Euthyroid Adults Research Articles

Association between ambient temperature and thyroid-stimulating hormone and free thyroxine levels in Korean euthyroid adults

Association between ambient temperature and thyroid-stimulating hormone and free thyroxine levels in Korean euthyroid adults

TSH is independently associated with remnant cholesterol in euthyroid adults: a cross-sectional study based on 29,708 individuals.

The study aims to investigate the relationship between thyroid-stimulating hormone (TSH) and remnant cholesterol (RC) in euthyroid adults. The adults who were recruited for the study had undergone physical examination at Beijing Chao-Yang Hospital. High RC levels were defined as the upper quartile of RC levels in males and females, respectively. The relationship between TSH and RC was assessed using the logistic and linear regression models. A total of 29,708 adults (14,347 males and 15,361 females) were enrolled in this study. RC ≥ 0.77 mmol/L in males and RC ≥ 0.60 mmol/L in females were defined as high RC levels. With increasing serum TSH levels, the percentage of adults with high RC levels increased. The odds ratios (ORs (95% confidence intervals (CIs)) for high RC levels increased as TSH quartiles (Q) rose after full adjustments [males: Q2 1.11 (1.00-1.24), P < 0.05; Q3 1.03 (0.92-1.15), P > 0.05; Q4 1.25 (1.12-1.40), P < 0.001; and females: Q2 1.07 (0.96-1.20), P > 0.05; Q3 1.17 (1.05-1.31), P < 0.01, Q4 1.33 (1.20-1.48), P < 0.001, all P for trend < 0.001], using Q1 as the reference. Higher TSH levels were independently associated with higher RC levels in euthyroid adults, this underscoring the significance of regulating TSH levels appropriately.

Correlation between thyroid hormone sensitivity and diabetic peripheral neuropathy in euthyroid patients with type 2 diabetes mellitus

Previous studies have revealed that thyroid hormone (TH) levels are associated with the risk of diabetic peripheral neuropathy (DPN) in euthyroid patients with type 2 diabetes mellitus (T2DM). However, the relationship between TH sensitivity, a complementary method for assessing thyroid function, and DPN remains unclear. This study aimed to investigate the correlation between DPN and TH sensitivity in euthyroid patients with T2DM. Exactly 708 euthyroid adults with T2DM were retrospectively enrolled. The FT3/FT4 ratio was used to estimate peripheral TH sensitivity. Central TH sensitivity was assessed using the Thyrotroph T4 Resistance Index (TT4RI), Thyroid-Stimulating Hormone Index (TSHI), Thyroid Feedback Quantile-based Index (TFQI), and Parametric TFQI (PTFQI). DPN was assessed using neurologic symptoms, signs, and nerve conduction velocity tests. The relationship between DPN and TH sensitivity was examined using logistic regression analysis. We observed that an elevated FT3/FT4 ratio was associated with DPN (OR = 1.36, 95%CI: 1.13–1.63, p = 0.0012). For each standard deviation (SD) increase in the TT4RI, TSHI, TFQI, and PTFQI, the OR of DPN was 0.80 (95%CI: 0.68–0.94, p = 0.0078), 0.72 (95%CI: 0.60–0.86, p = 0.0002), 0.69 (95%CI: 0.58–0.83, p < 0.0001), and 0.69 (95%CI: 0.58–0.82, p < 0.0001), respectively. These results suggested that reduced central and peripheral TH sensitivity is associated with a decreased risk of developing DPN.

Association between thyroid hormone resistance and obesity: a cross-sectional study and mouse stimulation test.

