Thyroid function tests: a review.

In this paper, we review the tests that are executed to aid the diagnosis of thyroid dysfunction. Thyroid function tests provide information at physiological, pathological and anatomical levels. Along with history and physical examination they owe to many specific findings that are associated with thyroid functioning. So an attempt has been made to put forward a gist of thyroid function tests. Serum tests of thyroid function are serum total thyroxine (T4), serum total triiodothyronin (T3), free thyroxine (FT4), free triiodothyronin (FT3), reverse triiodothyronin (rT3), thyroid stimulating hormone (TSH), serum calcitonin and protein thyroglobulin (Tg). The serological tests are antithyroglobulin antibodies (ATA) and antimicrosomal antibodies (AMA). An invasive test for histologic examination is done by fine needle aspiration cytology (FNAC) and noninvasive test includes ultrasonography, magnetic resonance imaging, and positron emission tomography. Further molecular study provides molecular markers for thyroid cancer. These tests can provide greater sensitivity and specificity that enhance the likelihood of early detection of ambiguous thyroid disease with only minimal clinical findings. Lastly, in vivo tests are thyroidal radioiodine and iodide uptake is also done.