Relationship between thyroid function and elevated blood pressure in euthyroid adults

Impaired sensitivity to thyroid hormones is associated with different grades of hypertension: A multicenter cross-sectional study

BACKGROUND AND AIM

Accumulating evidence suggests a potential link between thyroid function with hypertension. However, the research results are limited, and there is no research to explore the relationship between central and peripheral thyroid hormones (THs) sensitivity and different grades of hypertension in patients with coronary heart disease (CHD). This study aims to prove the complex interaction between thyroid system and blood pressure, and provides new ideas for the assessment of hypertension in patients with CHD.

METHODS AND RESULTS

Calculate parameters representing central and peripheral sensitivity to THs. Logistic regression analysis was used to analyze the relationship between central and peripheral THs sensitivity of CHD patients and different grades of hypertension, especially in different ages, sexes, blood glucose levels, smoking, and drinking statuses. Among the 34,310 participants, 19,610 (57.16 %) were diagnosed with hypertension. The risk of hypertension and TSHI (OR: 0.88; 95 % CI: 0.87-0.90; P < 0.001), TT4RI (OR: 0.998; 95 % CI: 0.998-0.999; P < 0.001), TFQI (OR: 0.63; 95 % CI: 0.60-0.67; P < 0.001), PTFQI (OR: 0.63; 95 % CI: 0.59-0.67; P < 0.001) was negatively associated. The risk of hypertension was positively associated with FT3/FT4 (OR: 1.20; 95 % CI: 1.17-1.22; P < 0.001). After stratified analysis, these associations remained significant at different ages, sexes, blood glucose levels, grades of hypertension, smoking, and drinking statuses (P < 0.001).

CONCLUSIONS

This study shows that the decrease in central THs sensitivity index and the increase in peripheral THs sensitivity index are associated with a higher risk of hypertension in CHD patients.

An endothelial regulatory module links blood pressure regulation with elite athletic performance

The control of transcription is crucial for homeostasis in mammals. A previous selective sweep analysis of horse racing performance revealed a 19.6 kb candidate regulatory region 50 kb downstream of the Endothelin3 (EDN3) gene. Here, the region was narrowed to a 5.5 kb span of 14 SNVs, with elite and sub-elite haplotypes analyzed for association to racing performance, blood pressure and plasma levels of EDN3 in Coldblooded trotters and Standardbreds. Comparative analysis of human HiCap data identified the span as an enhancer cluster active in endothelial cells, interacting with genes relevant to blood pressure regulation. Coldblooded trotters with the sub-elite haplotype had significantly higher blood pressure compared to horses with the elite performing haplotype during exercise. Alleles within the elite haplotype were part of the standing variation in pre-domestication horses, and have risen in frequency during the era of breed development and selection. These results advance our understanding of the molecular genetics of athletic performance and vascular traits in both horses and humans.

Associations of TSH, free T3, free T4, and conversion ratio with incident hypertension: results from the prospective Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Objective

To evaluate the association of TSH, free T3 (FT3), free T4 (FT4), and conversion (FT3:FT4) ratio values with incident hypertension.

Materials and methods

The study included data from participants of the ELSA-Brasil study without baseline hypertension. Serum TSH, FT4 and FT3 levels, and FT3:FT4 ratio values were assessed at baseline, and incident hypertension (defined by blood pressure levels ≥ 140/90 mmHg) was estimated over a median of 8.2 years of follow-up. The risk of incident hypertension was evaluated considering a 1-unit increase in TSH, FT4, FT3, and conversion ratio values and after dividing these variables into quintiles for further analysis using Poisson regression with robust variance. The results are presented as relative risks (RR) and 95% confidence intervals (CIs) before and after adjustment for multiple variables.

