NAPLEX Practice Question # 62

NAPLEX Examination.

Practice Question # 62.



fourth-generation sensitive TSH assay

Serum thyrotropin (TSH) assays

  • This test is the most sensitive test for detecting the hypothyroid state because the hypothalamic– pituitary axis compensates very quickly for even slight decreases in circulating free hormone by releasing more TSH. Th e TSH levels may be elevated even before low circulating levels of serum total T4 are detectable by diagnostic testing. The early TSH assay used radioimmunoassay (RIA) methodology.
  • The sensitivity of the assay has improved since, moving to the use of monoclonal antibodies in the late 1980s. Nomenclature established by the American Thyroid Association (ATA) has classified the improvement in sensitivity based on the lower limit of detection. The new classification follows a generational format.

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