High serum thyrotropin levels are associated with current but not with incident hypertension

Hypopituitarism and Cardiovascular Risk

Hypopituitarism, resulting from a partial or complete deficiency of anterior or posterior pituitary hormones, is associated with increased cardiovascular (CV) morbidity and mortality. This heterogeneous endocrinological disorder may arise from various etiologies, including genetic mutations, pituitary tumors, traumatic brain injury, and autoimmune diseases. Hypopituitarism often results in multiple endocrine deficits that contribute to metabolic dysregulation characterized by insulin resistance, dyslipidemia, and increased visceral adiposity, all known risk factors for CV disease (CVD). Additionally, the presence of chronic inflammation and endothelial dysfunction further increases the risk of CVD in these patients. While standard hormone replacement therapy (HRT) is crucial for restoring hormonal balance, it can sometimes have adverse metabolic effects that can exacerbate atherosclerosis and CVD. Emerging evidence suggests that optimizing HRT regimens and addressing specific hormone deficiencies, such as growth hormone and cortisol, may reduce these risks and improve CV outcomes. This review comprehensively analyzes the etiology, pathophysiological mechanisms underlying CV risk in anterior pituitary dysfunction, and treatment strategies to mitigate CV morbidity and mortality in patients with hypopituitarism.

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.

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.

The Positive Association between Subclinical Hypothyroidism and Newly-Diagnosed Hypertension Is More Explicit in Female Individuals Younger than 65

BACKGROUND

Subclinical hypothyroidism (SCH) is the most common thyroid dysfunction, and its relationship with blood pressure (BP) has been controversial. The aim of the study was to analyze the association between SCH and newly-diagnosed hypertension.

METHODS

Based on data from the Thyroid disease, Iodine nutrition and Diabetes Epidemiology (TIDE) study, 49,433 euthyroid individuals and 7,719 SCH patients aged ≥18 years were enrolled. Patients with a history of hypertension or thyroid disease were excluded. SCH was determined by manufacturer reference range. Overall hypertension and stage 1 and 2 hypertension were diagnosed according to the guidelines issued by the American College of Cardiology/American Heart Association in 2017.

RESULTS

The prevalence of overall hypertension (48.7%), including stage 1 (28.9%) and 2 (19.8%) hypertension, increased significantly in SCH patients compared with euthyroid subjects. With elevated serum thyroid stimulating hormone (TSH) level, the hypertension prevalence also increased significantly from the euthyroid to different SCH subgroups, which was more profound in females or subjects aged <65 years. The age- and sex-specific regression analysis further demonstrated the same trends in the general population and in the 1:1 propensity matched population. Similarly, several BP components (i.e., systolic, diastolic, and mean arterial BP) were positively associated with TSH elevation, and regression analysis also confirmed that all BP components were closely related with SCH in female subjects aged <65 years.

CONCLUSION

The prevalence of hypertension increases for patients with SCH. SCH tends to be associated with hypertension and BP components in females younger than 65 years.

Noncanonical Thyroid Hormone Receptor α Action Mediates Arterial Vasodilation

CONTEXT

Hypothyroidism impairs cardiovascular health and contributes to endothelial dysfunction with reduced vasodilation. How 3,5,3'-triiodothyronine (T3) and its receptors are involved in the regulation of vasomotion is not yet fully understood. In general, thyroid hormone receptors (TRs) either influence gene expression (canonical action) or rapidly activate intracellular signaling pathways (noncanonical action).

OBJECTIVE

Here we aimed to characterize the T3 action underlying the mechanism of arterial vasodilation and blood pressure (BP) regulation.

METHODS

Mesenteric arteries were isolated from male rats, wild-type (WT) mice, TRα knockout (TRα 0) mice, and from knockin mice with a mutation in the DNA-binding domain (TRα GS). In this mutant, DNA binding and thus canonical action is abrogated while noncanonical signaling is preserved. In a wire myograph system, the isolated vessels were preconstricted with norepinephrine. The response to T3 was measured, and the resulting vasodilation (Δ force [mN]) was normalized to maximum contraction with norepinephrine and expressed as percentage vasodilation after maximal preconstriction with norepinephrine (%NE). Isolated vessels were treated with T3 (1 × 10-15 to 1 × 10-5 mol/L) alone and in combination with the endothelial nitric oxide-synthase (eNOS) inhibitor L-NG-nitroarginine methyl ester (L-NAME) or the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin. The endothelium was removed to determine the contribution of T3 to endothelium-dependent vasodilation. The physiological relevance of T3-induced vasodilation was determined by in vivo arterial BP measurements in male and female mice.