Results

The primary analysis incorporated data from 5,915 euthyroid individuals, and the secondary analysis combined data from all euthyroid individuals, 587 individuals with subclinical hypothyroidism, and 31 individuals with subclinical hyperthyroidism. The rate of incident hypertension was 28% (95% CI: 27%-29.3%). The FT4 levels in the first quintile (0.18-1.06 ng/dL) were significantly associated with incident hypertension (RR: 1.03, 95% CI: 1.01-1.06) at follow-up. The association between FT4 levels in the first quintile and incident hypertension was also observed in the analysis of combined data from euthyroid individuals and participants with subclinical thyroid dysfunction (RR: 1.04, 95% CI: 1.01-1.07). The associations were predominantly observed with systolic blood pressure levels in euthyroid individuals. However, in the combined analysis incorporating euthyroid participants and individuals with subclinical thyroid dysfunction, the associations were more pronounced with diastolic blood pressure levels.

Conclusion

Low FT4 levels may be a mild risk factor for incident hypertension in euthyroid individuals and persons with subclinical thyroid dysfunction.

Thyroid-related Hormones and Hypertension Incidence in Middle-Aged and Older Hispanic/Latino Adults: The HCHS/SOL Study

Background

Thyroid-related hormones act to regulate metabolic pathways and blood pressure (BP). However, the relationship of TSH and peripheral thyroid hormones and the role of the hypothalamic-pituitary-thyroid axis on hypertension development is not fully understood. We assessed sex-specific associations of thyroid-related hormones with BP and hypertension in Hispanic/Latino adults followed for 6 years.

Methods

We studied 1789 adults, ages 45 to 74, free of diabetes at baseline from a subcohort of the Hispanic Community Health Study/Study of Latinos. We assessed TSH, free T4 (FT4), T3, and various indicators of thyroid axis. Using multivariable linear and Poisson regression adjusted for survey design and confounding variables, we estimated a priori sex-specific associations of thyroid-related hormones with changes in BP and hypertension development.

Results

In men and women, TSH and TSH/FT4 ratios were associated with changes in diastolic BP and T3 with changes in pulse pressure and the development of hypertension from prehypertension. In men, a 1-SD increase in TSH [incident rate ratio (IRR) = 1.42; 95% confidence interval (CI): 1.15, 1.75] and TSH/FT4 ratio (IRR = 1.20; 95% CI: 1.07, 1.35) were positively associated with the development of hypertension from prehypertension while the TSH/FT4 ratio (IRR = 0.85; 95% CI: .72, 1.00) was protective in women. We observed sex-specific differences in associations of the T3/FT4 ratio and indices of pituitary sensitivity to thyroid hormones with changes in pulse pressure and hypertension development.

Conclusion

Thyroid-related hormones are associated with sex-specific changes in BP and hypertension among Hispanic/Latino adults consistent with selected studies conducted in other populations. Mechanisms underlying associations of pituitary sensitivity to thyroid hormones with BP and hypertension development warrant further study.

Sensitivity to thyroid hormone and risk of components of metabolic syndrome in a Chinese euthyroid population

INTRODUCTION

To evaluate the association of sensitivity to thyroid hormone with metabolic syndrome (MetS) and its components in a Chinese euthyroid population.

METHODS

A total of 3573 participants from Pinggu Metabolic Disease Study were analyzed. Serum-free triiodothyronine (FT3), free thyroxine (FT4), thyrotropin (TSH), total adipose tissue (TAT), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) area of abdominal, and lumbar skeletal muscle area (SMA) were measured. Central thyroid hormone resistance was calculated by the Thyroid Feedback Quantile-based Index (TFQI) and Chinese-referenced Parametric TFQI (PTFQI), Thyrotroph T4 Resistance Index (TT4RI) and TSH Index (TSHI). Peripheral thyroid hormone resistance was assessed by FT3/FT4 ratio.

