(1) Background: Thyroid tissue ablation with radioactive iodine (RAI) has been successfully used in the treatment of differentiated thyroid cancers. However, as a side effect, RAI may induce salivary gland (SG) hypofunction, which has been alternatively managed with photobiomodulation therapy (PBMT). In our study, we assessed the effects of RAI on the SGs and further analyzed whether PBMT can minimize tissue damage. (2) Methods: Balb/c mice were allocated into three groups, as follows: RI, submitted to RAI orally; RIL, similar to RI, but with PBMT for SG hypofunction; and C, control group. The animals were euthanized on days 0, 10, and 90 after RAI. (3) Results: A decrease in tri-iodothyronine (T3) and thyroxine (T4) serum levels was observed both in the RI and RIL groups. In addition, a decrease in SG weight and morphological alterations were shown in the RI group throughout the experimental period, as well as a significant increase in total protein and peroxidase concentrations, and catalase activity. On day 90, the RI group presented less collagen and fewer sodium/iodine channels, with higher rates of cell apoptosis. Pertechnetate (Na99mTcO4) uptake was also affected in the RI group in all experimental times. Interestingly, although the RIL group also presented some alterations regarding these parameters, they were not statistically different from those of the C group on day 90. (4) Conclusions: Our results provide evidence that RAI induces harmful effects on the SGs, which can be successfully managed with PBMT.
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