[Diagnosis: hyperparathyroidism simulating dementia]

A patient is described who was admitted to the geriatric department under the diagnosis: 'dementia'. We found more than once a rise of the calcium level in th serum. The level of parathormon was 15 times as high as normal. CT scanning of the neck showed a structure which was found to be an adenoma during exploration. After the operation, the calcium level normalised and the 'dementia' vanished.