Objective: Little is known about the role of estrogen in thyroid cancer development. We aimed to evaluate the association between hysterectomy or bilateral salpingo-oophorectomy (BSO) and the risk of subsequent thyroid cancer. Design: A nationwide cohort study. Methods: Data from the Korea National Health Insurance Service between 2002 and 2017 were used. A total of 78,961 and 592,330 women were included in the surgery group and no surgery group, respectively. The surgery group was categorized into two groups according to the extent of surgery: hysterectomy with ovarian conservation (hysterectomy-only) and BSO with or without hysterectomy (BSO). Results: During 8,086,396.4 person-years of follow-up, 12,959 women developed thyroid cancer. Women in the hysterectomy-only (adjusted hazard ratio = 1.7, P < 0.001) and BSO (adjusted hazard ratio = 1.4, P < 0.001) groups had increased risk of thyroid cancer compared to those in the no surgery group. In premenopausal women, hysterectomy-only (adjusted hazard ratio = 1.7, P < 0.001) or BSO (adjusted hazard ratio = 1.4, P < 0.001) increased the risk of subsequent thyroid cancer, irrespective of hormone therapy, whereas, there was no significant association between hysterectomy-only (P = 0.204) or BSO (P = 0.857) and thyroid cancer development in postmenopausal women who had undergone hormone therapy. Conclusions: Our findings do not support the hypotheses that sudden or early gradual decline in estrogen levels is a protective factor in the development of thyroid cancer, or that exogenous estrogen is a risk factor for thyroid cancer.

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Background: Only few studies have shown the efficacy and safety of glucose-control strategies using the quadruple drug combination. Therefore, the aim of the present study was to investigate the usefulness of the quadruple combination therapy with oral hypoglycemic agents (OHAs) in patients with uncontrolled type 2 diabetes mellitus (T2DM). Methods: From March 2014 to December 2018, data of patients with T2DM, who were treated with quadruple hypoglycemic medications for over 12 months in 11 hospitals in South Korea, were reviewed retrospectively. We compared glycosylated hemoglobin (HbA1c) levels before and 12 months after quadruple treatment with OHAs. The safety, maintenance rate, and therapeutic patterns after failure of the quadruple therapy were also evaluated. Results: In total, 357 patients were enrolled for quadruple OHA therapy, and the baseline HbA1c level was 9.0%±1.3% (74.9±14.1 mmol/mol). After 12 months, 270 patients (75.6%) adhered to the quadruple therapy and HbA1c was significantly reduced from 8.9%±1.2% to 7.8%±1.3% (mean change, −1.1%±1.2%; P <0.001). The number of patients with HbA1c <7% increased significantly from 5 to 68 ( P <0.005). In addition, lipid profiles and liver enzyme levels were also improved whereas no changes in body weight. There was no significant safety issue in patients treated with quadruple OHA therapy. Conclusion: This study shows the therapeutic efficacy of the quadruple OHA regimen T2DM and demonstrates that it can be an option for the management of T2DM patients who cannot use insulin or reject injectable therapy.

Background: Studies on the relationship between thyroid function and anemia in the euthyroid range are scarce. We aimed to evaluate the association between anemia and serum free thyroxine (fT4) and thyrotropin (TSH) in euthyroid adults. Methods: Data on 5,352 participants aged ≥19 years were obtained from the Korea National Health and Nutrition Examination Survey VI (2013 to 2015). Anemia was defined as hemoglobin (Hb) <13 and <12 g/dL for men and women, respectively. Results: Overall, 6.1% of participants had anemia, and more women (9.9%) had anemia than men (2.8%, P<0.001). In multivariate analysis, serum fT4 levels, but not TSH, were positively associated with serum Hb levels in both sexes (P<0.001, each). Serum Hb levels linearly reduced across decreasing serum fT4 quartile groups in both sexes (P<0.001, each). After adjusting for potential confounding factors, participants with low-normal fT4 had 4.4 (P=0.003) and 2.8 times (P<0.001) higher risk for anemia than those with high-normal fT4 among men and women, respectively. When participants were divided into two groups at 50 years of age, in younger participants, men and women with the first quartile were at higher risk of anemia than men with the second quartile (odds ratio [OR], 3.3; P=0.029) and women with the forth quartile (OR, 3.2; P<0.001), respectively. This association was not observed in older participants. Conclusion: These results suggest that a low-normal level of serum fT4 was associated with a lower serum Hb level and a higher risk of anemia in euthyroid adults, especially in younger participants.

After thyroidectomy in differentiated thyroid cancer (DTC), radioactive iodine (RAI) treatment is often used for remnant ablation. However, RAI treatment has been associated with bone marrow suppression, and leukopenia, anemia, and thrombocytopenia may occur after a single RAI administration. In this study, we examined the change in complete blood counts at 1 week after RAI administration; this is less well studied. A group of 189 DTC patients who received RAI treatment and underwent blood tests before and after treatment, were included. Peripheral blood counts at baseline were compared to those obtained at 1 week, 1-6 months, and 6-12 months after RAI treatment in order to test for bone marrow suppression. At 1 week after RAI treatment, there was a significant decrease in the white blood cell count (WBC, 5.8 ± 1.6 × 10 9 /L vs. 5.4 ± 1.5 × 10 9 /L, p < 0.001) and hemoglobin level (Hb, 13.5 ± 1.7 g/dL vs. 13.3 ± 1.4 g/dL, p = 0.001). The WBC decrease was mostly due to lymphocyte counts (2.2 ± 0.6 × 10 9 /L vs. 1.6 ± 0.5 × 10 9 /L, p < 0.001), with no decrease in the neutrophil count. Although not significantly changed at 1 week, platelets counts were altered within 6 months (265 ± 69 × 10 9 /L vs. 239 ± 53 × 10 9 /L, p < 0.001). The decline in the WBC count recovered within 6 months; lymphocyte and platelet counts recovered within 12 months. In conclusion, RAI treatment after a thyroidectomy was associated with a statistically significant but temporary decline in WBC counts and Hb levels at 1 week. Physicians treating DTC patients should not decrease usage of moderate dose RAI treatments.