[Severe hypercalcemia during hyperthyroidism].

A particularly high hypercalcemia (141 mg/ml) was observed in a man with Graves' disease. An intense muscle asthenia, with lack of dynamism and vomiting which may cause dehydration, are the most suggestive signs of hypercalcemia. Bone biopsy and above all parathormone estimations permit one to eliminate associated hyperparathyroidism. The efficacy of mithramycin used alone, without any other hypocalcemic drug, was remarkable. The direct responsibility of thyrotoxicosis as a cause of the calcium disorder seems undoubted but the precise mechanism of the hypercalcemia remains unexplained.