Changes in lymphocyte subsets in whole blood of normal pregnant and postpartum women were examined by flow cytometry with an automated leukocyte differential system. From the first trimester and throughout pregnancy, the absolute counts of T(CD3) and B(CD20) and T-cell subsets (CD4, CD8) decreased with a decrease in the absolute lymphocyte count, although the proportions of these cells remained unchanged except for a decrease in the percentage of T helper-inducer (CD4) cells in the first trimester. On the contrary, the percentage of NK/K (Leu 7) cells, but not of NK/K (CD16) cells, increased in the first trimester and then both gradually decreased in the second and third trimesters. In the postpartum period, the percentages and absolute counts of T(CD3) and NK/K (Leu 7) cells, but not of other cells, increased transiently. These changes of lymphocyte subsets may indicate suppression of immunological activity during pregnancy and its "increase" in the postpartum period.

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.

The universal predictive criteria for neonatal overt thyrotoxicosis requiring treatment were examined in 108 neonates (including a pair of twins) born to mothers with Graves' disease (36 patients under treatment with antithyroid drugs [group A] and 71 in remission [group B]). Anti-thyroid-stimulating hormone (TSH) receptor antibody activity was measured by both radioreceptor assay (TSH-binding inhibitor immunoglobulin [TBII]) and biologic stimulation assay (thyroid stimulating antibody [TSAb]). For generalization of the predictive criteria, the expression of TBII activity was standardized using standard serum made taking units of Medical Research Council long-acting thyroid stimulator, standard B as a reference, and expression of TSAb activity was standardized using bovine TSH as a standard. TBII activity was positive in 22 mothers at delivery, and TSAb activity was positive in 18. In 12 cases, both activities were positive. Both the TBII and the TSAb activity of maternal serum at delivery correlated well with that of the cord serum. Neonatal thyrotoxicosis occurred in 9 of 108 neonates (8%), of whom five (5%) had clinical overt symptoms requiring antithyroid drug treatment. In all nine cases the TBII and TSAb activities were both positive, but no neonate without TBII or TSAb activity developed thyrotoxicosis. The prediction rate (42%) of neonatal overt thyrotoxicosis was higher when both TBII and TSAb were measured than when only TBII (23%) or TSAb (28%) was measured. Clinical overt thyrotoxicosis could be predicted in five of six neonates (83%) of mothers when the cutoff levels of antibody activities were increased to a TBII activity of above 8 U/ml and TSAb activity of above 1.0 TSH microUEq.(ABSTRACT TRUNCATED AT 250 WORDS)

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