Development of primary hypothyroidism with the appearance of blocking-type antibody to thyrotropin receptor in Graves' disease in late pregnancy

Incidence of Neonatal Hyperthyroidism Among Newborns of Graves' Disease Patients Treated with Radioiodine Therapy

BACKGROUND

The serum thyrotropin receptor antibody (TRAb) titers of Graves' disease (GD) patients are known to increase after radioiodine (RAI) therapy, and they can remain high for years. The incidence of neonatal hyperthyroidism (NH) among newborns of mothers with GD who conceived after RAI therapy has not been previously reported. The aims of this study were to investigate the incidence of NH among newborns of mothers who conceived within two years after RAI therapy, and to identify predictors of NH.

METHODS

GD patients (n = 145) who conceived within two years after RAI therapy were retrospectively reviewed, and information regarding their newborns was collected.

RESULTS

Of the 145 pregnant women, 54 (37%) were treated with antithyroid drugs or potassium iodide for maternal hyperthyroidism during the first trimester. There were eight newborns with NH, resulting in an incidence of 5.5%. Seven of the eight mothers whose newborns had NH were treated with antithyroid drugs or potassium iodide during their pregnancy. The incidence of NH among the newborns of mothers who conceived within 6-12 months after RAI therapy was 8.8%, within 12-18 months was 5.5%, and within 18-24 months was 3.6%. Multivariate analysis revealed that the TRAb values in the third trimester were the only risk factor for NH. The cutoff TRAb value in the third trimester for predicting NH was 9.7 IU/L (reference value <2.0 IU/L).

CONCLUSIONS

The incidence of NH among newborns of mothers who conceived within two years after RAI therapy was 5.5%. The fetuses of pregnant GD patients whose TRAb value is high in the third trimester should be carefully followed by an obstetrician during pregnancy, and the newborns should be carefully followed by a pediatrician after birth.

Hyperthyroidism During Pregnancy: Etiology, Diagnosis and Management

Pregnancy has marked effects on thyroid physiology and autoimmune thyroid disease tends to ameliorate through gestation due to the general immunosuppression seen in pregnancy. There is a need for trimester-specific thyroid hormone reference ranges. Hyperthyroidism in pregnancy – usually due to Graves' disease – is not common but, if the patient is compliant, a good outcome can be expected for both mother and child if treatment with anti-thyroid drugs (propylthiouracil is preferred) is instituted. Thyroid-stimulating hormone receptor antibody should be measured at 36 weeks in such patients in order to predict the possibility of neonatal hyperthyroidism. Transient gestational hyperthyroidism is often associated with hyperemesis gravidarum and thyroid function should be checked in patients severely affected by this condition. Radioiodine therapy is contraindicated in pregnancy but thyroid surgery may be performed safely in the second trimester. Autoimmune thyroiditis and Graves’ hyperthyroidism occur quite commonly in postpartum women.

High cut-off value of a chimeric TSH receptor (Mc4)-based bioassay may improve prediction of relapse in Graves' disease for 12 months

There are scarce reports regarding a functional prognostic value of thyroid-stimulating autoantibody (TSAb) levels using a thyroid-stimulating hormone receptor chimera (Mc4) in Graves' disease (GD) in iodine sufficient area. The aim of this study was to investigate whether Mc4-TSAb can predict GD remission/relapse after antithyroid drug (ATD) treatment and to compare Mc4-TSAb with a binding assay using M22 monoclonal antibody (M22-TRAb) in GD patients. We retrospectively reviewed the results of M22-TRAb and Mc4-TSAb in GD patients treated with ATD for 12 months. GD patients who underwent ATD treatment for at least 12 months were included. We compared the predictive values of M22-TRAb and Mc4-TSAb for GD remission and relapse. Of the 92 patients, 60 (65.2%) achieved remission and 32 (34.8%) relapsed within 12 months. In receiver operating characteristic analysis, there were no significant differences in the area under the curves (AUCs) between Mc4-TSAb [AUC=0.79 (95% CI 0.69-0.89)] and M22-TRAb [AUC=0.69 (95% CI 0.58-0.81)]. The optimal predictive cut-off values of M22-TRAb and Mc4-TSAb were 2.23 IU/L and 230%, respectively. At a high Mc4-TSAb cut-off, the better specificity of 85.0% and positive predictive value (PPV) of 69.0% were shown compared with those at the best cut-off for M22-TRAb. In conclusion, a high cut-off for an Mc4 assay may improve the predictive value of relapse with superior specificity and PPV compared with M22-TRAb in treated GD.

