[Diagnostic applications of laboratory tests in primary medical practice endocrine disorders]

The diagnostic steps for endocrine disorders have been complex mainly because abnormalities in more than one endocrine organ often coexist in a single patient. Also, endocrine disorders are diverse and it is hard to cover them all here. I have defined the initial tests and additional tests to confirm the initial diagnosis in the two endocrinopathies; Basedow's disease as a representative of relatively common diseases and pheochromocytoma as an example of uncommon disorders. Abnormalities in routine laboratory test results such as hypocholesterolemia in hyperthyroidism can provide some clues to the diagnosis of endocrine disorders. Initial tests for suspected Basedow's disease would be free or total T4 and TSH. In addition, free or total T3 and TRAb will be included under some circumstances. Although uncommon, the diagnosis of pheochromocytoma should be considered in patients with paroxysmal symptoms and in hypertensive patients not responding well to conventional therapy. As an initial step for screening this disorder, I would recommend to determine 24h urinary catecholamine levels (adrenaline, noradrenaline and metanephrine). When abnormally high test results have been obtained, the tumor must be located in order to facilitate its surgical removal. CT and MIBG scintigraphy are of value in identifying these tumors. When localization of tumors by imaging diagnosis is unsuccessful, analysis of blood samples obtained via percutaneous venous catheterization will help establish the diagnosis. These guidelines are still preliminary and are open for critical discussion.