Thyroid hormone influences key metabolic pathways, and reduced sensitivity to thyroid hormone is considered a new risk factor for adverse metabolic outcomes. However, the association between thyroid hormone resistance and obesity in euthyroid individuals is still unknown. We enrolled 8021 euthyroid individuals, calculated thyroid hormone resistance indices, and analyzed the association between thyroid hormone resistance and obesity by regression analysis. Furthermore, we conducted the thyrotropin-releasing hormone stimulation test in both control and obese mice (n = 5) to demonstrate the association. The euthyroid adults with overweight and obesity had increased thyroid hormone resistance indices (all p < 0.05). BMI and prevalence of overweight and obesity increased (odds ratio of thyroid feedback quantile-based index [ORTFQI] = 1.164, p = 0.036; OR of free triiodothyronine/free thyroxine [ORFT3/FT4] = 1.508, p < 0.001) following the elevation of thyroid hormone resistance indices. Mediation analysis indicated a complete mediation effect (beta coefficient of indirect effect [βInd]= 6.838, p < 0.001) of metabolic disorders in the relationship. Furthermore, in the mice with obesity, the thyrotropin response to thyrotropin-releasing hormone stimulation (68.33-90.89 pg/mL) was comparatively blunted (p = 0.029). Euthyroid individuals with obesity exhibit both central and peripheral thyroid hormone resistance, a phenomenon that is more pronounced in individuals with metabolic abnormalities. Thyroid hormone resistance is associated with an increased prevalence of overweight and obesity mediated by metabolic disorders.

Correlation analysis between serum free triiodothyronine and C-peptide-based insulin resistance index in euthyroid adults

Objective: To explore the correlation between serum free triiodothyronine (FT3) and C-peptide-based insulin resistance index (HOMA2 IR-CP) in euthyroid adults. Methods: A cross-sectional study. The clinical data of euthyroid adult participants who underwent physical examination in the Second Medical Center of Chinese PLA General Hospital from January to December in 2019 were retrospectively analyzed. According to the HOMA2 IR-CP level, the participants were divided into HOMA2 IR-CP>2.18 group (n=3 463) and HOMA2 IR-CP≤2.18 group (n=8 204). Univariate Pearson correlation analysis and multivariate logistic regression analysis were used to analyze the correlation between FT3 and HOMA2 IR-CP. The interaction model was used to analyze the interaction between FT3 and related factors, and the dose-response relationship between continuity variable FT3 and HOMA2 IR-CP was explored by using restricted cubic spline plots. Results: A total of 11 667 euthyroid adult participants aged (50.7±10.0)years were recruited according to the inclusion and exclusion criteria, with 7 756 males and 3 911 females. The proportion of males, body mass index, systolic blood pressure, glycated hemoglobin A1c, fasting plasma glucose, triglyceride, hemoglobin, alanine aminotransferase and FT3 levels in HOMA2 IR-CP>2.18 group were significantly higher than those in HOMA2 IR-CP≤2.18 group (all P<0.05). The levels of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and free thyroxine in HOMA2 IR-CP>2.18 group were lower than those in HOMA2 IR-CP≤2.18 group (all P<0.001). Univariate Pearson correlation analysis showed that FT3 was associated with HOMA2 IR-CP (r=0.21, P<0.001). Multivariate logistic regression analysis suggested an association between FT3 and HOMA2 IR-CP after adjusting for confounding factors(Pfor trend<0.001). Subgroup analysis showed an association between FT3 and HOMA2 IR-CP in different subgroups of gender, age and glucose metabolism status (Pfor trend<0.05). Multiplication interaction analysis suggested that there was an interaction between FT3 and age (Pinteraction<0.001). Restricted cubic spline model analysis demonstrated that the correlation between FT3 and HOMA2 IR-CP was linear (Poverall<0.001, Pnonlinear=0.479). Conclusions: There is a correlation between serum FT3 and HOMA2 IR-CP in euthyroid adults. With the increase of FT3 level, insulin resistance increases gradually.

Sex-specific associations between the developmental alterations in the pituitary-thyroid hormone axis and thyroid nodules in Chinese euthyroid adults: a community-based cross-sectional study.