RESULTS

Higher values of TSHI (odds ratio [OR] = 1.167, 95% confidence interval [CI]: 1.079-1.262, p < .001), TT4RI (OR = 1.115, 95% CI: 1.031-1.206, p = .006), TFQI (OR = 1.196, 95% CI: 1.106-1.294, p < .001), PTFQI (OR = 1.194, 95% CI: 1.104-1.292, p < .001), and lower values of FT3/FT4 ratio (OR = 0.914, 95% CI: 0.845-0.990, p = .026) were associated with MetS. Increased levels of TFQI and PTFQI were associated with abdominal obesity, hypertriglyceridemia, and hypertension. Increased levels of TSHI and TT4RI were associated with hypertriglyceridemia, abdominal obesity, low high-density lipoprotein cholesterol. Reduced levels of FT3/FT4 ratio were associated with hyperglycemia, hypertension, and hypertriglyceridemia. The levels of TSHI, TFQI, and PTFQI were negatively related to SMA and positively related to VAT, SAT, and TAT (all p < .05).

CONCLUSIONS

Reduced thyroid hormone sensitivity was associated with MetS and its components. Impaired thyroid hormone sensitivity might affect the distribution of adipose tissue and muscle.

Gender differences in the prevalence and clinical correlates of thyroid dysfunction in patients with first-episode and drug-naïve major depressive disorder with comorbid suicide attempts: a large cross-sectional study

BACKGROUND

Gender differences in patients with major depressive disorder (MDD) are commonly reported; however, gender differences in first-episode and drug-naïve (FEDN) MDD patients with comorbid suicide attempts have not been reported. This study aimed to examine potential gender differences in the prevalence and clinical correlates of comorbid abnormal thyroid function (ATF) in FEDN MDD patients with comorbid suicide attempts.

METHODS

A cross-sectional study of 1718 FEDN MDD patients was conducted. The demographic and clinical data were collected. The Hamilton Depression Scale (HAMD), the Hamilton Anxiety Scale (HAMA) and Positive and Negative Syndrome Scale (PANSS) were used to assess depression, anxiety and psychotic symptoms, respectively. Thyroid function parameters and blood glucose levels were measured.

RESULTS

There was no gender difference in the prevalence of ATF between male (78.6%, 88/112) and female MDD patients (74.8%, 175/234) with comorbid suicide attempts. In the male and female subgroups, duration of disease, HAMD score, HAMA score, anti-thyroglobulin (TgAb), thyroid peroxidases antibody (TPOAb), diastolic blood pressure (DBP), systolic blood pressure (SBP), glucose level and the rate of psychotic symptoms were higher in patients with ATF than those without ATF in MDD with comorbid suicide attempt (all P < 0.05). There was a gender main effect only on SBP (F = 7.35, P = 0.007). Furthermore, binary logistic regression analysis showed that HAMD score, DBP and glucose levels were independently with ATF in both male and female MDD patients with comorbid suicide attempts. However, anxiety symptoms, psychotic symptoms and TPOAb levels were significantly associated with ATF only in female MDD patients with comorbid suicide attempts.

CONCLUSION

Our study showed no gender differences in the prevalence of ATF in FEDN MDD patients with comorbid suicide attempts. Depression, DBP and glucose levels were associated with ATF in both male and female MDD patients with comorbid suicide attempts, whereas anxiety, psychotic symptoms and TPOAb level were correlated with ATF only in female MDD patients with suicide attempts.

Circulating free T3 associates longitudinally with cardio-metabolic risk factors in euthyroid children with higher TSH

Introduction

Thyroid hormones play major roles in the regulation of body composition and metabolism, and therefore, the relationship between thyroid hormones and cardio-metabolic risk has been extensively studied in adults. In this study, we aimed to test whether free triiodothyronine (fT3) associates longitudinally with cardio-metabolic risk factors in euthyroid children.

Methods

A prospective study cohort of 599 apparently healthy school-age children were assessed at baseline (mean age 8.1 ± 2.1 years), of whom 270 children were also assessed at follow-up (4 years later). Circulating thyroid-stimulating hormone (TSH), free thyroxine (fT4), and fT3 were measured, and cardio-metabolic risk was assessed by means of body mass index (BMI), waist circumference, visceral fat (by ultrasound), blood pressure, circulating lipids, and homeostasis model assessment of insulin resistance (HOMA-IR) index, both at baseline and at follow-up.

