My doctor has ordered a clonidine suppression test. where can i find information about this?

Adrenal Tumor test: Clonidine suppression test is used to diagnose a particular adrenal gland tumor called pheochromocytoma. In this tumor, adrenal glands produce excessive catecholamines (adrenaline, noradrenaline and metanephrines). Clonidine lower blood levels of catecholamines but if a tumor is present, catecholamine levels do not decrease when Clonidine is given. Best site to learn about this is medlineplus.Gov.