Previous studies have revealed the sex-specific features of pituitary-thyroid hormone (TH) actions and the prevalence of thyroid nodules (TNs) in children and adolescents. However, it was unclear in adults. We aimed to investigate the features of pituitary-TH actions in women and men at different ages, and the associations of thyrotropin (TSH), THs, and central sensitivity to THs indices including the thyroid feedback quantile-based index by FT4 (TFQIFT4) and the thyroid feedback quantile-based index by FT3(TFQIFT3) with of TNs in Chinese euthyroid adults. 8771 euthyroid adults from the communities in China were involved. Demographic, behavioral, and anthropometric data were gathered through the questionnaires. Ultrasound was performed to evaluate the TNs. TSH and THs levels were measured. The multivariable logistic regression and multivariable ordinal logistic regression were conducted. TFQIFT3 among both genders, except women aged 43 to 59 years, where it increased slightly. Additionally, there was an age-related decline in TFQIFT4 levels in both women and men at ages < 50 and < 53, respectively, but a marked increase after that. Lower TSH levels were significantly associated with a higher prevalence and lower odds of having fewer TNs using multiple nodules as the base category in both men and women (both P for trend < 0.05). Additionally, lower TFQIFT3 and TFQIFT4 levels were significantly associated with a higher prevalence of TNs in women (both P for trend < 0.05), and lower TFQIFT3 levels were significantly associated with a higher prevalence of TNs in men. Both higher TFQIFT3 and TFQIFT4 levels were significantly associated with higher odds of having fewer TNs using multiple nodules as the base category in women. However, the relationships between TFQIFT4 and the prevalence or number of TNs in men were not found. The trends of THs, TSH, TFQIFT4, and TFQIFT3 at different ages were sex-dependent. Both TFQIFT4 and TFQIFT3 levels were negatively associated with the prevalence and number of TNs in women. The present results may lead to a better understanding of the sex-specific relationships between the development of the pituitary-TH axis and the formation of TNs.

Free triiodothyronine to free thyroxine ratio as a marker of poor prognosis in euthyroid patients with acute coronary syndrome and diabetes after percutaneous coronary intervention.

In recent years, the free triiodothyronine/free thyroxine (FT3/FT4) ratio, a new comprehensive index for evaluating thyroid function, which could reflect thyroid function more stably and truly than serum thyroid hormone level, has been demonstrated to correlate with the risks of diabetes and cardiovascular disease in euthyroid adults. However, the correlation between thyroid hormone sensitivity and long-term prognosis in euthyroid patients with acute coronary syndrome (ACS) and diabetes after percutaneous coronary intervention (PCI) remains unclear. A total of 1,786 euthyroid patients with ACS who successfully underwent PCI at Beijing Anzhen Hospital from August 2021 to April 2022 were included in our study, which was divided into three groups according to tertiles of thyroid hormone sensitivity index. Cox regression, Kaplan-Meier, and receiver operating characteristic analyses were applied to analyze the associations between the FT3/FT4 ratio with ACS and diabetes after PCI. Our analysis indicated that a lower level of FT3/FT4 ratio in euthyroid patients with acute coronary syndrome (ACS) and diabetes after PCI showed significantly higher incidences of major adverse cardiac and cerebrovascular events (MACCE) when compared with a higher level of FT3/FT4 ratio. After adjusting for other covariates, patients with a lower level of FT3/FT4 ratio were negatively associated with the risk of MACCE than those with a higher level of FT3/FT4 ratio (adjusted OR =1.61, 95% CI 1.05-2.47, P = 0.028). In subgroup analyses, individuals were stratified by age, sex, BMI, ACS type, hypertension, and dyslipidemia, showing that there were no significant interactions between the FT3/FT4 ratio and all subgroups for MACCE. In addition, the FT3/FT4 ratio performed better on ROC analyses for cardiac death prediction [area under the curve (AUC), 0.738]. A reduced level of FT3/FT4 ratio was a potential marker of poor prognosis in euthyroid patients with ACS and diabetes after PCI.

Associations of thyroid feedback quantile-based index with diabetes in euthyroid adults in the United States and China

Background We aimed to investigate the associations between thyroid hormone sensitivity indices and diabetes in euthyroid adults in the United States and China. Methods 2296 euthyroid adults from the NHANES in the United States and 8319 euthyroid adults from the SPEED-Shunde in China were involved. The thyroid sensitivity indices, namely TFQIFT4 and TFQIFT3, were calculated. Multivariable logistic regression, restricted cubic spline analysis, and general ordinal logit regression were utilized. Results In the NHANES, compared with participants in quartile 1st (Q1), those in Q4 of TFQIFT3 (OR 2.12, 95% CI (1.18, 3.81)) and those in Q3 of TFQIFT4 (OR 2.31, 95% CI (1.18, 4.53)) (both P for trend < 0.05) were associated with a greater prevalence of diabetes. In the SPEED-Shunde, compared with participants in Q1, those in Q4 of TFQIFT3 had a greater prevalence of diabetes (OR 1.36, 95% CI (1.11, 1.66) (P for trend < 0.05), while no significant associations between TFQIFT4 and diabetes were found. Conclusions TFQIFT3 was associated with a higher prevalence of diabetes both in the United States and China. However, TFQIFT4 was only associated with a higher prevalence of diabetes in the United States, not in China. Further prospective cohort studies are necessary to validate these findings.