Results

All studied children had normal thyroid function tests. Independent associations between baseline fT3 and both baseline and follow-up BMI, systolic blood pressure, mean arterial blood pressure, triglycerides, and HOMA-IR were found using multivariate regression analysis (adjusting for sex and baseline age and BMI). Analyses of effect sizes showed that for each 1 unit-increase in baseline fT3 (pg/ml), follow-up BMI-standard deviation score (SDS) increased by 0.31 units (z-score) and systolic blood pressure by 6.6 units (mmHg). The observed longitudinal associations were more robust in children belonging to the upper TSH tertile who showed higher TSH levels and were characterized by weighing more and having the highest fT3 levels. In these children, for each 1 unit-increase in baseline fT3 (pg/ml), follow-up BMI-SDS increased by 0.67 units (z-score) and systolic blood pressure by 10.2 units (mmHg).

Conclusions

Circulating fT3 associates longitudinally with cardio-metabolic risk factors in euthyroid children with higher TSH. The observed associations of thyroid hormones in these children could conceivably respond to a homeostatic attempt to reduce their cardio-metabolic risk.

Helicobacter pylori infection increase the risk of subclinical hyperthyroidism in middle-aged and elderly women independent of dietary factors: Results from the Tianjin chronic low-grade systemic inflammation and health cohort study in China

Background

Prospective studies on the association between Helicobacter pylori (H. pylori) infection and subclinical hyperthyroidism are limited. We, therefore, designed a large-scale cohort study to explore the association between H. pylori infection and the risk of subclinical hyperthyroidism in women.

Methods

This prospective cohort study investigated 2,713 participants. H. pylori infection was diagnosed with the carbon 13 breath test. Subclinical hyperthyroidism was defined as serum thyroid-stimulating hormone levels are low or undetectable but free thyroxine and tri-iodothyronine concentrations are normal. Propensity score matching (PSM) analyses and Cox proportional hazards regression models were used to estimate the association between H. pylori infection and subclinical hyperthyroidism.

Results

A total of 1,025 PS-matched pairs of H. pylori infection women were generated after PSM. During 6 years of follow-up, the incidence rate of subclinical hyperthyroidism was 7.35/1,000 person-years. After adjusting potential confounding factors (including iodine intake in food and three main dietary patterns score), the multivariable hazard ratio (HR; 95% confidence intervals) of subclinical hyperthyroidism by H. pylori infection was 2.49 (1.36, 4.56). Stratified analyses suggested a potential effect modification by age, the multivariable HR (95% confidence intervals) was 2.85 (1.45, 5.61) in participants aged ≥ 40 years and 0.70 (0.08, 6.00) in participants aged < 40 years (P for interaction = 0.048).

Conclusion

Our prospective study first indicates that H. pylori infection is significantly associated with the risk of subclinical hyperthyroidism independent of dietary factors among Chinese women, especially in middle-aged and older individuals.Clinical Trial Registration:https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000031137, identifier UMIN000027174.

Ultra-processed food consumption and risk of subclinical thyroid dysfunction：A prospective cohort study

Background: Prospective cohort studies linking Ultra-processed foods (UPF) and subclinical thyroid dysfunction (SCTD) are limited, especially in Chinese adults. Objective: We designed a large-scale cohort study to examine whether UPF...

Association between dietary onion intake and subclinical hypothyroidism in adults: a population-based study from an iodine-replete area

PURPOSE

The protective effect of onion against thyroid hypofunction has been reported in animal studies. However, in humans, the association between onion consumption and subclinical hypothyroidism (SCH) are unclear. The study sought to explore the association between habitual onion intake and SCH among adult population from an iodine-replete area.

METHODS

A cross-sectional study (6515 men and 5290 women) was performed in Tianjin, China. Frequency of onion consumption was assessed using a valid self-administered food frequency questionnaire. Serum free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) were determined by chemiluminescence immunoassay. SCH was diagnosed with TSH > 4.78 mIU/L. Multiple logistic regression was used to evaluate the association of onion intake with SCH.

