The effect of double filtration plasmapheresis on thyroid hormone economy and thyroid function.

Five cases of rheumatoid arthritis (RA), two cases of systemic lupus erythematosus (SLE), a case of mixed connective tissue disease (MCTD), and a case of cold urticaria were treated with double filtration plasmapheresis (DFP). Each aliquot of plasma was obtained at three different points of the DEP circuit during the treatment and concentrations of thyroid hormones as well as thyroxine binding globulin (TBG) were measured. Despite the removal of considerable amounts of triiodothyronine (T3), thyroxine (T4), and TBG from the plasma, levels of plasma free T3 (FT3) and free T4 (FT4) before and immediately after DFP treatment were not significantly different. These results indicate that DEP therapy rarely affects plasma concentration of active thyroid hormones in patients who undergo such therapy.