Impaired sensitivity to thyroid hormones is associated with albuminuria in the euthyroid population: results from NHANES.

The relationship between thyroid hormone sensitivity and albuminuria remains unclear. We aimed to investigate the association between thyroid hormone sensitivity and the risk of albuminuria in a euthyroid population. This cross-sectional study included 7634 euthyroid adults collected from the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2012. Central sensitivity to thyroid hormones was evaluated using the thyroid-stimulating hormone index (TSHI), the thyrotrophic thyroxine resistance index (TT4RI), and the thyroid feedback quantile-based index (TFQI). Peripheral sensitivity to thyroid hormones was measured using the free triiodothyronine/free thyroxine (FT3/FT4) ratio. Furthermore, the independent relationship between sensitivity to thyroid hormones and albuminuria was assessed. The proportion of albuminuria increased with a higher interquartile range of TFQI levels (7.31% vs. 7.89% vs. 7.95% vs. 9.89%, P = 0.024). Furthermore, TFQI was found to be independently associated with the risk of albuminuria after adjusting for confounding factors (OR = 1.28, 95% CI 1.01-1.60, P = 0.037). Subgroup analysis revealed a significant relationship between TFQI and albuminuria, especially among individuals over 60. In euthyroid subjects, impaired central sensitivity to thyroid hormones is associated with albuminuria. TFQI holds significant potential as an epidemiological tool for quantifying the impact of impaired central sensitivity on the risk of albuminuria.

Association of sensitivity to thyroid hormones with all-cause mortality in euthyroid US adults: A nationwide cohort study.

Background This study aimed to examine the associations of thyroid hormone sensitivity indices, including free triiodothyronine to free thyroxine (FT3/FT4) ratio, thyroid feedback quantile-based index by FT4 (TFQIFT4), thyroid-stimulating hormone index (TSHI), and thyrotrophic thyroxine resistance index (TT4RI) with all-cause mortality in euthyroid adults. Methods The study included 6243 euthyroid adults from the National Health and Nutrition Examination Survey (NHANES) 2007-2012. FT3/FT4 ratio, TFQIFT4, TSHI, and TT4RI were calculated. The multivariable Cox proportional hazard regression, restricted cubic spline (RCS), and subgroup analysis were conducted. Results Individuals in quartile 4th (Q4) had lower all-cause mortality than those in quartile 1st (Q1) of FT3/FT4 ratio (OR 0.70, 95% CI (0.51, 0.94)). Regarding TFQIFT4, individuals in Q4 of TFQIFT4 had a 43% higher all-cause mortality than those in Q1 (OR 1.43, 95% CI (1.05, 1.96)) (P <0.05, all). Compared with participants in Q1, no associations of TSHI and TT4RI with mortality were found. TFQIFT4 was linearly and positively associated with mortality. However, the FT3/FT4 ratio showed a U-shaped association with mortality. Conclusions Increased risk for all-cause mortality was positively associated with TFQIFT4, suggesting that increased risk for all-cause mortality was associated with decreased central sensitivity to thyroid hormones. Furthermore, the FT3/FT4 ratio showed a U-shaped association with mortality, with an inflection point at 0.5. However, more cohort studies are needed to validate the conclusions.

Associations between sensitivity to thyroid hormones and insulin resistance in euthyroid adults with obesity.

