TSH binding by globulins from patients with Graves' disease

Forty one globulin preparations from patients with Graves' disease were tested for their specific TSH binding properties and compared with their TSI activity in: 1. human thyroid membrane competition assay; 2. adenylate cyclase stimulation; 3. colloid droplet formation. The preparations tested were divided into two well distinguishable groups according to their specific TSH binding: 25 samples out of 41 contained thyrotropin binding sites similar to the globulins from normal healthy persons (A-type binding, Kd: 1.2 pmol-1 g and Bmax: 0.8 pmol g-1) and 17 samples bound TSH with lower affinity but higher capacity (B-type binding mean Kd: 15.3 pmol-1 g, mean Bmax: 2.7 pmol g-1). both A- and B-type TSH binding globulins containing samples were active in binding to human thyroid membrane, in droplet formation and adenylate cyclase stimulation. However, there was a linear correlation between the potential THS binding capacity of a B-type sample and the percentage adenylate cyclase stimulation and droplet formation, whereas the reverse correlation was found with their thyroid membrane binding activity. It was concluded that B-type TSH binding globulins may play a role in the formation and/or modification of the pathogenetic TSH action.