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.

Thyroid-stimulating antibody (TSAb) and TSH binding inhibitor immunoglobulin (TBII) were measured serially in 10 patients with Graves' disease at the time of postpartum onset (n = 2) or relapse (n = 8) of Graves' thyrotoxicosis and in 5 patients with Graves' disease who were in remission and had no postpartum relapse of Graves' thyrotoxicosis. TSAb was measured by a sensitive cAMP accumulation assay using FRTL-5 cells, and TBII was determined by radioreceptor assay. In no patient with either recurrent or new onset postpartum hyperthyroidism did the serum free T3 index (FT3I) rise before the free T4 index (FT4I). Of the 10 patients who had postpartum thyrotoxicosis, concomitant increases in serum FT4I and FT3I, and TSAb and TBII were observed in only 1 patient. Increases in TSAb and TBII after those in FT4I and FT3I occurred in 6 patients. In 1 patient, an increase in TBII was associated with the occurrence of thyrotoxicosis, but TSAb increased 1 month later. In the other 2 patients, a TSAb increase was followed by the development of thyrotoxicosis, but TBII increased later. In 3 of these 10 patients, the increased serum FT4I and FT3I values decreased spontaneously, whereas the TSAb and TBII levels increased continuously. No positive test or increase in TSAb or TBII was found in the 5 patients with Graves' disease who did not have a postpartum relapse of thyrotoxicosis. These data indicate that postpartum initiation of Graves' thyrotoxicosis is not always associated with an increase in circulating anti-TSH receptor antibodies and that such parameters are poor indicators of thyroid function. Intrathyroidal humoral or cell-mediated immunological mechanisms may also be involved in mediating thyrotoxicosis in Graves' disease.

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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