ASSOCIATION BETWEEN THYROID MICROSOMAL ANTIBODIES OF SUBCLASS IGG-1 AND HYPOTHYROIDISM IN AUTOIMMUNE POSTPARTUM THYROIDITIS

  • 1 January 1986
    • journal article
    • research article
    • Vol. 63  (1) , 80-86
Abstract
The potential role of thyroid microsomal (Mic) antibodies in the development of postpartum hypothyroidism was investigated in 34 euthyroid women, whose sera were found to contain Mic antibodies in pregnancy. Additional serum samples were obtained 2, 5 and 10-12 months after delivery and analysed for IgG class and IgG subclass levels of Mic antibodies by ELISA techniques. Characteristically, Mic antibodies decreased from early pregnancy to 2 months postpartum, increased two-fold 5 months postpartum and had returned 10-12 months postpartum to the early pregnancy level. Mic antibodies were predominantly subclass IgG-1 or IgG-4 with only minor contributions from IgG-2 and IgG-3. In each individual the percentage contribution made by each IgG subclass to Mic antibody was essentially similar in early pregnancy and the postpartum period despite changes in total IgG class Mic antibody. During the year following delivery, thyrotoxicosis alone (Grave''s disease) developed in 5 women. In the remaining 29 patients the absolute levels of Mic antibodies of IgG-4 subclass were similar 5 months postpartum in women with maximal serum thyrotropin (TSH) > 20 mU/1 (mean optical density in ELISA .+-. s.d.; 0.84 .+-. 0.538; n = 13) and in women with maximal TSH < 10 mU/1 (0.69 .+-. 0.457; n = 16). In contrast, significantly higher values were observed for Mic antibody of IgG-1 subclass in patients with TSH > 20 mU/1 (1.14 .+-. 0.440) compared with women with maximal TSH < 10 mU/1 (0.65 .+-. 0.289) (P < 0.001 by t-test for groups). These results imply that the magnitude of Mic antibody levels of subclass IgG-1 but not IgG-4 is associated with the development of postpartum hypothyroidism and possibly with tissue destructuon in autoimmune thyroid disease in general.