The clinical use of thyroid function tests. 
Laboratory tests are essential for accurate diagnosis and cost-effective management of thyroid disorders.  When the clinical suspicion is strong, hormonal levels just confirms the diagnosis.  However, in most patients, symptoms are subtle and unspecific, so that only biochemical tests can detect the disorder.  The objective of this article is to do a critical analysis of the appropriate use of the most important thyroid function tests, including serum concentrations of thyrotropin (TSH), thyroid hormones and antithyroid antibodies.  Through a survey in the MedLine database, we discuss the major pitfalls and interferences related to daily use of these tests and recommendations are presented to optimize the use of these diagnostic tools in clinical practice.