[Influence of glucocorticoid therapy on intratherapeutic biodistribution of 131I radioiodine therapy in Graves' disease].

[Influence of glucocorticoid therapy on intratherapeutic biodistribution of 131I radioiodine therapy in Graves' disease].

Nuklearmedizin. 2018 Apr;57(2):43-49

Authors: Halstenberg J, Kranert WT, Korkusuz H, Mayer A, Ackermann H, Grünwald F, Happel C

Abstract
AIM: Radioiodine therapy (RIT) is an important therapeutic method in the definitive treatment of Graves' disease (GD). However, RIT may trigger development of Graves' ophthalmopathy (GO) or exacerbate a pre-existing GO. Therefore, the procedure recommendation of the DGN (German Society of Nuclear Medicine) for RIT of benign thyroid diseases recommends an additional glucocorticoid therapy for patients with pre-existing GO. Aim of this study was to analyze the influence of a protective glucocorticoid therapy on 131I biokinetics during RIT of patients with GD.
MATERIAL AND METHODS: In this retrospective analysis 211 patients with GD who underwent RIT without additional thyreostatic medication were examined. To analyze 131I biokinetics the extrapolated maximum uptake (EMU) and the effective half-life of 131I in the thyroid were determined. Patients suffering from GO received glucocorticoids according to a fixed scheme starting one day prior to RIT, patients without GO did not receive glucocorticoids. Subsequently the ratios of values measured during RIT and those measured during radioactive iodine uptake test were compared among the groups. To take into account other factors, the groups were also compared regarding age, weight, TSH, TRAb, TgAb and TPOAb.
RESULTS: In patients with additional glucocorticoid therapy, a reduction of the median EMU from 44 % in radioiodine uptake test to 35 % during RIT was observed. The pretherapeutic (47 %) and intratherapeutic (46 %) EMU of the control group without glucocorticoids remained constant. Comparison of the change in the EMU showed a statistically significant difference between both groups (p < 0.001). Comparison of all other parameters including the effective half-life of 131I (p = 0.79) did not show any statistically significant difference.
CONCLUSION: The present study suggests that glucocorticoids affect the biokinetics of 131I by reducing its thyroidal uptake. As a result of this study, for patients without antithyroid medication undergoing glucocorticoid therapy, an adjustment of therapeutic 131I activity determined in radioiodine uptake test could be considered.

PMID: 29590674 [PubMed - in process]

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