Thyrotropin radioimmunoassays: birth, life, and demise

Thyrotropin (thyroid-stimulating hormone; TSH) radioimmunoassays had their origin in 1965. For 20 years, they provided the single most important measurement for the diagnosis and treatment of hypothyroidism. Many improvements in the techniques of radioimmunoassay were applied to TSH measurements. These improvements provided greater specificity and sensitivity, but the assay was cumbersome and time-consuming. Despite these disadvantages, considerable information about the relationship of the hypothalamus, pituitary, and thyroid in normal and abnormal conditions was derived. The advent of monoclonal antibody technology and its application to the glycoprotein hormones resulted in the development of epitope-specific antibodies. These antibodies allowed a "sandwich" configuration for the TSH assay, which resulted in a new era of specificity, sensitivity, and speed in TSH measurements.