Familial hypocalciuric hypercalcemia: Recognition among patients referred after unsuccessful parathyroid exploration

Of 67 patients referred after unsuccessful surgery for presumed primary hyperparathyroidism, 6 were shown to be members of kindreds with familial hypocalciuric hypercalcemia. This diagnosis had not been recognized in any of the 6 previously. Most of the remaining 61 cases had proven or probable typical primary hyperparathyroidism, and a subgroup of 4 had hypercalcemia with suppression of the parathyroid glands. Urine calcium excretion expressed as the calcium:creatinine clearance ratio provided an easily measurable and effective index to separate the groups with familial hypocalciuric hypercalcemia, typical primary hyperparathyroidism, and suppressed parathyroids. Thus, at least 9% of patients referred after unsuccessful parathyroidectomy had familial hypocalciuric hypercalcemia. The assessment of urine calcium excretion by indices such as the calcium:creatinine clearance ratio should facilitate recognition of this condition, which responds poorly to standard subtotal parathyroidectomy.