Introduction
Severe hypocalcemia due to avid osteoblastic bone metastases is a rare occurrence that has been reported to occur in less than 1% of patients with metastatic prostate carcinoma.1 We report a case of severe refractory hypocalcemia due to osteoblastic bone metastases that was successfully managed with steroids.
Case Description
A 73 year old male with osteoblastic metastases from advanced prostate carcinoma was admitted for lower limb weakness due to spinal cord compression from bony metastases. During admission, he had severe symptomatic hypocalcemia, a low ionised serum calcium of 0.9 mmol/l, low serum phosphate of 0.76 mmol/L and elevated intact parathyroid hormone of 21.8 pmol/L. Serum creatinine, magnesium and 25-hydroxy vitamin D levels were normal. His alkaline phosphatase (ALP) was markedly elevated at 5214 U/L. His hypocalcemia persisted despite a continuous calcium infusion and high doses of oral calcium carbonate and calcitriol. Eventually, the use of intravenous methylprednisolone (1mg/kg) normalized the patient’s serum calcium after two doses.
Discussion
In patients with osteoblastic bone metastases, an increase in bone formation leads to increased influx of calcium into osteoblastic bone. This results in development of hypocalcemia.2 Hypocalcemia due to osteoblastic bone metastases is frequently refractory to usual treatment with calcium, vitamin D and vitamin D analogues3 because of ongoing calcium uptake by osteoblastic metastases and parathyroid hormone which stimulates proliferation of osteoblastic bone metastases.
Given the action of glucocorticoids on reducing osteoblast number and function, methylprednisolone was used in our patient to treat hypocalcemia associated with osteoblastic prostate carcinoma. A rapid response to intravenous methylprednisolone was seen in our patient. To our knowledge, the is the second case report on successful use of methylprednisolone in management of a patient with severe, refractory hypocalcemia due to osteoblastic bone metastases.4