Free radicals and Graves' disease: the effects of therapy.

Plasma thiol (PSH), caeruloplasmin (CP), intracellular lysate thiol (LSH) and superoxide dismutase (SOD) activity were measured in 30 patients with newly diagnosed Graves' disease (GD). Compared to control subjects (C) PSH and SOD were significantly reduced (C vs GD, 507 vs 449 mumol/l, P less than 0.01; 2.1 vs 1.6 mumol/l, P less than 0.01 respectively) and LSH was significantly raised (C vs GD 181 vs 298 mumol/l). Treatment with carbimazole produced a significant rise in LSH and SOD. Propylthiouracil (PTU) treatment raised LSH levels but 131I treatment produced no significant change. All four parameters are involved in different ways in oxygen metabolism and together provide an indication of oxidative stress across the red-cell membrane. In addition LSH is a general radical scavenger and SOD a specific O2- scavenger. In Graves' disease the increased oxidative stress and increased general radical scavenging may result from raised free-radical activity. These changes, which have not previously been reported in Graves' patients, were modified by antithyroid drug therapy, but it is not clear whether this is a direct or indirect effect.