Hyperthyroidism during pregnancy: etiology, diagnosis and management

Pregnancy has marked effects on thyroid physiology and autoimmune thyroid disease tends to ameliorate through gestation due to the general immunosuppression seen in pregnancy. There is a need for trimester-specific thyroid hormone reference ranges. Hyperthyroidism in pregnancy - usually due to Graves' disease - is not common but, if the patient is compliant, a good outcome can be expected for both mother and child if treatment with anti-thyroid drugs (propylthiouracil is preferred) is instituted. Thyroid-stimulating hormone receptor antibody should be measured at 36 weeks in such patients in order to predict the possibility of neonatal hyperthyroidism. Transient gestational hyperthyroidism is often associated with hyperemesis gravidarum and thyroid function should be checked in patients severely affected by this condition. Radioiodine therapy is contraindicated in pregnancy but thyroid surgery may be performed safely in the second trimester. Autoimmune thyroiditis and Graves' hyperthyroidism occur quite commonly in postpartum women.

Screening for thyroid dysfunction in pregnancy: is it worthwhile?

There is a high incidence of thyroid dysfunction during pregnancy resulting in adverse maternal (miscarriages, anaemia in pregnancy, preeclampsia, abruptio placenta and post-partum haemorrhage) and fetal effects (premature birth, low birth weight, increased neonatal respiratory distress) which may justify screening for thyroid function during early pregnancy with interventional levothyroxine therapy for thyroid hypofunction. There is a greater prevalence of subclinical hypothyroidism in women with delivery before 32 weeks and there is even an association between thyroid autoimmunity and adverse obstetric outcome, which is independent of thyroid function. Higher maternal TSH levels even within the normal reference range are associated with an increased risk of miscarriages, fetal and neonatal distress and preterm delivery. There are few prospective randomised trials to substantiate the benefit of screening and the recently reported CATS study did not show a benefit in child IQ at age 3 years. Nevertheless there seems to be a case for screening to prevent adverse obstetric outcomes. The clinical epidemiological evidence base does not justify universal screening at the present time. However, it is probable that more evidence will be produced which may alter this view in the future.

Management of Graves' hyperthyroidism in pregnancy: focus on both maternal and foetal thyroid function, and caution against surgical thyroidectomy in pregnancy

Graves' disease is a common autoimmune disorder in women in fertile ages. The hyperthyroidism is caused by generation of TSH-receptor activating antibodies. In pregnancy both the antibodies and the antithyroid medication given to the mother pass the placenta and affect the foetal thyroid gland. Thyroid function should be controlled not only in the mother with Graves' hyperthyroidism but also in her foetus.The review includes two cases illustrating some of the problems in managing Graves' disease in pregnancy. Major threats to optimal foetal thyroid function are inadequate or over aggressive antithyroid drug therapy of the mother. It should be taken into account that antithyroid drugs tend to block the foetal thyroid function more effectively than the maternal thyroid function, and that levothyroxin (L-T(4)) given to the mother will have only a limited effect in the foetus. Surgical thyroidectomy of patients with Graves' hyperthyroidism does not lead to immediate remission of the autoimmune abnormality, and the combination thyroidectomy+withdrawal of antithyroid medication+L-T(4) replacement of the mother involves a high risk of foetal hyperthyroidism. Conclusion Antithyroid drug therapy of pregnant women with Graves' hyperthyroidism should be balanced to control both maternal and foetal thyroid function. Surgical thyroidectomy of a pregnant woman with active disease may lead to isolated foetal hyperthyroidism.

Spontaneous Hypothyroidism in the Follow up of Graves Hyperthyroid Patients Treated with Antithyroid Drugs

AIM

Spontaneous hypothyroidism may follow the natural course of Graves disease (GD) after treatment with antithyroid drugs (ATD).

METHODS

We studied retrospectively 139 remitted Graves hyperthyroid patients treated with ATD, with a follow-up period of 17.5 years (range 6 to 25 years). Elevated serum concentration of thyroid-stimulating hormone and low serum thyroxine concentrations confirmed the diagnosis.

RESULTS

Thirteen patients (median age, 41 years; 26 to 48 years) developed spontaneous hypothyroidism, 4 to 144 months (median, 48 months ) following withdrawal of ATD. The prevalence of hypothyroidism was 9.3% and the incidence was 2.3% per year (13/ 563.6 patients/year of observation). There was no association with types of drugs used or the regimens. Spontaneous hypothyroid patients showed elevated titers (P = 0.02) of serum antithyroid peroxidase antibody (TPOAb) at the end of treatment with ATD, compared with the titers found at the beginning. These patients also had higher titers of TPOAb (P = 0.01) in relation to euthyroid patients. In contrast, the changes in serum antithyroglobulin antibody titers were not significant.

CONCLUSIONS

Because of the shift from euthyroidism to spontaneous hypothyroidism, GD patients demanded a strict follow up after ATD therapy. It seems that there is an effect of TPOAb on thyroid destruction.