Impaired sensitivity to thyroid hormones (TH) was associated with metabolic syndrome. The study aimed to explore the association between central TH sensitivity indices and insulin resistance (IR) in euthyroid adults with obesity. This cross-sectional study enrolled 293 euthyroid outpatients with obesity in Beijing Chao-Yang Hospital. We used the thyroid feedback quantile-based index (TFQI), thyroid stimulating hormone index (TSHI), and thyrotrophic T4 resistance index (TT4RI) to indicate central TH sensitivity. IR was assessed by homeostasis model assessment of insulin resistance (HOMA-IR), hepatic insulin resistance index (hepatic-IR), the Matsuda index, and the adipose tissue insulin resistance index (Adipo-IR). Participants were categorized according to tertiles of TH sensitivity indices. We used multiple linear regressions to explore the associations. There was a significant stepwise increase in HOMA-IR and Adipo-IR from the lowest to the highest tertiles of TH sensitivity indices (all P<0.05). After adjustment for age, sex, body mass index, hypertension, hyperlipidemia, and diabetes, only Adipo-IR was significantly associated with TH sensitivity indices. On average, each unit increased in TFQI, TSHI, and TT4RI was associated with 1.19 (P=0.053), 1.16 (P=0.04), and 1.01 (P=0.03) units increased in Adipo-IR, respectively. There was no significant association between TH sensitivity indices and HOMA-IR, hepatic-IR, and the Matsuda index after adjustment for other risk factors. Reduced central TH sensitivity was associated with increased adipose tissue insulin resistance in euthyroid adults with obesity. The results further confirmed the importance of TH sensitivity on metabolic diseases.

Association of Hypervitaminosis D with Thyroid Function in Euthyroid Adult Patients

Aim: No study has investigated the effect of hypervitaminosis D on thyroid function. We aimed to analyze&#x0D; possible associations of hypervitaminosis D with thyroid function in levothyroxine-naive euthyroid&#x0D; patients.&#x0D; Material and Methods: Levothyroxine-naive euthyroid patients (&gt;18-year-old) with 25(OH) vitamin D&#x0D; level of ≥88 ng/mL after supplementation were analyzed retrospectively. We grouped them as: Group 1,&#x0D; TSH increased above the range; Group 2, TSH increased but in normal range; Group 3, TSH decreased&#x0D; but in normal range; Group 4, TSH decreased below the range; Group A, TSH increased; and Group&#x0D; B, TSH decreased. Before/after levels of TSH, fT4, Ca, P, creatinine, and TSH-change, fT4-change,&#x0D; 25(OH) vitamin D (basal/post-treatment and change), basal AntiTPO levels, and vitamin D dose were&#x0D; analyzed.&#x0D; Results: TSH-change -0.19±1.03 mIU/L and fT4-change 0.015±0.17 ng/dL were insignificant in&#x0D; total(n=64). Post-treatment 25(OH) vitamin D, TSH-after, and TSH-change were higher in group 1(n=3)&#x0D; than in group 2(n=22), group 3(n=33), or group 4(n=6) (p

Sex-Specific Associations of Five Serum Essential Metal Elements with Thyroid Nodules in Euthyroid Adults: a Cross‑sectional Study.

The association between the serum essential metal elements (magnesium, iron, copper, zinc, and calcium) and thyroid nodules is still inconsistent. The current study aims to investigate the relationship of metal elements with thyroid nodules and their malignant tendency. A total of 6480 Chinese euthyroid adults were included in our study. We collect basic information through questionnaires and medical checkups. We diagnose thyroid nodules by ultrasound and detect serum trace metal concentrations by using an automatic biochemical analyzer. Binary and multinomial logistic regressions were used to investigate the associations. As a result, we found that serum copper concentrations were positively associated with thyroid nodules in the second, third, and fourth quartiles, compared to the first quartile (P = 0.024, P = 0.016, P = 0.032) in women and P for trend is 0.038. There is a significant sex-specific association between copper concentrations and thyroid nodules (P for interaction = 0.009). The results of the multinomial logistic regression analyses indicate high serum calcium and magnesium concentrations emerged as consistent risk factors for thyroid nodules in both genders, whereas low zinc was a sex-specific factor. We also observed significant sex interactions in the relationships of magnesium (P for interaction = 0.043) with thyroid nodules with malignant tendency among participants with thyroid nodules. In conclusion, our study suggests that gender is an important factor when studying the association between serum metals and thyroid nodules. The imbalance of selected metal elements (calcium, copper, zinc, and magnesium) may relate to thyroid nodules and their malignant tendency, and future prospective studies are needed to further confirm the associations.

