Kinetic analyses of changes in serum TSH receptor antibody values after total thyroidectomy in patients with Graves' disease

We often recommend total thyroidectomy for patients with Graves' disease who wish to have a child in the near future in order to prevent fetal or neonatal hyperthyroidism, especially if the patients' serum thyrotropin receptor antibody (TRAb) values are high. The aim of this study was to analyze changes in serum TRAb values using a quantitative third generation assay after total thyroidectomy and the half-lives of serum TRAb values to estimate the postoperative time needed to achieve the safe TRAb value for mothers. We retrospectively examined the records of 45 Graves' disease patients who underwent a total thyroidectomy and had high serum TRAb values. We also evaluated factors that prolonged the postoperative reduction of serum TRAb values. The serum TRAb values decreased rapidly in most of the patients, especially within the early postoperative (3-month) period. The presence of Graves' ophthalmopathy (GO) (p=0.001), smoking (p=0.004), and serum thyroglobulin values > 0.5 ng/mL at postoperative 12 months (p=0.039) were significantly associated with prolonged half-lives of the serum TRAb values. The median TRAb value half-life was 93.5 days in the patients without GO or smoking, 162.5 days in the patients with GO or smoking, and 357.4 days in the patients with both GO and smoking. Our findings indicate that using the half-life of patients' serum TRAb values determined by this third generation assay would be effective to evaluate the reduction of serum TRAb values after total thyroidectomy and to estimate the postoperative time needed to achieve the maternal safe value.