RESULTS

The prevalence of SCH was 2.56% in men and 7.18% in women, respectively. In women, the fully adjusted odds ratios [95% confidence interval (CI)] of having SCH across increasing frequency of onion intake were 1.00 (reference) for <1 time/week, 0.99 (0.73, 1.34) for 1-3 times/week, 0.74 (0.53, 1.03) for 4-6 times/week, and 0.67 (0.47, 0.97) for ≥7 times/week (P for trend <0.01). However, we observed no significant association between onion intake and SCH in men. Stratified analyses suggested a potential effect modification by age: the odds ratios (95% CI) across extreme quartiles was 0.37 (0.17, 0.80) in <40 women and 1.11 (0.51, 2.47) in >60 women.

CONCLUSIONS

Frequent consumption of onion is inversely associated with SCH in adult women from an iodine-replete area. Further studies are needed to explore the casual relationship. TRIAL REGISTRATION WEBSITE: https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000031137.

Association of thyroid hormones with blood pressure and arterial stiffness in the general population: The Dali study

Thyroid dysfunction plays a role in blood pressure (BP) regulation. However, the associations between thyroid function and BP and arterial stiffness in the general Chinese population without thyroid disease are unknown. This population-based cross-sectional study aimed to investigate the association between thyroid function and peripheral and central BP and arterial stiffness in Chinese individuals. After excluding those who had thyroid diseases or incomplete clinical measurements, this study included 691 participants. Of the participants, 444 (64.2%) were women and 215 (31.1%) had hypertension. After adjustment for covariates, serum FT3 was significantly associated with a higher pulse rate in both sexes. In men, each 2.72-fold increase in serum FT4 levels was associated with higher peripheral systolic BP (+10.82 mmHg, p = .005) and pulse pressure (+5.71 mmHg, p = .03). Each 2.72-fold increase in serum FT4 levels was associated with higher central systolic BP (+8.03 mmHg, p = .03) and pulse pressure (+3.89 mmHg, p = .05). In women, serum FT4 was only associated with a higher central pulse pressure (+2.96 mmHg, p = .04). After adjustment for covariates, serum FT4 was significantly associated with a faster cfPWV exclusively in men. Our study showed that serum FT4 is associated with higher peripheral and central BP and faster cfPWV in men, whereas serum FT3 is positively associated with a higher pulse rate in both sexes, indicating that the effects of thyroid function on BP and arterial stiffness are more significant in men than in women.

The association between longitudinal trends of thyroid hormones levels and incident hypertension in a euthyroid population

Thyroid hormones, including free triiodothyronine (FT3), free thyroxine (FT4), have well-recognized effects on the cardiovascular system. However, the evidence is lacking regarding the relationship between repeated FT3, FT4, and thyroid-stimulating hormone (TSH) measurements and incident hypertension. The aim of this cohort study was to examine how longitudinal trends of serum FT3, FT4, and TSH levels are related to the development of hypertension in a euthyroid population. A prospective study (n = 5926) was performed in Tianjin, China. Participants without a history of hypertension were followed up for ~4 years (median: 3 years). Hypertension was defined according to the criteria of JNC7. FT3, FT4, and TSH were determined by chemiluminescence immunoassay methods. FT3, FT4, TSH, and blood pressure were assessed yearly during follow-up. Adjusted Cox proportional hazards regression models were used to assess the relationships between baseline, means, and annual changes in FT3, FT4, TSH, and hypertension. The incidence rate of hypertension per 1000 person-years was 73. Compared with the lowest quartile, the multivariable-adjusted hazards ratios (95% confidence interval) for hypertension in the highest quartiles of changes in FT3, FT4, and TSH were 1.51 (1.23-1.84), 2.04 (1.67-2.48), and 1.20 (0.99-1.45), respectively. Similar relationships were observed between the means of FT3, FT4, TSH, and hypertension. However, we found no correlations between baseline FT3, FT4, TSH, and incident hypertension. The present study is the first to demonstrate that the annual changes and means, but not baseline FT3 and FT4 values are independently related to the risk of incident hypertension in the euthyroid general population.

