Endocrine Abstracts

Introduction: Primary hyperparathyroidism is typically caused by a parathyroid adenoma (80-85% of the cases). Very rare causes are represented by parathyroid carcinoma and atypical parathyroid adenoma (0.5-1.5% of the cases). Atypical parathyroid adenomas have atypical histological features, not sufficient to be considered a carcinoma, and have an uncertain malignant potential and risk of recurrence. We report the case of a 66-year-old man referred from another medical center for severe hypercalcemia (14.41 mg/dl) with normal serum phosphate (3.24 mg/dl) and elevated PTH (1376 pg/ml - 20 fold of the normal level). The patient mentioned bilateral gonalgia and bone pain for 5 years. His personal history revealed permanent atrial fibrillation, class II congestive hearth failure and bilateral nephrolitiasis. Laboratory evaluation showed a highly elevated serum calcium (13.7 mg/dl), and PTH (1128 pg/ml) with normal serum vitamin D level, confirming the diagnosis of primary hyperparathyroidism. Screening for multiple endocrine neoplasia was negative. The cervical ultrasound revealed the presence of a 4.13/2.27 cm hypoechoic image, posterior to the left thyroid lobe, which deviated the trachea, suggestive of a left inferior parathyroid adenoma. Cervical CT scan revealed a 2.6/3.5/5.7 cm nodular heterodense process in contact with the left thyroid lobe. T scores of right femur (-1.1 SD) and distal radius (-1.3 SD) on osteodensitometry showed osteopenia. The patient received intravenous furosemide and bisphosphonate therapy to control the hypercalcemia before he was referred to the surgery department for left inferior parathyroidectomy. After surgery PTH levels dropped significantly (24.83 pg/ml), but 4 months after surgery PTH levels increased (387.5 pg/ml) with normal calcium level (8.9 mg/dl). Histopathological exam concluded to atypical features of the adenoma that were suggestive but not diagnostic of parathyroid carcinoma.

Conclusion: The diagnosis and management of the atypical adenoma is still challenging because there are no specific guidelines for the follow-up of patients after parathyroid surgery. Although low, there is a risk of recurrence that can occur many years after initial presentation, so long-term yearly monitoring of calcium concentrations after the surgery is recommended. Once the histopathological diagnosis has been confirmed, studies suggest that immunohistochemistry may be a good approach in differentiating between benign and malignant parathyroid masses.