Impaired sensitivity to thyroid hormones is associated with hyperuricemia in a Chinese euthyroid population

Changes in Central Sensitivity to Thyroid Hormones vs. Urine Iodine during Pregnancy

INTRODUCTION/AIM

Central sensitivity to thyroid hormones refers to the responsiveness of the hypothalamic-pituitary-thyroid (HPT) axis to changes in circulating free thyroxine (fT4). Although dose-response relationships between thyroid hormones per se and urinary iodine (UI) levels have been observed, central sensitivity to thyroid hormones in relation to UI remains unexplored. The aim of the present study was to evaluate central sensitivity to thyroid hormones (by means of the Thyroid Feedback Quantile-based Index [TFQI], which is a calculated measure, based on TSH and fT4, that estimates central sensitivity to thyroid hormones) in pregnancy and to assess whether it differs according to gestational age and/or iodine intake.

MATERIALS AND METHODS

One thousand, one hundred and two blood and urine samples were collected from pregnant women (with a mean age ± SD of 30.4 ± 4.6 years) during singleton pregnancies; women with known/diagnosed thyroid disease were excluded. Specifically, TSH and fT4, anti-thyroid peroxidase antibodies and UI were measured in each trimester and at two months postpartum, while the TFQI was calculated for all the study samples. After the elimination of outliers, statistical analysis was conducted with analysis of variance (ANOVA) for the variables versus time period, while Pearson's correlation was used to assess the TFQI versus UI.

RESULTS

The mean TFQI index ranged from -0.060 (second trimester) to -0.053 (two months postpartum), while the corresponding UI was 137 and 165 μg/L, respectively. The TFQI-UI correlation was marginally negative (Pearson r: -0.323, p: 0.04) and significantly positive (r: +0.368, p: 0.050) for UI values over 250 μg/L, in the first and the second trimesters of pregnancy, respectively.

DISCUSSION

The TFQI is a new index reflecting central sensitivity to thyroid hormones. A lower TFQI indicates higher sensitivity to thyroid hormones. In our sample, the TFQI was mainly positively related to iodine intake in the second trimester of pregnancy (following the critical period of organogenesis). Thus, the observed changes in the TFQI may reflect the different ways of the central action of thyroid hormones, according to the phase of pregnancy. These results have the potential to enhance our comprehension of the changes in the HPT axis' function via variations in central sensitivity to thyroid hormones and its interplay with nutritional iodine status during pregnancy.

Effects of Insecticide and Herbicides on Thyroid Disturbances in Zebrafish

Thyroid cancer usually begins with thyroid dysfunction and nodules and has become the most common cancer globally, especially in women. Although the causes of thyroid dysfunction are complex, the presence of environmental pollutants, especially certain pesticides as established mutagens, has been widely accepted. Zebrafish (Danio rerio) have similar toxic reactions and signal transduction pathways to humans and are very similar to humans in physiology, development, and metabolic function. Here, the direct toxicity effects and mechanisms of different insecticides and herbicides on zebrafish thyroid functions and indirect toxicity effects originating from thyroid dysfunction were summarized and compared. The overall toxicity of insecticides on the zebrafish thyroid was greater than that of herbicides based on effective concentrations. Penpropathrin and atrazine were more typical thyroid disruptors than other pesticides. Meanwhile, chiral pesticides showed more sophisticated single/combined toxicity effects on both parental and offspring zebrafish. Besides thyroid hormone levels and HPT axis-related gene expression alteration, developmental toxicity, immunotoxicity, and oxidative damage effects were all observed. These data are necessary for understanding the thyroid interference effect of pesticides on humans and for screening for thyroid disruptors in surface water with zebrafish models for the pre-assessment of human health risks and ecological risk control in the future.

Uric Acid Status in Subclinical Hypothyroidism

Overt hypothyroidism is associated with high levels of serum uric acid (UA) however, the association between UA and thyroid function in patients with subclinical thyroid dysfunction remains unclear. Subclinical hypothyroidism (SCH) is a common endocrine disorder characterized by normal thyroxine (T4) and triiodothyronine (T3), and elevated thyroid stimulating hormone (TSH) levels, usually without clinical manifestations. Therefore, we carried out a study of patients with subclinical thyroid dysfunction to assess the relationship between thyroid function and UA. This lead us to review the literature to find to what extent subclinical hypothyroidism is associated with uric acid. This study adopts the method of retrospective analysis to collect general information and laboratory results aimed at assessing the correlation between uric acid and thyroid hormone levels. We searched 3 databases using different keywords. Literature search was done for articles published in the last ten years, between 2013-2023. All relevant studies were screened. A total of eighteen articles were finalized for the review. Some studies supported T3 supplementation resulting in SCH correction. Our study indicates that it is important to screen for serum uric acid levels routinely in patients with subclinical hypothyroidism.

Relationship between Thyroid Feedback Quantile-based Index and cardiovascular diseases in a population with normal thyroid function: Evidence from the National Health and Nutrition Examination Survey 2007-2012

BACKGROUND

Previous study has demonstrated a link between TFQI, indicating the central sensitivity of thyroid hormones, and conditions like obesity, diabetes, and metabolic syndrome.

