Protein-chemical standardization of the erythrocyte glutathione reductase activation test (EGRAC test). Application to hypothyroidism.

The erythrocyte glutathione reductase activation coefficient (EGRAC) is an index of riboflavin deficiency or, more exactly, of FAD deficiency in man. In this report a sensitive version of the EGRAC test is introduced that is based on the molecular properties of glutathione reductase and its FAD-free apoenzyme. The hemoglobin concentration of the blood sample can be estimated simultaneously using the spectrophotometric absorption at 340 nm. - The method was tested for 33 thyroidectomized patients in comparison with a euthyroid control group. From the average EGRAC values (1.40 vs. 1.22) it was deduced that the average free FAD level was approximately 2 times lower for the patients' than for the control group. Discussed is the role of the EGRAC test in hormonal and nutritional disorders.