Differential Diagnostic Value of TSH Receptor Antibody Measurements in Thyrotoxic Postpartum Patients with History of Graves' Disease / 대한내분비학회지

ABSTRACT

BACKGROUND: It is known that pregnancy markedly influences the clinical course of autoimmune thyroid diseases. In the postpartum period, various kinds of autoimmune thyroid dysfunctions can be observed. Thyroid dysfunction is found in 5.5-7.1% of postpartum women in the general population. Among those who show thyroid dysfunction after delivery, some will develop Graves' disease and others will develop postpartum thyroiditis. It is also known that patients with Graves' disease may manifest thyrotoxicosis in the postpartum period because of postpartum thyroiditis or relapse of the Graves' disease itself. We evaluated the clinical features of postpartum thyrotoxicosis in Graves' disease patients to find diagnostic indices that could be used in differentiating between postpartum thyroiditis and relapse of Graves' disease. METHOD: We reviewed the cases with postpartum thyrotoxicosis in patients that had a history of Graves' disease between 1995 and 2000. The diagnosis of postpartum thyroiditis had been made by means of a 99mTc thyroid scan or by the observation of a typical triphasic thyroid function change, in cases where a 99mTc thyroid scan was not possible because of breast feeding. We measured the serum TSH, free T4, free T3, TSH binding inhibiting immunoglobulin (TBII), anti-thyroid peroxidase (TPO) antibody, and anti- thyroglobulin (Tg) antibody serially from the time of the diagnosis of Graves' disease to the time of postpartum thyroid dysfunction. RESULTS: Eleven patients, 5 patients in the postpartum thyroiditis (PPT group) and 6 patients with relapse of the Graves' disease (GD group), were identified. The mean values of TBII of two groups at the time of diagnosis of Graves' disease were 40.9+/-4.8 IU/mL (PPT group), 58.9+/-23.5 IU/mL (GD group) respectively, which were insignificant. The mean values of TBII of the two groups at early pregnancy were 3.2+/-1.9 IU/mL (PPT group), 41.6+/-22.6 IU/mL (GD group) and this difference was statistically significant (p=0.009). The mean values of TBII of the two groups at the time of postpartum thyrotoxicosis were 1.9+/-1.6 IU/mL (PPT group), 51.5+/-23.2 IU/mL (GD group) which were also statistically significant (p=0.003). The mean values of anti-TPO antibody, anti-Tg antibody, disease duration, and treatment duration between the two groups were not significantly different. The onsets of thyroid dysfunction after delivery in the two groups were 2.6+/-2.0 (PPT group), 4.0+/-3.9 (GD group) months which were statistically insignificant. CONCLUSION: These data suggest that the measurement of TBII at the time of the postpartum thyrotoxic period, could help to differentiate postpartum thyroiditis from a relapse of Graves' disease in those patients that have a history of Graves' disease especially when thyroid scan is not possible because of breast feeding.