TSH assay “quality” has historically been defined by clinical sensitivity—the ability to discriminate between hyperthyroid and euthyroid TSH concentrations.33 This lack of sensitivity initially led to the use thyrotropin releasing hormone (TRH) administrations to obtain TSH concentrations into the measurable range for the detection of subclinical hypothyroidism and hyperthyroidism.10,34. Here, TRH is linked to hyperthyroidism.