A hormone-secreting tumour that can occur in the adrenal glands. Phaeochromocytomas usually develop in the small glands on top of the kidneys (adrenal glands). They most commonly affect people between the ages of 20 and 50, but can occur at any age. Because of hormones secreted, symptoms include high blood pressure, sweating, rapid heartbeat and headache. Surgery to remove the tumour is usually required.