Background: The positive relationship between triiodothyronine (T3) and steatotic liver disease (SLD) demonstrated only in crosssectional study. We aimed to evaluated whether total T3 (TT3) is associated with the development/resolution of SLD in longitudinal design. Methods: This retrospective, longitudinal, population-based cohort study included 1,665 South Korean euthyroid adults with ≥4 thyroid function test. We explored the impact of mean TT3 during follow-up on development/resolution of either SLD (diagnosed by ultrasound) or modified metabolic dysfunction-associated steatotic liver disease (MASLD) using Cox proportional hazards regression models. Results: During about median 5 years follow-up, 807/1,216 (66.3%) participants among participants without SLD at baseline developed SLD, and 253/318 (79.5%) participants among participants with SLD at baseline SLD resolved fatty liver. Mean TT3 rather than thyroid stimulating hormone or mean free thyroxine was significantly related with development (adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 1.00 to 1.02; P=0.002) and resolution (adjusted HR, 0.97; 95% CI, 0.96 to 0.99; P=0.005) of SLD. Compared with low mean TT3 group, high mean TT3 group was positively associated with development of SLD (adjusted HR, 1.20; 95% CI, 1.05 to 1.38; P=0.008) and inversely associated with resolution of SLD (adjusted HR, 0.66; 95% CI, 0.51 to 0.85; P=0.001). The statistical significance remained for development (adjusted HR, 1.29; 95% CI, 1.10 to 1.51; P=0.001) and resolution (adjusted HR, 0.71; 95% CI, 0.54 to 0.94; P=0.018) of modified MASLD. Conclusion In Korean euthyroid adults, TT3 level was associated with development and resolution of either SLD or modified MASLD.

Background: The positive relationship between triiodothyronine (T3) and steatotic liver disease (SLD) demonstrated only in crosssectional study. We aimed to evaluated whether total T3 (TT3) is associated with the development/resolution of SLD in longitudinal design. Methods: This retrospective, longitudinal, population-based cohort study included 1,665 South Korean euthyroid adults with ≥4 thyroid function test. We explored the impact of mean TT3 during follow-up on development/resolution of either SLD (diagnosed by ultrasound) or modified metabolic dysfunction-associated steatotic liver disease (MASLD) using Cox proportional hazards regression models. Results: During about median 5 years follow-up, 807/1,216 (66.3%) participants among participants without SLD at baseline developed SLD, and 253/318 (79.5%) participants among participants with SLD at baseline SLD resolved fatty liver. Mean TT3 rather than thyroid stimulating hormone or mean free thyroxine was significantly related with development (adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 1.00 to 1.02; P=0.002) and resolution (adjusted HR, 0.97; 95% CI, 0.96 to 0.99; P=0.005) of SLD. Compared with low mean TT3 group, high mean TT3 group was positively associated with development of SLD (adjusted HR, 1.20; 95% CI, 1.05 to 1.38; P=0.008) and inversely associated with resolution of SLD (adjusted HR, 0.66; 95% CI, 0.51 to 0.85; P=0.001). The statistical significance remained for development (adjusted HR, 1.29; 95% CI, 1.10 to 1.51; P=0.001) and resolution (adjusted HR, 0.71; 95% CI, 0.54 to 0.94; P=0.018) of modified MASLD. Conclusion In Korean euthyroid adults, TT3 level was associated with development and resolution of either SLD or modified MASLD.