RESULTS

T3 treatment induced vasodilation of mesenteric arteries from WT mice within 2 minutes (by 21.5 ± 1.7%NE). This effect was absent in arteries from TRα 0 mice (by 5.3 ± 0.6%NE, P < .001 vs WT) but preserved in TRα GS arteries (by 17.2 ± 1.1%NE, not significant vs WT). Inhibition of either eNOS or PI3K reduced T3-mediated vasodilation from 52.7 ± 4.5%NE to 28.5 ± 4.1%NE and 22.7 ± 2.9%NE, respectively. Removal of the endothelium abolished the T3-mediated vasodilation in rat mesenteric arteries (by 36.7 ± 5.4%NE vs 3.5 ± 6.2%NE). In vivo, T3 injection led to a rapid decrease of arterial BP in WT (by 13.9 ± 1.9 mm Hg) and TRα GS mice (by 12.4 ± 1.9 mm Hg), but not in TRα 0 mice (by 4.1 ± 1.9 mm Hg).

CONCLUSION

These results demonstrate that T3 acting through noncanonical TRα action affects cardiovascular physiology by inducing endothelium-dependent vasodilation within minutes via PI3K and eNOS activation.

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 the 24-h variability of blood pressure, ocular perfusion pressure, intraocular pressure, and visual field defect in thyroid associated orbitopathy

PURPOSE

To evaluate the relationship between the 24-h variability of blood pressure (BP), ocular perfusion pressure (OPP), intraocular pressure (IOP), and visual field (VF) defect in thyroid-associated orbitopathy (TAO).

METHODS

Thirty patients (60 eyes) with TAO were clinically examined in the Eye Hospital of Wenzhou Medical University. Patients were divided into two groups: one with VF defect (A) and the other without (B). Clinical parameters measured include 24-h IOP, 24-h blood pressure, orbital computed tomography (CT) scan, optical coherence tomography (OCT), and VFs. The pulse pressure (PP), mean arterial pressure (MAP), mean ocular perfusion pressure (MOPP), and 24-h fluctuations were calculated by formula.

RESULTS

The MOPP and MAP fluctuation were greater in group A than B (p < 0.05) and had significant negative correlation to mean deviation (MD) of VF (R = - 0.434 P = 0.001*). There was no statistical difference in the muscle index, medial rectus muscle thickness, and blood pressure between two groups. Although there were no significant differences in the mean IOP and IOP fluctuation between two groups, the incidence of IOP abnormalities has higher trend in group A. Patients with 24-h IOP fluctuation ≥8 mmHg and the mean IOP > 21 mmHg in the group A were more than group B.

CONCLUSIONS

Dysthyroid optic neuropathy (DON) might have multiple pathogenic mechanisms. In this study, 24-h MOPP fluctuation and medial rectus maximal diameter were all the risk factors for DON. Higher mean IOP and 24-h IOP fluctuation might be risk factors for DON.

The role of thyroid hormone in metabolism and metabolic syndrome

Metabolic syndrome (MetS) and thyroid dysfunction are common in clinical practice. The objectives of this review are to discuss some proposed mechanisms by which thyroid dysfunctions may lead to MetS, to describe the bidirectional relationship between thyroid hormones (THs) and adiposity and finally, to resume a list of recent studies in humans that evaluated possible associations between thyroid hormone status and MetS or its clinical components. Not solely THs, but also its metabolites regulate metabolic rate, influencing adiposity. The mechanisms enrolled are related to its direct effect on adenosine triphosphate (ATP) utilization, uncoupling synthesis of ATP, mitochondrial biogenesis, and its inotropic and chronotropic effects. THs also act controlling core body temperature, appetite, and sympathetic activity. In a bidirectional way, thyroid function is affected by adiposity. Leptin is one of the hallmarks, but the pro-inflammatory cytokines and also insulin resistance impact thyroid function and perhaps its structure. MetS development and weight gain have been positively associated with thyroid-stimulating hormone (TSH) in several studies. Adverse glucose metabolism may be related to hyperthyroidism, but also to reduction of thyroid function or higher serum TSH, as do abnormal serum triglyceride levels. Hypo- and hyperthyroidism have been related to higher blood pressure (BP), that may be consequence of genomic or nongenomic action of THs on the vasculature and in the heart. In summary, the interaction between THs and components of MetS is complex and not fully understood. More longitudinal studies controlling each of all confounding variables that interact with endpoints or exposure factors are still necessary.

