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Basal TSH levels compared with TRH-stimulated TSH levels to diagnose different degrees of TSH suppression: diagnostic and therapeutic impact of assay performance
JournalArticle (Originalarbeit in einer wissenschaftlichen Zeitschrift)
ID
3975340
Author(s)
Christ-Crain, M.; Meier, C.; Roth, C. B.; Huber, P.; Staub, J. J.; Muller, B.
Basal TSH levels compared with TRH-stimulated TSH levels to diagnose different degrees of TSH suppression: diagnostic and therapeutic impact of assay performance
Journal
European Journal of Clinical Investigation
Volume
32
Number
12
Pages / Article-Number
931-7
Keywords
Administration, Intranasal; Administration, Oral; Adult; Aged; Female; Humans; Hyperthyroidism/blood/*diagnosis; Immunoassay/methods; Male; Middle Aged; Sensitivity and Specificity; Thyroid Function Tests; Thyrotropin/*blood; Thyrotropin-Releasing Hormone/*diagnostic use
Abstract
BACKGROUND: The estimated prevalence of endogenous subclinical hyperthyroidism varies from 4% to 6% and a basal thyroid stimulating hormone (TSH) level 0.03 mIU L-1) or two third generation assays (functional sensitivity 0.01 mIU L-1 and 0.007 mU L-1, respectively). Serum TSH concentration was determined before and 3 h after oral administration of 40 mg of TRH and before and 30 min after nasal administration of 2 mg of TRH. RESULTS: In the oral testing group, the basal TSH levels measured by the different TSH assays were 0.06 +/- 0.03, 0.04 +/- 0.02 and 0.03 +/- 0.02, respectively, whereas the peak TSH levels were 0.4 +/- 0.6, 0.4 +/- 0.6 and 0.3 +/- 0.5 in the patients with subclinical hyperthyroidism. In overt hyperthyroidism, the basal TSH levels were 0.06 +/- 0.02, 0.03 +/- 0.02 and 0.03 +/- 0.02, whereas the peak TSH levels were 0.19 +/- 0.3, 0.16 +/- 0.3 and 0.15 +/- 0.2, respectively. Basal TSH values could discriminate between different degrees of TSH suppression if measured with a third generation assay (P > 0.001), but not with a second generation assay. There was only a weak correlation between basal TSH and peak TSH when measured by a second generation assay (n = 126; r = 0.3; P > 0.001) in contrast to the strong correlation found using the third generation assays (n = 128; r = 0.7; P > 0.001 and n = 69; r = 0.8; P > 0.001, respectively). CONCLUSIONS: In view of the recent concerns about potential adverse effects in TSH suppression and based on our data, it is mandatory to select a TSH assay with a functional sensitivity of > or = 0.01 mIU L-1 for optimal titration of L-T4 suppressive therapy, especially in patients with thyroid cancer. If, however, only a second generation TSH assay is available, additional TRH testing allows a more careful titration of suppressive thyroxine therapy.
