Endocrine Abstracts

Background: Primary hyperparathyroidism is the commonest cause of hypercalcemia. Current guidelines advise to rule out familial hypocalciuric hypercalcemia (FHH) when evaluating hypercalcemia. It is widely considered that FHH is associated with low urine calcium creatinine clearance ratio (CCCR). However, low CCCR can also occur in Primary hyperparathyroidism.

Case: A 30 years lady presented with hypercalcemia and high parathyroid hormone (PTH). She had a past history of primary hypothyroidism, previous secondary amenorrhea, anxiety and depression. Her urine CCCR was low. However, dual energy X-ray absorptiometry (DEXA) scan showed evidence of osteopenia. In view of bone involvement, primary hyperparathyroidism was considered. She was treated with Cinacalcet 30 mg BD and underwent surgical removal of 3 parathyroid glands. Histology showed mild hyperplasia. Post-surgery, the calcium and PTH level became normal and a repeat DEXA scan showed normal bone density. Her low urine CCCR though was contrary to the diagnosis of primary hyperparathyroidism. Her father was later diagnosed with hypercalcemia and so she underwent genetic testing which showed FHH related CaSR gene mutation. She thus had both conditions coexisting.

Conclusion: Current guidelines recommend measuring urine CCCR to exclude FHH. However, the coexistence of FHH and primary hyperparathyroidism should be considered in patients with hypercalcemia, elevated parathyroid hormone levels, and low urinary calcium excretion with end-organ involvement. Surgical intervention isn’t normally indicated in FHH. However, in this case it helped to reduce the degree of hypercalcemia, alleviate symptoms, and improve the bone density.