In thyroxine-replaced hypothyroid postmenopausal women under simultaneous calcium supplementation, switch to oral liquid or softgel capsule L-thyroxine ensures lower serum TSH levels and favorable effects on blood pressure, total cholesterolemia and glycemia

PURPOSE

In postmenopausal women under L-T4 therapy, which was subsequently accompanied by calcium carbonate (CC) supplementation taken 6-8 h after tablet L-T4, TSH levels were greater than prior to adding CC. Total cholesterolemia [CHOL], fasting glycemia [FG], systolic and diastolic blood pressure [SBP, DBP] were also greater than baseline. Our aim was to explore the effects of either liquid or softgel capsule L-T4, while maintaining CC ingestion 6-8 h, later on TSH levels, CHOL, FG, SBP, and DBP.

METHODS

We proposed to 50 hypothyroid postmenopausal women under tablet L-T4 therapy, to switch to either liquid or softgel capsule L-T4 at the same daily dose while maintaining CC ingestion 6-8 h later. Sixteen women accepted [group I; liquid (n = 9), capsule (n = 7)], while 34 continued tablet L-T4 [group II, (n = 34)].

RESULTS

After 3 months, in group I, TSH decreased significantly (1.23 ± 0.49 vs. 1.80 ± 0.37 mU/L, P < 0.01), as did FG (80.7 ± 7.9 vs. 83.4 ± 6.3 mg/dL, P < 0.05); CHOL, SBP, and DBP decreased, though insignificantly. In contrast, in group II, TSH, FG, CHOL, SBP increased insignificantly, and DBP increased borderline significantly (69.7 ± 9 vs. 66.3 ± 6.5, P < 0.10). Compared to baseline (before adding CC), in group I, TSH was significantly lower (P < 0.01) and the other indices similar; in group II, TSH, FG, and SBP were significantly higher (P < 0.05), DBP borderline significantly higher (P < 0.10) and CHOL insignificantly higher. Performance of liquid L-T4 and capsule L-T4 was similar.

CONCLUSION

Delaying CC ingestion even by 6-8 h after taking tablet L-T4 is not entirely satisfactory, unlike liquid or softgel L-T4.

Thyroid and Cardiovascular Disease: Research Agenda for Enhancing Knowledge, Prevention, and Treatment

Thyroid hormones have long been known to have a range of effects on the cardiovascular system. However, significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing these effects and the optimal strategies for management of abnormalities in thyroid function in patients with and without preexisting cardiovascular disease. In September 2017, the National Heart, Lung, and Blood Institute convened a Working Group with the goal of developing priorities for future scientific research relating thyroid dysfunction to the progression of cardiovascular disease. The Working Group reviewed and discussed the roles of normal thyroid physiology, the consequences of thyroid dysfunction, and the effects of therapy in 3 cardiovascular areas: cardiac electrophysiology and arrhythmias, the vasculature and atherosclerosis, and the myocardium and heart failure. This report describes the current state of the field, outlines barriers and challenges to progress, and proposes research opportunities to advance the field, including strategies for leveraging novel approaches using omics and big data. The Working Group recommended research in 3 broad areas: (1) investigation into the fundamental biology relating thyroid dysfunction to the development of cardiovascular disease and into the identification of novel biomarkers of thyroid hormone action in cardiovascular tissues; (2) studies that define subgroups of patients with thyroid dysfunction amenable to specific preventive strategies and interventional therapies related to cardiovascular disease; and (3) clinical trials focused on improvement in cardiovascular performance and cardiovascular outcomes through treatment with thyroid hormone or thyromimetic drugs.

Thyroid and Cardiovascular Disease: Research Agenda for Enhancing Knowledge, Prevention, and Treatment

Thyroid hormones have long been known to have a range of effects on the cardiovascular system. However, significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing these effects and the optimal strategies for management of abnormalities in thyroid function in patients with and without preexisting cardiovascular disease. In September 2017, The National Heart, Lung, and Blood Institute convened a Working Group with the goal of developing priorities for future scientific research relating thyroid dysfunction to the progression of cardiovascular disease. The Working Group reviewed and discussed the roles of normal thyroid physiology, the consequences of thyroid dysfunction, and the effects of therapy in three cardiovascular areas: cardiac electrophysiology and arrhythmias, the vasculature and atherosclerosis, and the myocardium and heart failure. This report describes the current state of the field, outlines barriers and challenges to progress, and proposes research opportunities to advance the field, including strategies for leveraging novel approaches using omics and big data. The Working Group recommended research in three broad areas: 1) investigation into the fundamental biology relating thyroid dysfunction to the development of cardiovascular disease and into the identification of novel biomarkers of thyroid hormone action in cardiovascular tissues; 2) studies that define subgroups of patients with thyroid dysfunction amenable to specific preventive strategies and interventional therapies related to cardiovascular disease; and 3) clinical trials focused on improvement in cardiovascular performance and cardiovascular outcomes through treatment with thyroid hormone or thyromimetic drugs.

