Unaccountable severe hypercalcemia in a patient treated for hypoparathyroidism with dihydrotachysterol

This report describes a forty-seven-year-old female patient with a complex medical history. She was suffering from an unspecified interstitial lune di sease, papillary thyroid carcinoma which had been treated, hypoparathyroidi sm after thyroidectomy for which she was receiving dihydrotachysterol and c alcium, and atrial fibrillation and congestive heart failure as a result of mitral stenosis. Shortly after mitral valve replacement she developed a se vere hypercalcemia (serum calcium 5.9.5 mmol/l) during a febrile illness. A t that time anti-tuberculous agents were also being administered fur presum ed tuberculosis. The possible mechanisms for this severe elevation of the c alcium level are discussed. Immobilization, while Paget's bone disease was present, and perhaps enhanced activation of dihydrotachysterol by rifampici n, could have led to increased calcium-release into the circulation. Contin uous suppletion of calcium and vitamin D, provoked dehydration and the mech anism of the milk-alkali syndrome also contributed to this extremely high c alcium level. It is concluded that hypoparathyroid patients bring treated w ith vitamin D and calcium should be carefully monitored in the case of an i ntercurrent illness or a change in medication. (C) 1999 Elsevier Science B. V. All rights reserved.