title: [Does the determination of basal TSH level replace the TRH test?].
abstract: With the help of the newly developed "supersensitive" assays for thyrotropin it is possible to determine concentrations down to 0.03 mU/l. Patients with a manifest hyperthyroidism show, as a rule, very low TSH levels and they react not at all or only very weakly to TRH stimulation. Therefore, various authors have claimed that estimation of the basal TSH level is sufficient as a screening test for the exclusion of a hyperthyroidism. To check the reliability of this statement we determined the reference interval of the parameter "basal TSH". It is a log-normal distribution; the reference interval of healthy people (95. percentile) is 0.25-4.0 mU/l. The TSH response to TRH stimulation also follows a log-normal distribution, the reference interval being 3.0-20 mU/l. There is a poor correlation between both parameters (r = 0.83). Histograms of populations with reduced, normal, or increased reactivity to TRH stimulation show broad overlapping zones. A valid prediction (with a plausibility greater than 90%) of the TSH response to TRH stimulation is therefore possible in the extreme ranges only (less than 0.2 mU/l for reduced, greater than 5 mU/l for increased reactivity respectively). In between there is a wide "gray zone", where reliable prediction is not possible on the basis of laboratory data only (without clinical findings).
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D013972:Thyrotropin / Q000097:blood*; D013973:Thyrotropin-Releasing Hormone
chemical_list: D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin
vernacular_title: Ersetzt die Bestimmung der basalen TSH-Konzentration den TRH-Test?