Use of a single TSH-measurement after oral thyrotrophin releasing hormone: an economical and highly sensitive thyroid screening test.

The increment of serum TSH after thyrotrophin-releasing hormone (TRH) is usually considered an extremely sensitive thyroid test, particularly useful in borderline disturbances. We evaluated 195 patients by measuring serum TSH before and 3 h after 40 mg TRH po, and by various other thyroid tests. We found a very tight correlation between the TSH- increment and the 3 h TSH. Thus the TSH-increment can reliably be estimated from the 3 h TSH. The mann-Whitney test confirmed that the 3 h TSH identified thyroid dysfunction as well as the TSH-increment. The basal TSH can therefore be omitted and we propose the measurement of the 3 h TSH as an initial screening test. This single measurement economically excludes the many euthyroid patients sent for thyroid evaluation from further costly tests.