Does familial hypocalciuric hypercalcaemia (FHH) ever require a parathyroidectomy?
A raised calcium level in the blood due to primary hyperparathyroidism is a potentially life-threatening condition affecting the bones, heart, kidneys, brain and other organs. However there is another disorder called familial hypocalciuric hypercalcaemia (FHH), a rare, lifelong, benign disease which is often confused
with other conditions which cause a raised calcium, such as hypercalcaemia of malignancy and primary hyperparathyroidism. It is important to distinguish this disease, as it does not require any treatment and is not cured by parathyroidectomy.
One problem encountered by parathyroid surgeons from time to time is that a patient with FHH may be diagnosed by their endocrinologist as having primary hyperparathyroidism and is referred for surgery anyway. The result of such an operation in those circumstances is that four normal parathyroid glands are found and the calcium remains high after the operation. The two conditions can often be correctly diagnosed by checking the amount of calcium excreted in the urine using the 24 hour urinary calcium/creatinine ratio, however this is not an absolutely accurate test as 20% of patients with FHH may intermittently have an elevated ratio (above 0.01), and occasional patients with primary hyperparathyroidism will have a suppressed ratio. The only absolute test for FHH is genetic testing for the CaSR gene which can be performed by referral to a Familial Genetics Clinic. This is not routinely performed for all patients with primary hyperparathyroidism due to cost, however a recent expert review by Dr Christensen and colleagues suggested that all patients with a ratio of less than 0.02 should undergo routine testing.
Whilst FHH is not life threatening, some patients do experience similar neurologic and neuromuscular symptoms to those with primary hyperparathyroidism. Importantly once a patient has been diagnosed with FHH, all family members should also undergo genetic testing as that will allow them to avoid an unnecessary parathyroidectomy should the calcium levels in their blood ever be tested.