Relationship between excess iodine, thyroid function, blood pressure, and blood glucose level in adults, pregnant women, and lactating women: A cross-sectional study

High water iodine concentration in drinking water can lead to excessive iodine, which will affect normal thyroid function, blood glucose, and blood pressure, especially among pregnant and lactating women. The aim of the present study was to determine the relationship between iodine, thyroid function, blood pressure, and blood glucose level among adults, and pregnant and lactating women in areas that are iodine-adequate (IA) and iodine-excess (IE) with respect to iodine concentrations in drinking water. A cross-sectional survey was conducted involving 144 pregnant and 237 lactating women in Shanxi Province, and 828 adults in Shandong Province. Water iodine, urinary iodine, thyroid function, blood pressure, and blood glucose were measured. Compared with the IA area, the water iodine concentration (WIC) in the IE area was higher (adults, 325.00 µg/L vs. 71.40 µg/L; pregnant and lactating women, 464.80 µg/L vs. 57.50 µg/L). For adults, and pregnant and lactating women, in the IE area, the urinary iodine concentration (UIC), free thyroxine (FT₄ [except for lactating women]), and systolic blood pressure (only adults 18-40 years of age) were significantly higher, while the blood glucose level and the prevalence of hyperglycemia (except for adults) was lower, and the free triiodothyronine (FT₃), thyroid-stimulating hormone (TSH), thyroglobulin antibody (TgAb), thyroid peroxidase antibody (TPOAb), and hypertension-positive rates of the three populations were not significantly different. For adults, systolic and diastolic pressure were positively correlated with FT₃ and FT₄, respectively, while the blood glucose level were inversely associated with the WIC. For pregnant women, systolic pressure and the WIC, diastolic pressure and FT₄, blood glucose level and FT₃ were all positively correlated, while the blood glucose level was inversely associated with TSH, WIC and UIC. For lactating women, systolic pressure was positively correlated with WIC and UIC, while blood glucose level were inversely associated with WIC and UIC. Pregnant and lactating women in the IE area were at lower risk for an association with hyperglycemia. Collectively, our research showed that long-term exposure to high water iodine is a high-risk factor for abnormal blood pressure and a low-risk factor for abnormal blood glucose level, especially for special populations such as pregnant and lactating women. Moreover, enhanced monitoring of blood pressure and blood glucose level in people with abnormal thyroid function in areas with high water iodine is important.

The Association Between Serum Thyrotropin Within the Reference Range and Metabolic Syndrome in a Community-Based Chinese Population

PURPOSE

We aimed to ascertain the association between thyrotropin (TSH) levels in euthyroid state and the prevalence of metabolic syndrome (MetS) in a community-based Chinese population.

PARTICIPANTS AND METHODS

Based on a large and well-characterized community cohort in Beijing, China, 1831 men and 1742 women with serum TSH levels within the reference range (0.50-4.78 µIU/mL) were stratified by quartiles of TSH (Q1-4). MetS was identified according to the criteria of International Diabetes Federation guidelines. Poisson regression models were used to estimate the association between serum TSH and the prevalence of MetS and its components before and after adjustment for potential confounding factors. The reported association was measured using the prevalence ratio (PR) with its respective 95% confidence interval (95% CI).

RESULTS

The prevalence of MetS in euthyroid population across TSH quartiles (Q1-4) was 38.9%, 44.6%, 41.0%, and 47.7%, respectively, in men (P = 0.045), and 47.7%, 46.6%, 46.9%, and 54.6%, respectively, in women (P = 0.032). Compared with the reference group TSH-Q1, the prevalence of MetS was higher among TSH-Q4 group both in men (PR = 1.27; 95% CI: 1.09, 1.48, P = 0.002) and women (PR = 1.21; 95% CI: 1.07, 1.37, P = 0.003) even after adjustment for age, lifestyle factors, serum levels of free triiodothyronine (FT3), and free thyroxine (FT4). Most of the components of MetS were common in higher serum TSH levels within the normal range.

