Journal Article

FZJ-2026-04028

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Radioiodine Exhalation Following Oral I-131 Administration in a Mouse Model

Schomäcker, K. (Corresponding author) ; Fischer, T. ; Sudbrock, F. ; Strohe, D. ; Weber, S. ; Zimmermanns, B. ; Dietlein, F. ; Krapf, P.FZJ* ; Schicha, H. ; Dietlein, M. ; Drzezga, A.FZJ*

2025
MDPI Basel

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Please use a persistent id in citations: doi:10.3390/biomedicines13040897  doi:10.34734/FZJ-2026-04028

Abstract: Background: The exhalation of radioiodine following radioiodine therapy (RIT) presents a challenge in radiation protection, though the mechanisms remain incompletely understood. Previous studies have indicated that radioiodine is predominantly exhaled in an organically bound form in humans. Methods: This study investigates the chemical composition and exhaled amounts of radioiodine, as well as the impact of thyroid-targeted pharmacological interventions, using a controlled mouse model. Female Balb/c mice (25 g) were administered oral doses of radioiodine (0.1, 1, 2, 10, and 23 MBq per animal) with and without prior treatment using thyroid-blocking agents (stable iodine, perchlorate) or antithyroid drugs (carbimazole). Exhaled radioiodine was collected in metabolic cages, separating chemical forms (aerosolized iodine, elemental iodine, organically bound iodine), and quantified via scintillation counter. Results: The exhaled radioiodine activity was proportional to the administered dose (0.2-0.3%). Thyroid-blocking agents increased exhalation, shifting toward elemental iodine. Antithyroid drugs reduced exhalation but increased aerosol formation, particularly at higher I-131 doses. Organically bound iodine remained the predominant exhaled species in all groups. Conclusions: These results highlight the critical role of the thyroid in radioiodine organification. The blockade of thyroid uptake disrupted the formation of organically bound iodine, suggesting that iodine organification requires passage through the thyroid. Additionally, the results support the hypothesis that iodine metabolism outside the thyroid is less efficient, contributing to the formation of organic iodine species. Radical formation is likely a key factor in generating these volatile iodine species, with radiation-induced iodine and methyl radicals playing a role in their formation.

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Contributing Institute(s):

1. Nuklearchemie (INM-5)

Research Program(s):

1. 5253 - Neuroimaging (POF4-525) (POF4-525)

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