[Strategy for the diagnosis of thyrotoxicosis (author's transl)].

A study carried out on 808 patients examined because hyperthyroidism was suspected has shown that the most discriminating thyroid test is the free thyroxin index (FT4) in the plasma. For about 70% of the patients the comparison between the clinical diagnosis made by a clinician at his first interview and the results of FT4, leads one to an accurate assessment of the thyroid function. For the remaining 30% of the patients the assay of triiodothyronin (T3) in the plasma is the best laboratory test; it enables a diagnosis in 20% of those patients. It is therefore only in about 10% of the patients that more sophisticated laboratory tests would be necessary, such as TRH stimulation test and a technetium uptake whenever a scintigraphy is performed. Scintigraphy with technetium is only required to look for a possible toxic adenoma. In summary such a decision tree makes it possible to reduce considerably the cost of the diagnosis.