Influence of obstetric factors on the development of postpartum antithyroid antibodies
The long term clinical outcome of postpartum hypothyroidism was investigated by follow-up studies of 44 patients (59 postpartum episodes; mean age of mothers at delivery, 28.2 yr) 5 or more yr later (mean interval after delivery, 8.7 yr; range, 5-16 yr). Forty-nine episodes (83%) in 34 women were followed by recovery within 1 yr postpartum, and those women remained euthyroid thereafter (group A); 10 women [10 episodes (17%)] developed permanent hypothyroidism during the follow-up period (group B). Five women in group B recovered during the first year, but became hypothyroid again later, the other 5 women in Group B remained persistently hypothyroid. HLA typing revealed significantly higher frequencies of HLA-DR3, -DRW8, -DRW9, -A26, -BW46, and -BW67, and significantly lower frequencies of HLA-DR2, -BW52, -BW62, and -CW7 in women with postpartum hypothyroidism than in normal women. Of 9 women with postpartum hypothyroidism who had HLA-DRW9 and/or -B51 associated with antithyroglobulin-antibody titers of 2(3) X 10 or higher, 6 developed permanent hypothyroidism. We conclude that long term follow-up is essential for women of postpartum hypothyroidism because of the risk of permanent hypothyroidism. The results suggest that some immunogenetic factors may be related to the etiology of postpartum hypothyroidism and that women with HLA-DRW9 and/or -B51 and higher titers of antithyroglobulin antibody are likely to develop permanent hypothyroidism.