[Thyroid biological evaluation: critical study].

Laboratory tests to assess thyroid gland function have changed considerably over the past few years, with the development of techniques allowing for the direct routine determination of unbound thyroid hormones (tri and tetra-iodothyronine), the "ultra-sensitive" assay of serum concentrations of TSH (thyroid-stimulating hormone) and finally, the radioimmunological assay of anti TSH-receptor antibodies. In our study, which excluded patients having an excess of iodine or who had serious disease of an organ other than the thyroid, we assessed the impact of these parameters respectively on various disease categories. An innovation has been made in that anti TSH-receptor antibody assay is now possible in everyday practice while up to the present this was only possible in the hospital setting and with a limited number of cases: this titer is important as a classification parameter in diagnosing Grave's disease and has prognostic importance to monitor treatment of patients suffering from this disorder. The "ultrasensitive" version of measuring thyrotropic hormone requires a new strategy: TSH assessment becomes the first-line diagnosis test to evaluate thyroid function because it differentiates from control subjects, as well as patients with hyper ou hypothyroidism who are not receiving therapy. In other cases, dosing of the free hormones T3 and T4 remains a vital supplementary test.