Background: The positive relationship between triiodothyronine (T3) and steatotic liver disease (SLD) demonstrated only in crosssectional study. We aimed to evaluated whether total T3 (TT3) is associated with the development/resolution of SLD in longitudinal design. Methods: This retrospective, longitudinal, population-based cohort study included 1,665 South Korean euthyroid adults with ≥4 thyroid function test. We explored the impact of mean TT3 during follow-up on development/resolution of either SLD (diagnosed by ultrasound) or modified metabolic dysfunction-associated steatotic liver disease (MASLD) using Cox proportional hazards regression models. Results: During about median 5 years follow-up, 807/1,216 (66.3%) participants among participants without SLD at baseline developed SLD, and 253/318 (79.5%) participants among participants with SLD at baseline SLD resolved fatty liver. Mean TT3 rather than thyroid stimulating hormone or mean free thyroxine was significantly related with development (adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 1.00 to 1.02; P=0.002) and resolution (adjusted HR, 0.97; 95% CI, 0.96 to 0.99; P=0.005) of SLD. Compared with low mean TT3 group, high mean TT3 group was positively associated with development of SLD (adjusted HR, 1.20; 95% CI, 1.05 to 1.38; P=0.008) and inversely associated with resolution of SLD (adjusted HR, 0.66; 95% CI, 0.51 to 0.85; P=0.001). The statistical significance remained for development (adjusted HR, 1.29; 95% CI, 1.10 to 1.51; P=0.001) and resolution (adjusted HR, 0.71; 95% CI, 0.54 to 0.94; P=0.018) of modified MASLD. Conclusion In Korean euthyroid adults, TT3 level was associated with development and resolution of either SLD or modified MASLD.

Background: The positive relationship between triiodothyronine (T3) and steatotic liver disease (SLD) demonstrated only in crosssectional study. We aimed to evaluated whether total T3 (TT3) is associated with the development/resolution of SLD in longitudinal design. Methods: This retrospective, longitudinal, population-based cohort study included 1,665 South Korean euthyroid adults with ≥4 thyroid function test. We explored the impact of mean TT3 during follow-up on development/resolution of either SLD (diagnosed by ultrasound) or modified metabolic dysfunction-associated steatotic liver disease (MASLD) using Cox proportional hazards regression models. Results: During about median 5 years follow-up, 807/1,216 (66.3%) participants among participants without SLD at baseline developed SLD, and 253/318 (79.5%) participants among participants with SLD at baseline SLD resolved fatty liver. Mean TT3 rather than thyroid stimulating hormone or mean free thyroxine was significantly related with development (adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 1.00 to 1.02; P=0.002) and resolution (adjusted HR, 0.97; 95% CI, 0.96 to 0.99; P=0.005) of SLD. Compared with low mean TT3 group, high mean TT3 group was positively associated with development of SLD (adjusted HR, 1.20; 95% CI, 1.05 to 1.38; P=0.008) and inversely associated with resolution of SLD (adjusted HR, 0.66; 95% CI, 0.51 to 0.85; P=0.001). The statistical significance remained for development (adjusted HR, 1.29; 95% CI, 1.10 to 1.51; P=0.001) and resolution (adjusted HR, 0.71; 95% CI, 0.54 to 0.94; P=0.018) of modified MASLD. Conclusion In Korean euthyroid adults, TT3 level was associated with development and resolution of either SLD or modified MASLD.

Background and Objectives: To analyze the clinical trends and treatment patterns of thyroid cancer in the recent decade in South Korea. Materials and Methods: Two distinctive datasets, a single institutional database from 2009 to 2021 of differentiated thyroid cancer (DTC) patients (n=3145) and a nationwide database of the Korean Cancer Center Registry (KCCR) from 2005 to 2019 for patients (n=414,828) with all types of thyroid cancer, were analyzed. Annual incidence, the extent of thyroidectomy and neck dissection, T and N stages, and postoperative radioactive iodine (RAI) were investigated and descriptively presented. Results: The institutional database demonstrated that the annual cases of DTC surgeries suddenly dropped in 2014, coinciding with a social debate on overdiagnosis in South Korea. Due to changes in the staging manual and management guidelines during the study period, lobectomy has been preferred more than total thyroidectomy and the number of anterior compartment neck dissections has decreased. However, cases with lateral neck dissection and T4 stage gradually increased, suggesting that social issue did not influence the incidence of advanced thyroid diseases. The KCCR database also supported a similar phenomenon that showed a recent increase in localized and regional disease after a shock from social controversy. Conclusion Our institutional and KCCR data findings collectively indicate a steady incidence in localized and regional thyroid cancer after the initial drop triggered by the 2014 controversy in South Korea.

