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Anticlastogenic Effect of Ginkgo Biloba Extract in Graves’ Disease Patients Receiving Radioiodine Therapy

Departments of Internal Medicine (A.D., N.C., F.M.), Biology (M.B., R.B.), and Oncology, Transplants and Advanced Technologies in Medicine (E.L., G.M.), University of Pisa, 67-56126 Pisa, Italy; Department of Morphological-Biomedical Sciences (M.F.), University of Verona, 37134 Verona, Italy; and Health Physics Service (C.T.), S. Chiara Hospital, 56100 Pisa, Italy

Address all correspondence and requests for reprints to: Fabio Monzani, M.D., Department of Internal Medicine, University of Pisa, via Roma 67-56126 Pisa, Italy. E-mail: fmonzani{at}med.unipi.it.

Background: Chromosomal damage, as assessed by clastogenic factors (CFs) and micronuclei (MN) appearance, after radioiodine therapy of Graves’ disease has been reported.

Objective and Methods: Our objective was to evaluate the effect of Ginkgo biloba extract (EGb 761) supplementation on the time course (up to 120 d) of CFs and MN appearance in lymphocytes from patients with Graves’ disease after iodine-131 (¹³¹I) therapy. Patients were randomly assigned to EGb 761 or placebo, in a blinded manner.

Results: In the placebo group, MN increased early (P < 0.001) after ¹³¹I, peaking at the 21st day (P = 0.0003) and declining thereafter. In EGb 761-treated patients, MN increased early (P < 0.05), while returning toward baseline value thereafter. Therefore, mean MN increment was significantly higher in the placebo group as compared with EGb 761-treated patients (P < 0.01). Moreover, an early (P < 0.0001) and sustained (up to 35 d; P < 0.001) MN increase induced by CFs was observed in the placebo group. Conversely, in EGb 761-treated patients, MN increase induced by CFs never reached the statistical significance; therefore, the mean of the MN increments was significantly lower than in placebo (P < 0.05). A significant positive correlation between MN maximum increment and the bone marrow dose was observed in the placebo group only (P = 0.03). No significant difference was observed in clinical outcome between the two groups.

Conclusions: EGb 761 supplementation neutralized genotoxic damage induced by radioiodine treatment, without affecting the clinical outcome. Although ¹³¹I therapy is generally safe, our data suggest that Gingko biloba extracts may prevent genetic effects of radioiodine therapy for hyperthyroid Graves’ disease.