Abstract
Severe hypercalcaemia is usually due to either neoplastic disease or primary hyperparathyroidism. Rarer causes do exist, and exceptionally these may occur concomitantly. We describe the case of a 45-year-old man who presented in a debilitated state with severe hypercalcaemia (total serum calcium 3·56 mmol/L, albumin 35 g/L) and suppressed serum parathyroid hormone concentration. It was initially suspected that he had neoplastic disease, but routine thyroid function tests demonstrated evidence of thyrotoxicosis [thyroid-stimulating hormone <0·05 mU/L (0·15-3·5); free thyroxine 75 pmol/L (8-27); total tri-iodothyronine 7·0 nmol/L (1·0-2·6)], which was probably secondary to a silent or subacute thyroiditis. After extensive investigation, it was established that the patient also had isolated adrenocorticotrophic hormone deficiency, presumably secondary to lymphocytic hypophysitis. Glucocorticoid therapy resulted in a dramatic improvement in the patient's clinical state and 1 year later he remained euthyroid and normocalcaemic.