A baby with congenital hypothyroidism born to a hypothyroid mother who expressed undiagnosed thyroid stimulation blocking antibody

In adults, hypothyroidism caused by thyroid stimulation blocking antibody (TSB Ab) is rare, and confirmed cases are even fewer, as TSB Ab levels are rarely assayed. However, this may create problems in babies, as the transplacental passage of maternal TSB Ab can cause a rare type of hypothyroidism in the infant. Prompt levothyroxine replacement for the baby starting immediately after birth is important. We describe a congenital hypothyroid baby born to a hypothyroid mother who was not aware of the cause of her hypothyroid condition, which turned out to be associated with the expression of TSB Ab. This cause was confirmed in both the infant and mother using a series of thyroid function tests and measurements of autoantibody levels, including TSB Ab. During periodic follow-up, the TSB Ab and thyroid stimulating hormone receptor antibody titers became negative in the baby at 8 months of age, but remained positive in the mother. Evaluation of hypothyroidism and its cause in mothers during pregnancy is important for both maternal and child health.

A baby with congenital hypothyroidism born to a hypothyroid mother who expressed undiagnosed thyroid stimulation blocking antibody

In adults, hypothyroidism caused by thyroid stimulation blocking antibody (TSB Ab) is rare, and confirmed cases are even fewer, as TSB Ab levels are rarely assayed. However, this may create problems in babies, as the transplacental passage of maternal TSB Ab can cause a rare type of hypothyroidism in the infant. Prompt levothyroxine replacement for the baby starting immediately after birth is important. We describe a congenital hypothyroid baby born to a hypothyroid mother who was not aware of the cause of her hypothyroid condition, which turned out to be associated with the expression of TSB Ab. This cause was confirmed in both the infant and mother using a series of thyroid function tests and measurements of autoantibody levels, including TSB Ab. During periodic follow-up, the TSB Ab and thyroid stimulating hormone receptor antibody titers became negative in the baby at 8 months of age, but remained positive in the mother. Evaluation of hypothyroidism and its cause in mothers during pregnancy is important for both maternal and child health.

Measurements of Thyroid Stimulation Blocking Antibody Activities by Chinese Hamster Ovary ( CHO ) cells Expressing Human TSH Receptors in Patients with Primary Hypothyroidism / 대한내분비학회지

BACKGROUND: The Chinese hamster ovary cells transfected with human TSH receptor cDNA (hTSHR-CHO), expressing functional human TSH receptors, are known to be more sensitive in detection of thyroid stimulating antibodies than FRTL-5 cells. There has been no report on the usefulness of these cells to measure thyroid stimulation blocking antibody (TSBAb) activity which is frequently found in patients with primary myxedema, METHODS: We established the optimal assay condition of measurement of TSBAb using hTSHR-CHO cells, and simultaneously measured TSBAb activities with FRTL-5 cells and with hTSHR-CHO cells in 49 patients with primary myxedema, compared them with their thyrotropin binding inhibitor immunoglobulin (TBII) activities. RESULTS: 1) hTSHR-CHO cells specifically bound bTSH and were stimulated by bTSH in terms of cyclic AMP generation in a dose dependent manner. 2) Myxedema IgG suppressed TSH-stimulated cAMP production of hTSHR-CHO cells in a dose dependent manner reaching plateau at the concentration of I g/L. Normal pooled IgG has no suppressive action at the concentration of less than 1 g/L, but caused significant suppression at the concentration of greater than 1g/L. 3) TSBAb activities measured by hTSHR-CHO cells in 49 patients with primary myxedema were as follows: Four of 25 TBII-negative cases (16%) and 22 of 24 TBII-positive cases (92%) had TSBAb activities. Most of TSBAb positive patients (95%), especially in TBII positive cases, showed very high activities of more than 90%. 4) TSBAb activities measured by hTSHR-CHO cells and those by FRTL-5 cells were both positive in 24 patients (49%), both negative in 18 patients (37%), and were discrepant in 7 patients (14%). The TSBAb activities measured with hTSHR-CHO cells and those measured with FRTL-5 cells were significantly correlated (r=0.71, p< 0.01). 5) Forty five percent of patients with primary myxedema had all of 3 kinds of activities (TBII, hTSHR-CHO cell TSBAb, FRTL-5 cell TSBAb), 37% of them had none of 3 activities and 18% of them had 1 or 2 kinds of activities only. CONCLUSION: The usefulness of hTSHR-CHO cells in measurements of TSBAb activities were confirmed. The TSBAb activities of most patients with primary myxedema measured by hTSHR-CHO cells were concordant with those measured by FRTL-5 cells. However, a small subset of patients (18%) had discrepant results in assays of TSH receptor antibodies according to the differences in TSH receptors (rat, human and porcine) used in assay. Such discrepancy may be explained by heterogeneity in epitopes for blocking TSH receptor antibodies.