Low levels of free triiodothyronine are associated with risk of cognitive impairment in older euthyroid adults

Accumulated evidence showed that thyroid diseases induced cognitive decline. However, the relationship between thyroid hormones (THs) and cognition in older euthyroid people is still unclear. Our study aimed to estimate the association between THs within the euthyroid range and cognition in community-dwelling older adults in China. Data were extracted from a cohort study on the health status of rural older adults from the Guizhou province in China (HSRO). Serum thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) were measured using the electrochemiluminescence immunoassay. Cognitive function was evaluated by the Mini-Mental State Examination (MMSE). Linear regression and a binary logistic regression model were used to explore the relationship between THs and cognition in euthyroidism (TSH level of 0.27 ~ 4.20mIU/L). A total of 957 euthyroidism individuals were included in this study, with a mean (SD) age of 71.34 (6.35) years. In individuals with euthyroidism, serum TSH and FT3 levels were positively associated with cognition (TSH:β = 0.06, 95% CI 0.01 ~ 0.11, P = 0.03; FT3:β = 0.07, 95% CI 0.01 ~ 0.12, P = 0.01); and serum FT3 and TSH levels were significantly associated with cognitive domains (P < 0.05). Further, euthyroid individuals in the lowest serum FT3(OR = 1.96; 95% CI 1.27 ~ 3.03) quartile had a twofold increased risk of cognitive impairment compared to those in the highest quartile after adjusting for potential confounding factors. These findings suggested that low levels of FT3 could be an independent risk factor for cognitive impairment in older euthyroid adults. Additionally, a positive linear association exists between serum FT3 levels and cognitive domains (such as immediate memory, language, and attention). Further studies are needed to determine the underlying mechanisms and the community significance of these findings.

Vitamin D Deficiency Is Associated with Impaired Sensitivity to Thyroid Hormones in Euthyroid Adults.

The relationship between vitamin D deficiency and sensitivity to thyroid hormones was unclear. We aimed to explore the association of 25-hydroxyvitamin D (25(OH)D) levels with thyroid hormone sensitivity in euthyroid adults. A total of 3143 subjects were included. The serum 25(OH)D, free thyroxine (FT3), free thyrotropin (FT4), thyroid-stimulating hormone (TSH), and other clinical variables were measured. Vitamin D deficiency was defined as 25(OH)D < 20 ng/mL. Thyroid feedback quantile-based index (TFQI), parametric thyroid feedback quantile-based index (PTFQI), thyroid-stimulating hormone index (TSHI), thyrotrophic thyroxine resistance index (TT4RI), and FT3/FT4 were calculated to assess thyroid hormone sensitivity. Results showed that 58.8% of the participants had vitamin D deficiency. They had significantly higher levels of triglyceride, insulin, FT3, FT4, TSH, TFQI, PTFQI, TSHI, and TT4RI and lower levels of high-density lipoprotein cholesterol than those with sufficient vitamin D (all p < 0.05). Logistic regression analysis showed that the risk of impaired sensitivity to thyroid hormones evaluated by TFIQ, PTFQI, TSHI, and TT4RI increased by 68% (OR: 1.68; 95%CI: 1.45-1.95; and p < 0.001), 70% (OR: 1.70; 95%CI: 1.46-1.97; and p < 0.001), 66% (OR: 1.66; 95%CI: 1.43-1.92; and p < 0.001), and 50% (OR: 1.50; 95%CI: 1.30-1.74; and p < 0.001), respectively, in participants with vitamin D deficiency compared with those with sufficient vitamin D after adjusting for multiple confounders. In conclusion, in euthyroid populations, vitamin D deficiency was associated with impaired sensitivity to thyroid hormones.

Association between lifestyle factors and thyroid function in young sedentary euthyroid adults

