Vitamin D deficiency affects thyroid autoimmunity and dysfunction in iodine-replete area: Korea national health and nutrition examination survey.

PURPOSE: We evaluated the effects of vitamin D levels and iodine intake on thyroid autoimmunity and dysfunction in the Korean population. METHODS: In this nationwide population-based study, data were obtained from the Korea National Health and Nutrition Examination Survey VI-1 and 2 (2013 and 2014), which was the first nationwide survey that measured both serum 25-hydroxy vitamin D [25(OH)D] levels and urinary iodine concentrations (UICs) in Korea. A total of 4181 participants who underwent laboratory tests for thyroid function, serum 25(OH)D levels, and UICs were included. RESULTS: Anti-thyroid peroxidase antibody (TPOAb) positivity was more prevalent in the vitamin D deficient group (9.1%) than the vitamin D insufficient and sufficient groups (5.3% each; P = 0.016). The rate of TPOAb positivity was significantly higher in the iodine deficient group (P = 0.032). Thyroid dysfunction was significantly more prevalent in the iodine excessive group than in the other groups in total (P = 0.016) and TPOAb negative participants (P = 0.007). In the vitamin D deficient group, excessive iodine intake was significantly associated with high prevalence of thyroid dysfunction in total and TPOAb negative participants (P = 0.021 and P = 0.033, respectively). In the vitamin D insufficient and sufficient groups, association between thyroid dysfunction and iodine intake disappeared in total and TPOAb negative participants. CONCLUSIONS: This nationwide survey revealed a significant association between vitamin D deficiency and high prevalence of thyroid autoimmunity and dysfunction in participants with excessive iodine intake. Our findings might be helpful for elucidating the potential benefit of vitamin D supplements in TPOAb negative patients with excessive iodine intake.

Dynamic Risk Stratification in Stage I Papillary Thyroid Cancer Patients Younger Than 45 Years of Age.

BACKGROUND: This study validated the dynamic risk stratification (DRS) system with regard to its association with structural recurrence and risk factors associated with non-excellent responses in patients <45 years with stage I classical papillary thyroid cancer (PTC). METHODS: This historical cohort study included 598 patients with stage I classical PTC <45 years of age treated with total thyroidectomy followed by radioactive iodine remnant ablation (n = 440), total thyroidectomy without radioactive iodine remnant ablation (n = 23), and thyroid lobectomy alone (n = 135). RESULTS: The median follow-up period was 123 months. Structural recurrence occurred in 4.2% (n = 18/432) of the patients with an excellent response, 17.1% (18/105) of patients with an indeterminate response, 44.7% (17/38) of patients with a biochemically incomplete response, and 82.6% (19/23) of patients with a structurally incomplete response (p < 0.001) during the follow-up. The disease-free survival curves of each response showed significant differences (p < 0.001). Extensive extrathyroidal extension and extranodal extension were the independent risk factors associated with non-excellent response (p < 0.05). CONCLUSIONS: DRS may reduce unnecessary additional treatments by reclassifying initial risk estimates of structural recurrence. Furthermore, applying the risk factors associated with non-excellent response to initial therapy may be a more useful and viable surrogate of the risk for structural recurrence in stage I PTC patients <45 years of age.

Lack of Efficacy of Radioiodine Remnant Ablation for Papillary Thyroid Microcarcinoma: Verification Using Inverse Probability of Treatment Weighting.

BACKGROUND: Most of the increase in thyroid cancer in recent decades has been due to papillary thyroid microcarcinoma (PTMC). We evaluated the efficacy of radioiodine remnant ablation (RRA) in patients with PTMC. METHODS: This historical cohort study included 1932 PTMC patients without lateral cervical lymph node (LN) or distant metastasis who underwent total thyroidectomy (TT) during the median 8.3 years of follow-up. The clinical outcomes of patients with or without RRA were compared using weighted logistic regression models with the inverse probability of treatment weighting (IPTW) method and considering risk factors, including age, sex, primary tumor size, extrathyroidal extension, multifocality, and central cervical LN metastasis. RESULTS: The median primary tumor size of the RRA group was significantly larger than that of the no-RRA group (0.7 vs. 0.5 cm, P < 0.001). There were significantly more patients with multifocality, extrathyroidal extension, and cervical LN metastasis in the RRA group compared with the no-RRA group. There was no significant difference in recurrence-free survival between the two groups (P = 0.11). Cox proportional-hazard analysis with IPTW by adjusting for clinicopathological risk factors demonstrated no significant difference in recurrence of PTMC according to RRA treatment (hazard ratio [HR] 2.02; 95% confidence interval [CI] 0.65-6.25; P = 0.2). CONCLUSIONS: RRA had no therapeutic effect on the clinical outcomes of patients with PTMC who underwent TT. Surgical treatment without RRA could be applicable for patients with PTMC if there is no evidence of lateral cervical LN metastasis or distant metastasis.

Changes in the pulmonary function test after radioactive iodine treatment in patients with pulmonary metastases of differentiated thyroid cancer.

OBJECTIVE: Pulmonary function test (PFT) is a useful tool for an objective assessment of respiratory function. Impaired pulmonary function is critical for the survival and quality of life in patients with pulmonary metastases of solid cancers including thyroid cancer. This study aimed to evaluate clinical factors associated with severely impaired pulmonary function by serial assessment with PFT in patients with pulmonary metastasis of differentiated thyroid cancer (DTC) who received radioactive iodine treatment (RAIT). PATIENTS: This retrospective study enrolled 31 patients who underwent serial PFTs before and after RAIT for pulmonary metastasis of DTC. We evaluated the risk factors for severe impairment of pulmonary function. RESULTS: The median age of the patients was 44.1 years and 18 of them were female patients. Severe impairment of pulmonary function was observed in five patients (16%) after a median of three RAITs (cumulative I-131 activity = 20.4 GBq). These patients were older and more frequently had mild impairment of baseline pulmonary function, respiratory symptoms, or progressive disease compared with patients with stable pulmonary function. Neither cumulative dose nor number of RAIT was associated with decreased pulmonary function. Coexisting pulmonary diseases, presence of respiratory symptoms, and metastatic disease progression were significantly associated with severe decrease in forced vital capacity during follow-up (p =.047, p =.011, and p =.021, respectively). CONCLUSIONS: Pulmonary function was severely impaired during follow-up in some patients with pulmonary metastasis of DTC after a high-dose RAITs. Neither the number of RAIT nor the cumulative I-131 activity was associated with decreased pulmonary function. Serial PFT might be considered for some high-risk patients during follow-up.