Background and Objectives: Telomerase reverse transcriptase (TERT) promoter mutations are a poor prognostic factor in differentiated thyroid carcinoma (DTC). However, their prognostic value in anaplastic thyroid carcinoma (ATC) is unclear. Therefore, we investigated whether TERT promoter mutations also act as an independent poor prognostic factor in ATC. Materials and Methods: We reviewed the medical records of 41 patients with ATC who underwent the TERT promoter mutations test at Samsung Medical Center between November 1995 and December 2022. The aggressive treatment group was defined as patients who underwent surgery, external radiotherapy, and systemic therapy. Results: Among 41 patients, 15 (36.6%) showed TERT promoter mutations. There only differences in the clinicopathological characteristics between the TERT-mutant and wild-type groups were tumor size and coexistence of DTC. Median tumor size in the TERT-mutant group was 5.1 cm (3.0-11.0), which was significantly larger than that in the wild-type group (4.1 cm, 0.8-8.0, p=0.010). Nevertheless, the TERT-mutant group received relatively more aggressive treatment (53.3% vs. 19.2%, p=0.056), and the overall survival of the TERT-mutant group was longer than that of the wild-type group (9.4 months [0.4-51.5] vs. 7.1 months [0.4-49.5]), but its difference was not significant (p=0.458). In multiple regression analysis, distant metastasis was a significant prognostic factor, but TERT promoter mutation was not. Conclusion Unlike in DTC, TERT promoter mutations were not an independent poor prognostic factor in ATC.

Thyroid scanning using technetium-99m ( 99mTc) is the gold standard for diagnosing feline hyperthyroidism. In cats with an overactive thyroid, a thyroid scan is the most appropriate imaging technique to detect and localize any hyperfunctional adenomatous thyroid tissue. In this study, the pharmacological properties of the Technekitty injection (Tc-99m), developed as a diagnostic agent for feline hyperthyroidism using 99mTc as an active ingredient, were tested in FRTL-5 thyroid follicular cell line and ICR mice. The percentage of cell uptake of the Tc-99m in FRTL-5 thyroid cells was 0.182 ± 0.018%, which was about 6 times higher compared to Clone 9 hepatocytes. This uptake decreased by 38.2% due to competitive inhibition by iodine (sodium iodide). In tissue distribution tests by using ICR mice, the highest distribution was observed in the liver, kidneys, spleen, lungs, and femur at 0.083 hours after administration, and this distribution decreased as the compound was excreted through the kidneys, the pri-mary excretory organ. Maximum distribution was confirmed at 1 hour in the small intestine, 6hours in the large intestine, and 2 hours in the thyroid gland. Additionally, the total amount excreted through urine and feces over 48 hours (2 days) was 78.80% of the injected dose, with 37.70% (47.84% of the total excretion) excreted through urine and 41.10% (52.16% of the total excretion) through feces. In conclusion, the Tc-99m has the same mechanism of action, potency, absorption, distribution, metabolism, and excretion characteristics as 99mTc used for feline hyperthyroidism in the United States, Europe, and other countries, because the Technekitty injection (Tc-99m) contains 99mTc as its sole active ingredient. Based on these results, the Technekitty injection (Tc-99m) is expected to be safely used in the clinical diagnosis of feline hyperthyroidism.

