THYROID FUNCTION TESTS; INTERPRETATION
There have been considerable improvements in assays for thyrotropin (TSH), free T4, and free T3 over the past 20 years. As a result, interpretation of thyroid function tests is now generally straightforward, and more than 90% of people investigated are diagnosed with normal thyroid gland function. However, there remain a few situations in which the results of TSH, free T4, and free T3 assays tend to point in different directions, as well as cases in whom thyroid function test results seem clear cut but are in fact misleading. Additionally, over the past 6 years, an increasing number of genetic defects has been identified in the pituitary-thyroid axis. These defects are easily misdiagnosed by the unwary and, although rare, can present for the first time in adulthood, with implications for both the patient and their family. My aim is to guide the general physician around these pitfalls with a practical approach.
Lancet 2001; 357: 61924
University Department of Medicine, Bristol Royal Infirmary, Bristol
BS2 8HW, UK (C M Dayan FRCP)
(now at Cardiff as Prof of Endocrinology)