Evidence of a correlation between thyrotrophin receptor binding inhibition and thyroid adenylate cyclase activation by immunoglobulins in Graves' disease before and during long-term antithyroid treatment

Abstract

Abstract. In the present study we have measured in parallel thyrotrophin binding inhibiting immunoglobulins (TBII) and thyroid adenylate cyclase stimulating immunoglobulins (TACSI) in patients with Graves' disease (GD) both before and during long-term antithyroid treatment. A statistical model based on the calculation of the differences (TACSI-TBII) is presented, comparing the changes in this parameter to the analytical variation. The correlation between TBII and TACSI in 52 patients with GD before treatment was: r = 0.58, P < 0.0001. During long-term antithyroid treatment of GD the 2 activities changed in parallel in 39 of 45 patients followed. In a few patients discrepancies were observed, and 1 patient, initially TACSI positive, developed adenylate cyclase inhibiting IgG during treatment but without detectable TBII. In conclusion, 1) TBII and TACSI are significantly correlated in patients with GD both before and during long-term antithyroid treatment, 2) in some patients discrepancies between TBII and TACSI suggest, that these IgGs are heterogeneous with varying capacity for stimulation of the adenylate cyclase and receptor binding, and 3) adenylate cyclase inhibitory IgG without TBII activity was demonstrated in GD.