Extreme hypercalcemia due to a giant parathyroid adenoma

Background/objective

Primary hyperparathyroidism is the most common cause of hypercalcemia. Hypercalcemia secondary to giant parathyroid adenomas and parathyroid carcinomas share substantial clinical similarities and their differentiation is challenging.

Case report

We present the case of a 72-year-old female with profound lethargy and confusion associated with polydipsia and polyuria, who was found to have an extremely elevated serum calcium level of 18.3 mg/dL (normal 8.4–10.5 mg/dL), ionized calcium 2.56 mmol/L (normal 1.20–1.32 mmol/L) and intact parathyroid hormone of 1838 pg/mL (normal 15–65 pg/mL). Ultrasound revealed a large hypoechoic nodule measuring 2.5 x 1.8 × 2.0 cm located in the right thyroid bed. Computed tomography revealed a hypoattenuating mass in the same region without obvious soft tissue invasion or lymphadenopathy. Technetium-99 m sestamibi with single-photon emission computed tomography identified intense focal radiotracer uptake at the same location most consistent with hyperfunctional parathyroid tissue. Patient underwent surgical exploration and resection of a parathyroid mass, which weighed 12.1 g and measured 4.6 x 2.5 × 1.8 cm. Pathology confirmed a diagnosis of benign parathyroid adenoma. Patient's laboratory values normalized and her mental status improved significantly, and she was discharged in stable condition.

Discussion

This is a rare case of a symptomatic patient with extreme primary hyperparathyroidism and hypercalcemia that was found to have a benign giant parathyroid adenoma, rather than carcinoma.

Conclusion

Differentiation between large hyperfunctioning parathyroid adenoma and parathyroid carcinoma is nontrivial due to shared characteristics of each. Therefore, the final diagnosis requires imaging and histopathological examination.