ASSESSMENT OF BASAL AND STIMULATED TSH IN THE DIAGNOSIS OF OVERT AND SUBCLINICAL HYPERTHYROIDISM

A TRH test was performed in 171 consecutive patients with a TSHbasal b elow the reference range. TSHbasal, TSHstimulated and Delta TSH were d etermined and compared, using assays of the second and third generatio n. Free thyroid hormones were elevated in 48 and normal in 123 patient s. The sensitivity of all evaluated parameters to assess overt hyperth yroidism was between 94 and 98% with both assays, using a defined TSH threshold (mean of patients with overt hyperthyroidism + 2 standard de viations). However, specificity was much lower, only 34 and 23%, respe ctively, for the TSHbasal. Significant improvement followed TRH-testin g: specificity rose to 63 and 57%. The superior reproducibility of TSH values in the lower range, using the third generation assays, was of little value in the differentiation between subclinical and overt hype rthyroidism.