PurposeThe present work examines the associations of dietary habits, sedentarism, physical activity (PA) levels and sleep habits, with thyroid function in young euthyroid adults. MethodsA total of 105 young euthyroid adults participated in this cross-sectional study. Thyroid function was determined in fasting conditions (> 6 h). Dietary habits were measured by a food frequency questionnaire and three non-consecutive 24 h recalls, and different dietary intake and patterns were then estimated. The time spent in sedentary, PA levels and sleep habits were objectively measured using a wrist-worn accelerometer. ResultsEnergy and carbohydrate intake were positively associated with thyroid stimulating hormone (TSH) (β = 0.222; R2 = 0.102; P = 0.022 and β = 0.425; R2 = 0.129; P = 0.007, respectively) whereas fat intake was negatively associated with TSH (β = −0.428; R2 = 0.137; P = 0.004). Energy intake was also positively associated with free triiodothyronine (β = 0.277; R2 = 0.137; P = 0.004). Further, adherence to the Mediterranean diet was negatively related to TSH and free thyroxine (FT4) (β = −0.221; R2 = 0.113; P = 0.020 and β = −0.268; R2 = 0.071; P = 0.007, respectively). Vigorous-intensity and overall PA were negatively associated with FT4 (β = −0.227; R2 = 0.052; P = 0.022 and β = −0.204; R2 = 0.042; P = 0.041, respectively). In contrast, no associations were found between sleep parameters and thyroid function. ConclusionsLifestyle factors such as dietary intake and PA levels seems to be related to thyroid function even in young euthyroid adults.

284-LB: From Metabolically Healthy Obesity (MHO) to Metabolically Unhealthy Obesity (MUHO)—Decreased Thyroid Hormone Sensitivity

Background: To explore the difference of thyroid hormone sensitivity between metabolically healthy and metabolically unhealthy obesity patients and its influence on obesity phenotype. Methods: 10927 euthyroid adults were enrolled, 4 groups based on the presence/absence of metabolic disorders (MD) and BMI were divided: 1) NC (n=1441): no MD and 22≤BMI &amp;lt; 25Kg/m2. 2) NMu (n=3765): MD and 22≤BMI &amp;lt; 25Kg/m2. 3) MHO (n=148): obese with no MD (BMI≥28Kg/m2). 4) MuHO (n=1981): obese with MD (BMI≥28Kg/m2). MD was defined as meeting none of the following criteria: fasted blood glucose ≤6.1 mmol/L; triglycerides ≥1.7 mmol/L; high density lipoprotein (HDL) &amp;lt;1.0 mmol/L (male) and &amp;lt;1.3 mmol/L (female); elevated SBP (≥130 mmHg) or/and DBP (≥85 mmHg). Thyroid hormone central sensitivity indices were calculated by thyroid feedback quantile-based index (TFQI), TSH index (TSHI), Chinese-referenced parametric TFQI (PTFQI) and thyrotropin thyroxine resistance index (TT4RI). Peripheral thyroid hormone sensitivity was evaluated by FT3/FT4 ratio. Results: Compared with MHO group, TFQI, PTFQI and TT4RI elevated in MuHO group, and the trend still existed after adjusting for confounding factors. High FT3/FT4 ratio was an independent risk factor for MuHO (OR = 1.22, 95%CI: 1.13, 1.37, P&amp;lt;0.001). In euthyroid obese patients, decreased TFQI was a protective factor for MHO (OR=0.71, 95%CI 0.51, 0.83, P=0.036), while TSHI (OR= 1.27, 95%CI: 1.11, 1.38, P =0.027) and TT4RI (OR= 1.08, 95%CI: 1.03, 1.16, P =0.022) were significantly correlated with the occurrence of MuHO. Conclusions: Thyroid hormone sensitivity is impaired with elevated BMI. Impaired thyroid hormone sensitivity associated with the development of metabolically unhealthy obesity in patients with similar BMI. Keywords Metabolically Healthy Obesity, Thyroid Hormone Sensitivity Disclosure N. Zhang: None. G. Wang: None. Funding National Natural Science Foundation of China (81770792)

Association between thyroid function and obesity phenotypes in healthy euthyroid individuals: an investigation based on Tehran Thyroid Study

AimsWe investigated whether thyroid function could be associated with obesity phenotypes amongst euthyroid individuals.Materials and methodsA cross-sectional analysis was conducted among healthy, euthyroid subjects. The study participants were chosen from the Tehran Thyroid Study (TTS). We analyzed 2988 euthyroid adults and classified them into four obesity phenotype groups: metabolically healthy normal weight (MHNW), metabolically healthy obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy obese (MUO). The statistical differences between thyroid hormones between various obesity phenotypes according to age and sex was compared using analysis of covariance (ANCOVA).ResultsIt was found that MHNW participants had higher levels of FT4 when compared with metabolically healthy or unhealthy obese subjects (P < 0.001), even after adjustment for the confounding variables. No difference was observed in the levels of TSH (P = 0.260) among obesity phenotypes. In the subgroup analysis according to the age, a significant difference was observed in the level of FT4 only in subjects with age < 55 years (P = 0.001). However, analyzing men and women separately did not show a significant difference in the FT4 level among obesity phenotypes (P > 0.05).Conclusion“Metabolically abnormality” was independently related to low normal FT4 levels in overweight/obese euthyroid individuals. There is a need for further research to understand how low FT4 levels are linked to metabolically unhealthy states in euthyroid individuals.

