Endocrine Abstracts

History: The coexistence of primary hyperparathyroidism and familial hypocalciuric hypercalcemia is exceedingly rare. We present the case of a young woman in her thirties who presented with hypercalcemia detected on routine blood tests. She had no significant medical or family history of hypercalcemia.

Investigations: Her serum calcium was consistently around 3.2 mmol/l, with elevated parathyroid hormone levels at 110 ng/l. Phosphate was low at 0.52 mmol/L and vitamin D levels were normal.

Management: She was initially treated with intravenous fluids as an inpatient and started on Cinacalcet, with plans for outpatient follow-up. She continued Cinacalcet and underwent localisation studies with a Sestamibi scan and neck ultrasound. Scans revealed no parathyroid adenomas. The urine calcium creatinine clearance ratio excluded familial hypocalciuric hypercalcemia (FHH). The serum calcium remained high at 2.94 mmol/l. She underwent bilateral neck exploration/parathyroidectomy - it showed two parathyroid lipoadenomas, which were resected. Post-operatively, her calcium remained high, and Cinacalcet was restarted. Genetic testing results were negative for MEN-1, but the testing confirmed a diagnosis of FHH. The choline PET-CT and CT 4D parathyroid scan failed to show evidence of additional parathyroid adenomas. Long-term options included continuing Cinacalcet or considering repeat surgery. The patient opted for repeat surgery to pursue a definitive cure for her hypercalcemia and avoid the long-term use of Cinacalcet as she was planning for future pregnancies.

Conclusion: This case highlights the complexities in diagnosing and managing concurrent primary hyperparathyroidism and familial hypocalciuric hypercalcemia. The urine test results were not suggestive of FHH and therefore were misleading in this case. This case also emphasises the need for a multidisciplinary team approach in managing complex cases of this nature.