One Case of Fetal and Neonatal Variable Thyroid Dysfunction in the Context of Graves’ Disease

Cases of maternal thyroid dysfunction are not always clearly identified during pregnancy. We report here the case of a 36-year-old patient with a history of treated Graves' disease whose child successively presented with a hypo- and hyperthyroid dysfunction that was difficult to treat despite the administration of synthetic antithyroid drugs and beta-blockers. The patient's thyroid hormone levels were normal during pregnancy, while still secreting anti-TSH-receptor autoantibodies. With time, these antibodies went from an inhibiting to a stimulating activity. Fetal monitoring using only ultrasonography had been proposed to the patient. With such a follow-up associated with fetal blood sampling it would have been possible to treat already in utero the thyroid dysfunction. The management of such patients is not limited to the follow-up of the maternal thyroid hormones, but should also evaluate the activity of the anti-TSH-receptor autoantibodies around the 28th week of amenorrhea and their effect on fetal blood. Fetal and neonatal thyroid dysfunctions have a major impact, but they can be detected and treated in utero. The clinical, laboratory and ultrasound follow-up makes it possible to monitor patients who are at risk and to propose a therapeutic and obstetrical management.

A luminescent bioassay for thyroid blocking antibodies

OBJECTIVE

Thyroid blocking antibodies (TBAb) have a role in the development of hypothyroidism and in the neonate are responsible for transient hypothyroidism. Specific measurement of TBAb requires a bioassay, but current methods are lengthy and cumbersome. We describe a rapid luciferase-based method for the detection of TBAb using the lulu* cell line which is suitable for the provision of a clinical service

PATIENTS AND MEASUREMENTS

Chinese hamster ovary (CHO) cells were transfected with human TSH-R together with G418 resistance and a cAMP responsive luciferase construct. Stable pools of transfected cells were selected and clones identified by limiting dilution. Clone lulu* gave the best response to stimulation by TSH and was used to develop a bioassay for TBAb. The luminescent bioassay conditions have been optimized and validated using 12 serum samples from patients found to be TBAb positive in a bioassay using an established method quantifying cAMP by radioimmunoassay (RIA). The effect of thyroid stimulating antibodies (TSAb) on the calculation of Inhibition Index (InI) using two previously described formulae have been investigated and we have used serum containing both TSAb and TBAb to investigate detection of TBAb in samples containing more than one type of activity.

RESULTS

Lulu* displays a dose dependent increase in luciferase expression in response to stimulation with bovine (b) TSH which is more effective in serum free medium than in salt free buffer. TSH stimulated luciferase expression can be inhibited by TBAb in either serum or an immunoglobulin preparation. Using optimized assay conditions, challenging 10% serum against 1 U/l bTSH in culture medium, we have tested 31 euthyroid sera to determine a reference range: InI values >23% were considered positive. Twelve samples previously shown to contain TBAb by an established method quantifying cAMP by RIA were positive by the luciferase-based assay. Of control sera, 20/20 systemic lupus erythematosus, 13/14 rheumatoid arthritis, 12/12 multinodular goitre were negative. We demonstrated that if more complex formulae are used to calculate InI, false positive TBAb results can be obtained in samples containing only TSAb. Finally, when sera contain both TSAb and TBAb, the net activity of stimulating and blocking antibodies is detected in the bioassay. Where TSAb are also present, analysis of serum may be required at several dilutions to detect TBAb.

CONCLUSIONS

We describe the production of a new cell line, lulu*, and its use to develop a luminescent bioassay for TBAb suitable for clinical use. Comparing two established methods of calculating TBAb, we found that they do not give identical results. In light of this, the high prevalence reported for TBAb in some studies has to be considered with caution.

Thyroid disease in relation to pregnancy: a decade of change

Inspection of the references cited in this review indicates that much work has occurred in the area of thyroid and pregnancy during the last decade. Significant advances in our understanding of the immunology of pregnancy and the effect of thyroid disease on this process have taken place. The role of hCG in the physiology of pregnancy and its relevance to thyroid function has been an emerging theme. There is still no clear explanation for the association between thyroid antibodies and infertility or miscarriage. During the last decade a general concensus has developed in relation to the management of hyperthyroidism in pregnancy although there are still variations in antithyroid drug use at this time. The aetiological classification of congenital hyper- and hypothyroidism utilizing new technologies has opened up a new perspective on these disorders. Attention has been drawn to the importance of treating maternal hypothyroidism with adequate thyroid replacement therapy and to the possibility of impaired child neuropsychological development consequent on low maternal thyroid hormone concentration in early gestation in non iodine deficient areas. Significant advances have been made during the last decade in the description of the clinical features and in our understanding of the pathogenesis of postpartum thyroid disease. The importance of long-term follow up of selected patient groups has also been emphasized.