A thyroid testing algorithm: results of a pilot study.

We conducted a pilot study to evaluate an algorithm for thyroid function testing consisting of initial serum thyrotropin values, measured by a sensitive immunoradiometric assay (TSH-IRMA), followed by a computer-directed decision to order further studies. We divided 216 outpatients according to their serum TSH-IRMA values as follows: suppressed (less than 0.1 mU/L, group I); low (0.1 to 0.4 mU/L, group II); normal (0.5 to 5.0 mU/L, group III); and high (greater than 5.0 mU/L, group IV). Thyroxine (T4), resin uptake (RU), and free thyroxine index (FTI) tests on groups I, II, and IV revealed that T4 and RU were normal for most patients in all groups and FTI was normal in 80% of group I, 93.4% of group II, and 93.3% of group IV. All patients in group I were designated hyperthyroid from either an exogenous or endogenous source. All patients in group II were clinically euthyroid except one; 50% were taking either L-thyroxine or propylthiouracil and 50% had no identifiable thyroid disease. Patients in group IV were hypothyroid. Overall, TSH was more effective in detecting both hypothyroidism and hyperthyroidism than either serum T4, RU ratio, or both combined in FTI since results of these measures fell in the normal range for most patients in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)