Development of hungry bone syndrome after rapid lowering of PTH with intravenous maxacalcitol therapy in a patient with non-uremic secondary hyperparathyroidism.

A 41 year-old woman complained of general bone pain and polyuria. She did not have Albright hereditary osteodystrophy. Laboratory examination revealed hypokalemia, hypocalcemia, and an elevation of serum intact PTH concentration. The patient was polyuric and relatively hypercalciuric, though her glomerular filtration rate (GFR) was normal. Neither urinary Pi nor cAMP excretion was remarkably promoted by an exogenous PTH load. An iliac bone biopsy revealed osteopenia, active osteoclastic bone resorption, fibrous transformation in bone marrow tissue, and severely disturbed calcification. Although the oral administration of alfacalcidol showed no effects, 3 weeks of intermittent intravenous injection of maxacalcitol therapy decreased the serum intact PTH concentration from 597 pg/ml to 40 pg/ml, and the bone pain was greatly relieved. However, plasma Ca concentration also decreased and symptoms of tetany appeared. Pseudohypoparathyroidism type Ib was the most likely diagnosis in this patient. In conclusion, maxacalcitol therapy satisfactorily suppressed parathyroid function in a patient with secondary hyperparathyroidism without uremia. Appropriate Ca supplementation was required to perform it safely.