Central Sensitivity to Free Triiodothyronine With MAFLD and Its Progression to Liver Fibrosis in Euthyroid Adults.

Impaired sensitivity to thyroid hormones has been demonstrated to be positively associated with the prevalence of metabolic disorders. However, the relationship between sensitivity to thyroid hormones and metabolic dysfunction-associated fatty liver disease (MAFLD) and liver fibrosis remained unclear. We aimed to determine the associations of thyroid hormone sensitivity indices with MAFLD and its progression to liver fibrosis in Chinese euthyroid adults. This community-based study included 7906 euthyroid adults. We calculated the thyroid sensitivity indices, including free triiodothyronine to free thyroxine (FT3/FT4) ratio, Thyroid Feedback Quantile-based Index by FT4 (TFQIFT4), and Thyroid Feedback Quantile-based Index by FT3 (TFQIFT3), indicating peripheral and central thyroid hormone sensitivity respectively. Liver steatosis and fibrosis were diagnosed by vibration-controlled transient elastography (VCTE). Multivariable logistic/linear regression and restricted cubic spline (RCS) analysis were conducted. Compared with participants in the first quartile (Q1), the prevalence of MAFLD was increased by 62% in the fourth quartile (Q4) of FT3/FT4 ratio (OR 1.62; 95% CI [1.38, 1.91]) and by 40% in Q4 of TFQIFT3 (OR 1.40; 95% CI [1.18, 1.65]) (both P < .05). No associations between TFQIFT4 and the prevalence of MAFLD were found. In addition, compared with participants in Q1, the prevalence of liver fibrosis was increased by 45% in Q4 of TFQIFT3 (OR 1.45; 95% CI [1.03, 2.06]) (P < .05) in participants with MAFLD. Impaired central sensitivity to FT3 was associated with MAFLD and its progression to liver fibrosis. More prospective and mechanism studies are warranted to confirm these conclusions.

Association between different metabolic phenotypes and the development of hypothyroidism: 9 years follow-up of Tehran thyroid study.

The association between metabolic phenotypes and thyroid function has not yet been established; therefore, this study examined whether different metabolic phenotypes are associated with the development of hypothyroidism. Study participants were selected from the Tehran Thyroid Study (TTS). A total of 3338 euthyroid adults were included and categorized into four obesity phenotype groups: metabolically healthy normal weight (MHNW), metabolically healthy obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy obese (MUO). The participants were assessed at baseline and during three follow-up studies at three-year intervals. Multiple logistic regression analysis was used to examine the relationship between metabolic phenotypes and the development of hypothyroidism. In the total population, the chi-square test was only significant (P=0.008) in 3rd year with a higher prevalence of hypothyroidism in the MUNW phenotype, followed by MHO, MUO, and MHNW. Moreover, in the 3rd and 9th years of follow-up, hypothyroidism was more prevalent in MUO only in male subjects (P=0.002 and 0.035, respectively). In the unadjusted model, the MHO phenotype increased the odds of hypothyroidism compared with the MHNW phenotype (OR=1.51; 95% CI=1.04, 2.18; P-value=0.031). After adjusting for confounding factors, the odds of hypothyroidism were higher in the MUNW (OR=1.86; 95% CI=1.17, 2.96; P-value=0.008), MHO (OR=1.71; 95% CI=1.09, 2.67; P-value=0.018), and MUO (OR=1.64; 95% CI=1.03, 2.62; P-value=0.036) phenotypes than in the MHNW group. The MUNW phenotype increased the risk of hypothyroidism compared to MHNW, only in males. However, in females, the MHO phenotype increased the risk of hypothyroidism compared to MHNW. Both obesity and metabolic abnormalities are associated with hyperthyroidism. Healthy metabolic and weight maintenance were associated with a lower risk of hypothyroidism in males and females.