Endocrine Abstracts

Background: Familial hypocalciuric hypercalcaemia (FHH) is a rare benign autosomal dominant condition which causes life-long mild to moderate hypercalcaemia. It is usually underdiagnosed due to lack of symptoms in majority of patients and low rate of screening even among endocrinologists. Recent NHS England National Genomic Directory testing criteria for FHH recommend testing patients presenting with hypercalcaemia and calcium creatinine clearance ratio (CCCR) <0.02.

Methods: We report 10 patients diagnosed with FHH in Birmingham Heartlands Hospital metabolic bone clinic from 2017 to 2023. Data was collected using local patients database.

Results: In our cohort, mean age at the genetic diagnosis of FHH was 50 years, 8 patients were females, most were asymptomatic and all but one had hypercalcaemia discovered on routine blood test. One woman presented with recurrent renal stones. The mean calcium level at the diagnosis was 2.84mmol/l, mean PTH 7.95 and mean Vitamin D level was 55.7 nmol/l. The calculated mean urine CCCR was 0.0055. There was an average delay of 4.5 years from the referral to time of genetic diagnosis. Therefore, 70% of the patients were initially presumed to have primary hyperparathyroidism. Seven out of 10 patients had parathyroid ultrasound and CT of the neck performed. 3 patients has also Sestamibi scan. All of them had renal ultrasound and bone density scan, and one had renal stone and another osteoporosis. Two cases were diagnosed after having parathyroid surgery and persistent hypercalcaemia triggered genetic testing.

Conclusion: FHH remains largely underdiagnosed. Normal PTH in context of hypercalcaemia should prompt FHH screening. An early diagnosis reduces patient’s anxiety, cost of unnecessary imaging and surgery.