LONG-ACTING THYROID STIMULATOR OF GRAVES DISEASE

A long-acting thyroid stimulator (LATS), distinct from pituitary thyrotropin (TSH), is found in the serum of some patients with Graves' disease. Although serum LATS levels correlate with several parameters of thyroid activity in thyrotoxicosis, the role of this abnormal stimulator in the pathogenesis of Graves' disease remains uncertain. High levels of LATS are frequently associated with pretibial myxedema but the relation of LATS to the ophthalmopathy of Graves' disease is less clear. Demonstration that LATS is an immunoglobulin G (IgG) and evidence that the distribution of thyroid-stimulating activity in the polypeptide chains of the IgG parallels antigen-binding activity in known antibodies has led to speculation that LATS is an antibody to thyroid antigen(s). The evidence for and against this hypothesis is discussed in detail and it is concluded that present information is insufficient to confirm or disprove this postulate. Although both in vivo and in vitro studies indicate that LATS and TSH act on the same thyroidal site(s), the precise mechanism of action of these thyroid stimulators has not yet been determined. © 1968.