The clinical data of a patient with differentiated thyroid carcinoma(DTC)who developed physiological thymic uptake after postoperative iodine-131(131I)therapy were analyzed,and the 3-year follow-up changes in the patient's condition were reviewed.Combined with the literatures and the diagnosis and treatment process,the causes of possible false positives in whole-body scans after iodine therapy for DTC and the mechanism,clinical features,and identification methods of benign thymic 131I uptake were discussed to improve clinicians' understanding and diagnostic ability regarding such conditions and avoid unnecessary multiple iodine treatments.The patient,a 28-year-old female,showed mediastinal imaging after the first 131I treatment,with more pronounced mediastinal iodine uptake during the second treatment.SPECT/CT localized the uptake to enlarged thymus tissue.The stimulated thyroglobulin(Tg)levels before two 131I treatments were high but gradually decreased.Apart from thymic uptake,no other examination evidence suggested DTC metastases.Subsequent follow-up for 3 years showed no pathological changes in the thymus,confirming physiological thymic uptake.Thymic 131I uptake is a common cause of false-positive whole-body scans in post-thyroidectomy patients.When post-131I therapy whole-body imaging shows only mediastinal uptake,especially in the young patients undergoing multiple 131I treatments where thymic 131I uptake intensity increases with successive treatments,even with elevated Tg levels,comprehensive use of imaging results such as SPECT/CT is essential to determine if it is normal thymus,thereby avoiding unnecessary repeated therapies.

Intestinal dysbiosis and disrupted bile acid(BA)homeostasis are associated with obesity,but the precise mechanisms remain insufficiently explored.Hepatic protein phosphatase 1 regulatory subunit 3G(PPP1R3G)plays a pivotal role in regulating glycolipid metabolism;nevertheless,its obesity-combatting potency remains unclear.In this study,a substantial reduction was observed in serum PPP1R3G levels in high-body mass index(BMI)and high-fat diet(HFD)-exposed mice,establishing a positive correlation between PPP1R3G and non-12α-hydroxylated(non-12-OH)BA content.Additionally,hepatocyte-specific overexpression of Ppp1r3g(PPP1R3G HOE)mitigated HFD-induced obesity as evidenced by reduced weight,fat mass,and an improved serum lipid profile;hepatic steatosis alleviation was confirmed by normalized liver enzymes and histology.PPP1R3G HOE considerably impacted systemic BA homeostasis,which notably increased the non-12-OH BAs ratio,particularly lithocholic acid(LCA).16S ribosomal DNA(16S rDNA)sequencing assay indicated that PPP1R3G HOE reversed HFD-induced gut dysbiosis by reducing the Firmicutes/Bacteroidetes ratio and Lactobacillus population,and elevating the relative abundance of Blautia,which exhibited a positive correlation with serum LCA levels.A fecal microbiome transplantation test confirmed that the anti-obesity effect of hepatic PPP1R3G was gut microbiota-dependent.Mechanistically,PPP1R3G HOE markedly suppressed hepatic cholesterol 7α-hydroxylase(CYP7A1)and sterol-12α-hydroxylase(CYP8B1),and concurrently upregulated oxysterol 7-α hydroxylase and Takeda G protein-coupled BA receptor 5(TGR5)expression under HFD conditions.Furthermore,LCA administration significantly mitigated the HFD-induced obesity phenotype and elevated non-12-OH BA levels.These findings emphasize the significance of hepatic PPP1R3G in ameliorating diet-induced adiposity and hepatic steatosis through the gut microbiota-BA axis,which may serve as potential ther-apeutic targets for obesity-related disorders.