Early changes of thyroid hormone concentrations after (131)I therapy in Graves' patients pretreated or not with methimazole

AIM

Despite extensive use of (131)I therapy for Graves' hyperthyroidism the treatment regimen with (131)I and antithyroid drugs remain under discussion. In our prospective clinical study we followed acute thyroid hormone changes after (131)I in patients not pretreated with methimazole (MMI) and in patients with different MMI pretreatment regimens.

PATIENTS, METHODS

187 patients were treated with fixed activity of 550 or 740 MBq of (131)I. First group (71 patients) received (131)I alone. In the second group (57 patients) MMI was stopped seven days before (131)I. The third group (59 patients) received MMI until (131)I application. Initial free triiodothyronin and free thyroxin were measured in the second group 7 and 2 days before (131)I therapy and in all three groups on the day of (131)I application as well as 2, 5, 12, and 30 days afterwards. Absorbed dose was measured in each patient.

RESULTS

In the non-pretreated group (131)I application was followed by a significant decrease of fT4 in 5 days and of fT3 in 2 days, higher reduction was detected in patients with higher baseline values. In MMI pretreated patients significant but clinically irrelevant increase of both thyroid hormones was detected with maximum value 7 days after discontinuation in the second group and 5 days after discontinuation in the third group. Additionally, in patients of the third group absorbed dose of (131)I was significantly lower relative to other two groups. We found no correlation between absorbed dose of (131)I and thyroid hormone changes.

CONCLUSION

Our study demonstrates that (131)I application alone does not result in exacerbation of hyperthyroidism and therefore it may be considered as safe. Additionally, MMI withdrawal causes significant but clinically irrelevant elevation of thyroid hormones.

Early change of thyroid hormone concentration after 131I treatment in patients with solitary toxic adenoma

AIM

In spite of extensive use of 131I for treatment of hyperthyroidism, the results of early outcome are variable. In our prospective clinical study we tested whether 131I induced necrosis causing clinical aggravation of hyperthyroidism and increasing the free thyroid hormone concentration in the serum of patients with solitary toxic adenoma not pretreated with antithyroid drugs.

PATIENTS AND METHODS

30 consecutive patients were treated with 925 MBq 131I. Serum concentration of thyrotropin (TSH), free thyroxine (fT4), free triiodothyronine (fT3), thyroglobulin (Tg), and interleukin-6 (IL-6) were measured before and after application of 131I.

RESULTS

After application of 131I no clinical worsening was observed. FT4 and fT3 concentration did not change significantly within the first five days, whereas both of them significantly decreased after 12 days (p < 0.0001). Slight and clinically irrelevant increase in the level of the two thyroid hormones was observed in 9 patients. Furthermore, we observed a prolonged increase in Tg concentration and a transient increase in IL-6 concentration.

CONCLUSION

Neither evidence of any clinical aggravation of hyperthyroidism nor any significant increase in thyroid hormone concentration by 131I induced necrosis of thyroid cells was found. Therefore, the application of 131I may be considered as a safe and effective treatment for patients with hyperthyroidism due to toxic adenoma.

The influence of the exon 1 polymorphism of the cytotoxic T lymphocyte antigen 4 gene on thyroid antibody production in patients with newly diagnosed Graves' disease

Increasing evidence supports the genetic susceptibility for thyroid antibody (TAb) production in patients with autoimmune thyroid disease, and recently, it has been shown that the cytotoxic T lymphocyte antigen 4 (CTLA-4) gene is most likely a major TAb susceptibility gene. To assess the relationship between exon 1 CTLA-4 gene polymorphism and TAb production, we genotyped 67 patients with newly diagnosed Graves' disease. Free thyroid hormones and TAb were measured, including thyroglobulin antibodies (TgAb), thyroid peroxidase antibodies (TPOAb), and thyroid-stimulating antibodies (TSAb). AA genotype was found in 25 patients, AG genotype in 34 patients, and GG genotype in 8 patients. G allele carrying genotypes showed significantly higher frequency of positive TPOAb (p < 0.005) and TgAb (p < 0.05) compared to AA genotype. Furthermore, the median values of TPOAb were significantly higher in the group with G allele (p < 0.002). However, the median values of TgAb and TSAb did not differ significantly between both groups and similarly, CTLA-4 genotype showed no association with serum free thyroxine (T(4)) and Graves' ophthalmopathy. In conclusion, our findings suggest that G allele carrying genotype of the CTLA-4 gene influences higher production of TPOAb and TgAb, and therefore, support the hypothesis that CTLA-4 gene plays a major role in TAb production.