Clinical Significance and Immunological Characteristics of Blocking TSH Receptor Antibodies in Patients with Hashimoto's Thyroiditis / 대한내분비학회지

BACKGROUND: TSH receptor blocking antibody (TRBAb) is a pathogenic factor in the vast majority of patients with primary myxedema. It has been reported that TRBAbs are found in some patients with chronic goitrous autoimmune thyroiditis (Hashimoto's thyroiditis), but the significance or the role of TRBAb in Hashimotos thyroiditis is not clear, We recently reported that hTSHR-CHO cells which express the functional human TSH receptors are more sensitive and are better in detecting functional TSH receptor antibodies in Graves patients than FRTL-5 cells. We are to investigate the biological role of TRBAb in Hashimotos thyroiditis by measuring thyroid stimulation blocking antibody (TSBAb) activities of Hashimoto's IgG's using hTSHR-CHO cells. Moreover, we are to see if there is any difference in epitope recognition between Hashimotos TRBAb and myxedema's TRBAb by measuring TSBAb activities with mutant receptor expressing cell lines, Mcl+2 and Mc 2 in those patients. METHOD: We measured TSBAb activities of IgGs from patients with primary myxedema (PM, n= 10) and those with hypothyroid (n 20) or euthyroid (n 17) Hashimoto's thyroiditis (HT) using wild type hTSHR-CHO cells (WT) and two chimeric receptor expressing cell lines, Mcl+2 and Mc2. RESULTS: TSBAb activities measured by WT were higher in hypothyroid HT than in euthyroid HT (30.0+-23.2% vs. 6.1+-28.7, p<0.05), and TSBAb-positive rate tend to be higher in the former (20%, 5/20) than in the latter (0%, 0/17, p=0.07). TRBAbs from PM (n=4) had high TBII activities and had persistent blocking activities despite of the replacement of amino acid residue 8~165 of extracellular domain of TSHR with those of rat LH/CGR (Mcl +2). However, TRBAbs from HT (n=4) had no TBII activity at all and lost blocking activities when measured with Mcl+2. CONCLUSION: TRBAbs are found in 20% of hypothyroid patients with Hashimotos thyroiditis in assay using hTSHR-CHO cells, and they seem to play a role in the development of hypothyroidism in some patients with Hashimotos thyroiditis. TRBAbs of Hashimotos thyroiditis are different in epitope recognition from TRBAbs of primary myxedema.

Changes in Properties of Thyrotropin Receptor Antibodies Following Radioiodine Treatment in Patients with Graves' Disease / 대한내분비학회지

BACKGROUND: It has been suggested that thyroid stimulation blocking antibody (TSBAb) is involved in the development of early hypothyroidism after radioiodine treatment in patient with Graves disease. However, previous studies have reported the effect of radioiodine treatment on overall changes of TSH receptor antibodies without detailed observation of changes in properties of TSH receptor antibodies. The aim of this study is to evaluate the effect of radioiodine treatment on thyroid stimulation antibody (TSAb) or on thyroid stimulation blocking antibody (TSBAb) activities and to see whether the appearance of TSBAb after radioiodine treatment is involved in the development of early hypothyroidism in patients with Graves disease. METHODS: The activities of TSAb, TSBAb were measured serially with human TSH receptor transfected Chinese hamster ovary (CHO) cells in 36 patients with Graves disease who received 131I treatment. In addition to the wild type TSH receptor-expressing cells, we used a chimeric receptor that 90-165 amino acid residues were substituted by those of rat LH/CG receptor (Mc2) for measurement of TSBAb without interference by the presence of TSAb and for evaluation of TSAb epitope spreading. We evaluated the association of early hypothyroidism after 131I treatment with changes of various immunologic parameters. RESULTS: In 14 (39%) of 36 patients, TSBAb activities were present in their sera before or after 131I treatment. Four of them had TSBAb activities before 131 treatment, and 12 newly acquired TSBAb activities after 131I treatment. The existence of TSBAb was not associated with the development of early hypothyroidism after 131I treatment but with low TSAb activities before 131 treatment, high thyroidal uptake of 131I given and with old age. The phenomena of epitope spreading measured by TSAb with Mc2 mutant clone before and after 131I treatment was not infrequent, but it had no clinical relevance. CONCLUSION: These results suggest that the existence of TSBAb may be not a major factor in the development of early hypothyroidism after radioiodine treatment in Graves disease. Other factors such as TSAb activities before radioiodine treatment, the efficiency of thyroidal uptake of 131I or old age are associated with the development of early hypothyroidism.