Radioactive iodine therapy has been a well-established treatment for various thyroid conditions since the 1940s, targeting both benign diseases and malignancies. Treatment for benign conditions typically involves low doses of 131I, often requiring no more than two treatments, with the dose either fixed or personalized based on thyroid tissue mass and iodine uptake. In contrast, differentiated thyroid cancer treatment often requires higher doses and multiple administrations, especially for metastatic cases. Recent guidelines and studies have proposed more conservative management strategies, including careful follow-up, due to concerns over the high risk–benefit ratio in selected cases with a low risk of disease recrudescence. Despite its possible efficacy, radioiodine therapy is associated with dose-dependent side effects, the most common of which is salivary gland dysfunction or inflammation, affecting approximately 30% of adult patients. These effects pose significant challenges in nuclear medicine practice. This review aims to summarize the latest evidence on the incidence, impact on quality of life, prevention strategies and the role of these side effects in the decision-making process regarding RAI therapy.

Background: Struma ovarii (SO) is an ovarian teratoma with the presence of ectopic thyroid tissue. Differentiated thyroid cancer (DTC) in SO is a rare finding. Management of DTC in SO is currently not clearly established. We performed a systematic review of the literature to assess the role of 131I radiometabolic therapy in the treatment of DTC in SO. Methods: a wide literature search in the Scopus, PubMed/MEDLINE, and Web of Science databases was made to find published articles regarding the treatment of patients with DTC and SO. The quality assessment of studies was performed by QUADAS-2 evaluation. Results: eleven studies were included in the systematic review. All of them were retrospective studies and/or case series, and two of them also included a review of the literature. Most of the studies describe cases of DTC in SO treated by total thyroidectomy (TT) and subsequent radioiodine (RAI) therapy, especially in patients with distant metastases and/or concomitant thyroid cancer. However, the majority of patients apparently did not require radiometabolic therapy. Conclusions: TT and subsequent RAI therapy is usually performed in metastatic disease, not recommended in patients with intraovarian disease without risk factors, and it appeared possible but not mandatory in patients with risk factors.

Differentiated thyroid carcinoma (DTC) is the most common malignant endocrine tumor, with a generally favorable prognosis. Imaging, including iodine radioactive isotope scintigraphy (IRIS), is crucial for diagnosis and follow-up. While ¹³¹I has long been used for both therapeutic and diagnostic purposes, ¹²³I is reserved for diagnostic imaging due to its shorter half-life and γ emissions. This review highlights the utility of ¹²³I scintigraphy, especially in pre-treatment assessment and dosimetry for DTC. It is particularly valuable before radioiodine (RAI) ablation, providing accurate imaging in patients with iodine-refractory (IR) or biochemically incomplete response (BIR) DTC. When compared to post-therapeutic ¹³¹I scans, ¹²³I scintigraphy appears to have a lower sensitivity for detecting metastatic lesions, particularly in lymph nodes and lungs. However, its diagnostic performance compared to low-dose diagnostic ¹³¹I is more variable, with some studies suggesting superiority due to the absence of stunning. Further research is needed to standardize its use and optimize its role in guiding DTC management.