, blood analysis showed high level of serum calcitonin 190 pg/m (0–5.5). Thus, her state was determined as the medullary thyroid cancer (MTC) with mts in bone and liver and she was sent to our center for surgery of MTC.

Medical examination uncovered primary hyperparathyroidism (PH): total calcium – 3.78 mmol/l (2.10–2.55), PTH −1513 pg/ml (15–65) in combination with 3.7*2.9*2.4 cm tumor behind the thyroid gland showed by the US exam. Osteitis fibrosa cystica was suspected after radionuclide bone imaging. Renal functions were impaired, GFR 10 mL/min/1.73 m². Given the fast progress of the disease the parathyroid cancer (PC) was suspected, so “en bloc” removal of the tumor was performed. The diagnosis was confirmed by histological examination. PTH, total serum calcium levels as well as calcitonin were decreased down to the reference level after the surgery. The liver biopsy shows no tumor cells. PET/CT did not observe the abnormal accumulation of 18FDG in the liver and in bones. The patient’s condition has significantly improved 4 month after the surgery – she can walk without a wheelchair.

Conclusions: High level of calcitonin caused by hypercalcemia in combination with nodules in the thyroid gland can lead to incorrect diagnosis. It is important to exclude hypercalcemia in case of high levels of calcitonin.