CONCLUSION

The prevalence of MetS and most of its components increased in the higher TSH group in euthyroid Chinese population.

Low-Normal Thyroid Function Predicts Incident Anemia in the General Population With Euthyroid Status

CONTEXT

Thyroid hormones (THs) have direct and indirect effects on hematopoiesis. However, few studies have directly evaluated the effect of THs on incident anemia among euthyroid subjects. This cohort study aimed to explore whether THs under physiological conditions can affect the development of anemia in the general population.

DESIGN

A total of 12,310 participants were enrolled in the cohort study (∼5-year follow-up period; mean, 3.1 years). A chemiluminescence immunoassay was used to measure free T3 (FT3), free T4 (FT4), and TSH, and anemia was defined according to the World Health Organization recommendation. THs, TSH, and Hb were assessed yearly during follow-up. Multivariable Cox proportional hazards regression models were used to assess the association between THs, TSH, and incident anemia.

RESULTS

The fully adjusted hazards ratios (95% CI) of anemia per 1-unit change in FT3, FT4, and TSH concentrations were 0.70 (0.56, 0.87), 0.93 (0.88, 0.98), and 1.19 (0.94, 1.50) (P < 0.01, P < 0.01, and P = 0.14, respectively). Moreover, a significant and positive association between FT3, FT4, and annual changes in Hb (standard regression coefficients of 0.056 and 0.028, respectively; both P < 0.01) was observed. Similar associations were observed when the participants who had thyroid dysfunction upon follow-up were excluded.

CONCLUSIONS

The current study demonstrated that THs significantly predict future anemia and annual changes in Hb, even in the euthyroid population.

Triiodothyronine Reduces Vascular Dysfunction Associated with Hypertension by Attenuating Protein Kinase G/Vasodilator-Stimulated Phosphoprotein Signaling

Vascular dysfunction associated with hypertension comprises hypercontractility and impaired vasodilation. We have previously demonstrated that triiodothyronine (T3), the active form of thyroid hormone, has vasodilatory effects acting through rapid onset mechanisms. In the present study, we examined whether T3 mitigates vascular dysfunction associated with hypertension. To test the direct effects of T3 in hypertensive vessels, aortas from female Dahl salt-sensitive (Dahl SS) rats fed a high-salt diet (8% NaCl, HS group) and their age-matched controls fed a standard low-salt diet (0.3% NaCl, LS group) for 16 weeks were isolated and used in ex vivo vascular reactivity studies. We confirmed that the HS group exhibited a higher systolic blood pressure in comparison with the control LS group and displayed aortic remodeling. Aortas from both groups were pretreated with T3 (0.1 μM) for 30 minutes at 37°C in a 5% CO₂ incubator before functional vascular studies. T3 treatment significantly attenuated hypercontractility and improved impaired endothelium-dependent vasodilation in aortas from the HS group. These vascular improvements in response to T3 were accompanied by increased phosphorylation of vasodilator-stimulated phosphoprotein (VASP) at serine 239, a vasodilatory factor of the cGMP-dependent protein kinase (PKG)/VASP signaling pathway in vascular smooth muscle cells. Moreover, increased production of reactive oxygen species in aortas from the HS group were significantly reduced by T3, suggesting a potential antioxidant effect of T3 in the vasculature. These results demonstrate that T3 can mitigate hypertension-related vascular dysfunction through the VASP signaling pathway and by reducing vascular ROS production. SIGNIFICANCE STATEMENT: This study demonstrates that triiodothyronine (T3) directly acts on vascular tone and has a beneficial effect in hypertension-induced vascular dysfunction. T3 augmented vasodilation and diminished vasoconstriction in blood vessels from hypertensive rats in association with activation of the protein kinase G/vasodilator-stimulated phosphoprotein signaling pathway that activates vascular relaxation and exerted an antioxidant effect. Collectively, these results show that T3 is a potential vasoprotective agent with rapid action on hypertension-related vascular dysfunction.