Thyroid function tests. Guidelines for interpretation in common clinical disorders.

While a wide variety of thyroid function tests are currently available, all are sometimes abnormal in patients without thyroid disease. To interpret test results properly, the clinician needs to be aware of factors altering thyroid function tests. In every instance, the clinician needs to begin by asking whether the patient is thyrotoxic or hypothyroid and then should order a test to substantiate or exclude the diagnosis. In this way, accurate and early diagnosis of thyroid dysfunction can be routinely established.