Background and Objectives: To analyze the clinical trends and treatment patterns of thyroid cancer in the recent decade in South Korea. Materials and Methods: Two distinctive datasets, a single institutional database from 2009 to 2021 of differentiated thyroid cancer (DTC) patients (n=3145) and a nationwide database of the Korean Cancer Center Registry (KCCR) from 2005 to 2019 for patients (n=414,828) with all types of thyroid cancer, were analyzed. Annual incidence, the extent of thyroidectomy and neck dissection, T and N stages, and postoperative radioactive iodine (RAI) were investigated and descriptively presented. Results: The institutional database demonstrated that the annual cases of DTC surgeries suddenly dropped in 2014, coinciding with a social debate on overdiagnosis in South Korea. Due to changes in the staging manual and management guidelines during the study period, lobectomy has been preferred more than total thyroidectomy and the number of anterior compartment neck dissections has decreased. However, cases with lateral neck dissection and T4 stage gradually increased, suggesting that social issue did not influence the incidence of advanced thyroid diseases. The KCCR database also supported a similar phenomenon that showed a recent increase in localized and regional disease after a shock from social controversy. Conclusion Our institutional and KCCR data findings collectively indicate a steady incidence in localized and regional thyroid cancer after the initial drop triggered by the 2014 controversy in South Korea.

Background and Objectives: Telomerase reverse transcriptase (TERT) promoter mutations are a poor prognostic factor in differentiated thyroid carcinoma (DTC). However, their prognostic value in anaplastic thyroid carcinoma (ATC) is unclear. Therefore, we investigated whether TERT promoter mutations also act as an independent poor prognostic factor in ATC. Materials and Methods: We reviewed the medical records of 41 patients with ATC who underwent the TERT promoter mutations test at Samsung Medical Center between November 1995 and December 2022. The aggressive treatment group was defined as patients who underwent surgery, external radiotherapy, and systemic therapy. Results: Among 41 patients, 15 (36.6%) showed TERT promoter mutations. There only differences in the clinicopathological characteristics between the TERT-mutant and wild-type groups were tumor size and coexistence of DTC. Median tumor size in the TERT-mutant group was 5.1 cm (3.0-11.0), which was significantly larger than that in the wild-type group (4.1 cm, 0.8-8.0, p=0.010). Nevertheless, the TERT-mutant group received relatively more aggressive treatment (53.3% vs. 19.2%, p=0.056), and the overall survival of the TERT-mutant group was longer than that of the wild-type group (9.4 months [0.4-51.5] vs. 7.1 months [0.4-49.5]), but its difference was not significant (p=0.458). In multiple regression analysis, distant metastasis was a significant prognostic factor, but TERT promoter mutation was not. Conclusion Unlike in DTC, TERT promoter mutations were not an independent poor prognostic factor in ATC.

Thyroid scanning using technetium-99m ( 99mTc) is the gold standard for diagnosing feline hyperthyroidism. In cats with an overactive thyroid, a thyroid scan is the most appropriate imaging technique to detect and localize any hyperfunctional adenomatous thyroid tissue. In this study, the pharmacological properties of the Technekitty injection (Tc-99m), developed as a diagnostic agent for feline hyperthyroidism using 99mTc as an active ingredient, were tested in FRTL-5 thyroid follicular cell line and ICR mice. The percentage of cell uptake of the Tc-99m in FRTL-5 thyroid cells was 0.182 ± 0.018%, which was about 6 times higher compared to Clone 9 hepatocytes. This uptake decreased by 38.2% due to competitive inhibition by iodine (sodium iodide). In tissue distribution tests by using ICR mice, the highest distribution was observed in the liver, kidneys, spleen, lungs, and femur at 0.083 hours after administration, and this distribution decreased as the compound was excreted through the kidneys, the pri-mary excretory organ. Maximum distribution was confirmed at 1 hour in the small intestine, 6hours in the large intestine, and 2 hours in the thyroid gland. Additionally, the total amount excreted through urine and feces over 48 hours (2 days) was 78.80% of the injected dose, with 37.70% (47.84% of the total excretion) excreted through urine and 41.10% (52.16% of the total excretion) through feces. In conclusion, the Tc-99m has the same mechanism of action, potency, absorption, distribution, metabolism, and excretion characteristics as 99mTc used for feline hyperthyroidism in the United States, Europe, and other countries, because the Technekitty injection (Tc-99m) contains 99mTc as its sole active ingredient. Based on these results, the Technekitty injection (Tc-99m) is expected to be safely used in the clinical diagnosis of feline hyperthyroidism.