Recent Developments in the in vitro Bioassay of TSH and Thyroid­ Stimulating Antibodies

Circulating immunoglobulins with thyroid-stimulating activity were originally discovered 30 years ago1. These thyroid-stimulating antibodies (TSAb) are now established as important pathogenetic factors in the hyperthyroidism of Graves’ disease. They appear to interact with a site on or close to the TSH receptor and generally mimic the bioactivity of TSH. It has now become apparent that another group of related antibodies may specifically or preferentially stimulate thyroid growth as opposed to differentiated function, and these are discussed in Chapter 3. Such antibodies are now referred to as thyroid growth-stimulating antibodies, or TGAb. In the present chapter we will largely be concerned with recent developments in techniques to measure antibodies which hitherto have been regarded as stimulators of differentiated function leading to the excess production of thyroid hormones. These continue to be referred to as TSAb as opposed to TGAb.