HYPOTHESIS

Nevertheless, the potential relationship between TFQI and cardiovascular disease (CVD) in individuals with normal thyroid function has yet to be established.

METHODS

The present research is a retrospective cohort investigation that included a total of 6297 individuals who had normal function of the thyroid and no history of thyroid disorders. These participants were selected from National Health and Nutrition Examination Survey data set, covering the years 2007-2012. The calculation of TFQI was performed depending on FT4 and TSH. Given the complex survey design and sample weights, we used multivariate linear regression models and stratified analysis to evaluate TFQI's correlation with CVD.

RESULTS

Subjects with CVD had greater levels of TFQI than those with no CVD. After adjusting for other covariates, TFQI exhibited a positive association with CVD risk, and the OR was 1.706 (p = .005). In subgroup analyses that were stratified by sex and BMI, it was shown that female individuals who had CVD had greater levels of TFQI in comparison to female participants without CVD (p = .002). Furthermore, elevated levels of TFQI were consistently connected to a raised incidence of CVD in the BMI (>28 kg/m2) group after regulating for different covariates. Furthermore, correlation analysis showed an association between TFQI and metabolic biomarkers.

CONCLUSIONS

The levels of TFQI are strongly connected to the prevalence of CVD, indicating that energy metabolism may be related to the occurrence of CVD.

Identifying Risk Indicators of Cardiovascular Disease in Fasa Cohort Study (FACS): An Application of Generalized Linear Mixed-Model Tree

BACKGROUND

Today, cardiovascular disease (CVD) is the most important cause of death around the world. In this study, our main aim was to predict CVD using some of the most important indicators of this disease and present a tree-based statistical framework for detecting CVD patients according to these indicators.

METHODS

We used data from the baseline phase of the Fasa Cohort Study (FACS). The outcome variable was the presence of CVD. The ordinary Tree and generalized linear mixed models (GLMM) were fitted to the data and their predictive power for detecting CVD was compared with the obtained results from the GLMM tree. Statistical analysis was performed using the RStudio software.

RESULTS

Data of 9499 participants aged 35‒70 years were analyzed. The results of the multivariable mixed-effects logistic regression model revealed that participants' age, total cholesterol, marital status, smoking status, glucose, history of cardiac disease or myocardial infarction (MI) in first- and second-degree relatives, and presence of other diseases (like hypertension, depression, chronic headaches, and thyroid disease) were significantly related to the presence of CVD (P<0.05). Fitting the ordinary tree, GLMM, and GLMM tree resulted in area under the curve (AUC) values of 0.58 (0.56, 0.61), 0.81 (0.77, 0.84), and 0.80 (0.76, 0.83), respectively, among the study population. In addition, the tree model had the best specificity at 81% but the lowest sensitivity at 65% compared to the other models.

CONCLUSION

Given the superior performance of the GLMM tree compared with the standard tree and the lack of significant difference with the GLMM, using this model is suggested due to its simpler interpretation and fewer assumptions. Using updated statistical models for more accurate CVD prediction can result in more precise frameworks to aid in proactive patient detection planning.

Impaired Sensitivity to Thyroid Hormones Is Associated With Decreased Vitamin D Levels in the Euthyroid Population

CONTEXT

The relationship between vitamin D and thyroid profiles lacks consensus despite extensive investigations. Whether vitamin D levels correlate with thyroid hormone sensitivity remains largely unexplored.

OBJECTIVE

To explore the relationship between vitamin D levels and thyroid hormone sensitivity among euthyroid individuals.

METHODS

This study involved 6452 euthyroid participants. Clinical parameters, including TSH, free thyroxine, 25-hydroxyvitamin D [25(OH)D], and other relevant indicators were extracted from the National Health and Nutrition Examination Survey 2007-2012. To quantify thyroid hormone sensitivity, we calculated the Thyroid Feedback Quantile-based Index (TFQI), the TSH index (TSHI), and the thyrotropin thyroxine resistance index (TT4RI).

RESULTS

Subjects with impaired thyroid hormone sensitivity have decreased 25(OH)D levels (TFQI, TT4RI: P < 0.05; TSHI: P = .05574) following adjustment of confounding variables. Age-specific analysis found negative correlations between thyroid hormone sensitivity indices and 25(OH)D within the 20 to 60 years subgroup, turning positive in the 60 to 80 years subgroup. In females, thyroid hormone sensitivity indices and vitamin D levels were negatively linked, while in males, vitamin D's relationships with TFQI, TT4RI, and TSHI shifted from negative to positive when 25(OH)D levels exceeded 63.5 nmol/L, 56.7 nmol/L, and 56.7 nmol/L, respectively. Stratification by race revealed U-shaped curvilinear patterns resembling those found in the males. In body mass index (BMI) subanalysis, vitamin D had differing associations with thyroid hormone sensitivity indices: negative in the <25 kg/m2 and ≥30 kg/m2 subgroups and U-shaped in the 25-30 kg/m2 subgroup.

CONCLUSION

Impaired thyroid hormone sensitivity correlates with decreased vitamin D levels among euthyroid subjects, with associations varying by age, sex, race, and BMI.