New Sensitive lmmunoradiometric Assays for Thyrotropin

Excerpt

Thyrotropin (TSH) is the pituitary hormone that regulates thyroid hormone production; thyroid hormone feedback to the pituitary gland suppresses the secretion of thyrotropin. Since the 1970s, an elevated serum thyrotropin concentration measured by radioimmunoassay (RIA) has been used to discriminate between primary hypothyroidism and euthyroidism. Patients with early thyroid failure (subclinical hypothyroidism) have elevations in serum thyrotropin levels before serum thyroxine levels fall below the normal range. In patients with hyperthyroidism, thyrotropin should be suppressed; however, conventional thyrotropin-RIA methods have detection limits of 1 to 2 µIU/mL, whereas euthyroid persons frequently have serum thyrotropin concentrations of below 1 µIU/mL. Modified