Severe hypercalcaemia secondary to isolated adrenocorticotrophic hormone deficiency and subacute thyroiditis

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.