Role of Adipokines in the Association between Thyroid Hormone and Components of the Metabolic Syndrome

Metabolic syndrome (MS) increases cardiovascular risk. The role of thyroid hormone on components of MS is unclear. We analyzed a sample of 4733 euthyroid subjects from SardiNIA study. In female thyrotropin (TSH) was significantly and positively associated with triglycerides (Standardized regression coefficients (β) = 0.081, p < 0.001). Free thyroxine (FT4) was positively associated with HDL (β = 0.056, p < 0.01), systolic blood pressure (SBP) (β = 0.059, p < 0.001), diastolic blood pressure (DBP) (β = 0.044, p < 0.01), and fasting glucose (β = 0.046, p < 0.01). Conversely, FT4 showed a negative association with waist circumference (β = −0.052, p < 0.001). In TSH was positively associated with triglycerides (β = 0.111, p < 0.001) and FT4 showed a positive association with DBP (β = 0.51, p < 0.01). The addition of leptin and adiponectin to the regression models did not substantially change the impact of thyroid hormones on components of MS. Our data suggest that, even within the euthyroid range, excess of truncal adipose tissue is associated with variations in FT4. Leptin and adiponectin exert an additive effect rather than a causal effect. Additional studies should be performed to determine the clinical significance of this finding.

L-thyroxine malabsorption due to calcium carbonate impairs blood pressure, total cholesterolemia, and fasting glycemia

PURPOSE

Calcium carbonate was previously shown to interfere with L-thyroxine absorption. To estimate the magnitude of tablet L-thyroxine malabsorption caused by calcium carbonate, with resulting increase in serum thyrotropin (TSH), we performed a cohort study in a referral care center.

METHODS

Fifty postmenopausal hypothyroid L-thyroxine-treated women (age 71.7 ± 5.1 years) who added calcium supplementation (600-1000 mg/day) were considered. They were taking L-thyroxine 45-60 min before breakfast (setting 1). After 4.4 ± 2.0 years from initiation of L-thyroxine therapy, they took calcium supplemaentation within 2 h after L-thyroxine taking (setting 2) for 2.3 ± 1.1 years. Hence, we recommended postponing calcium intake 6-8 h after L-thyroxine (setting 3). We evaluated TSH levels, the prevalence of women with elevated TSH (>4.12 mU/L), total cholesterolemia, fasting glycemia, blood pressure, and the prevalence of hypercholesterolemia, hyperglycemia, and hypertension.

RESULTS

TSH levels were 3.33 ± 1.93 mU/L versus 1.93 ± 0.51 or 2.16 ± 0.54 comparing setting 2 with setting 1 or 3 (P < 0.001, both). In setting 2, 18% women had elevated TSH versus none in setting 1 or 3 (P < 0.01). Total cholesterolemia, fasting glycemia, systolic, and diastolic blood pressure were also significantly higher in setting 2 compared to settings 1 and 3. For every 1.0 mU/L increase within the TSH range of 0.85-6.9 mU/L, total cholesterolemia, glycemia, systolic, and diastolic blood pressure increased by 12.1, 3.12 mg/dL, 2.31, and 2.0 mmHg, respectively.

CONCLUSIONS

Monitoring of hypothyroid patients who ingest medications that decrease L-thyroxine absorption should not be restricted to solely measuring serum TSH.

Hypertension in Thyroid Disorders

Arterial hypertension represents a major global health concern; more than one fourth of the population is affected by high blood pressure. Albeit the underlying cause of the disease remains unclear in the vast majority of the cases, ~10% are of secondary origin. Endocrine disorders are common illnesses and some of them may lead to elevated blood pressure, among which thyroid diseases are of high prevalence and often overlooked, especially in mild cases. Overt and subclinical hyper- and hypothyroidism can both lead to (mostly mild) hypertension; however, the underlying mechanisms are only partially understood. The results of clinical studies are often controversial. During the past decades, some genetic mutations in the hypothalamus-pituitary-thyroid axis with cardiovascular consequences were revealed. Atherosclerotic changes resulting from lipid abnormalities due to thyroid dysfunction also affect the vasculature and can cause elevated blood pressure. The review gives a synopsis of our knowledge how thyroid hormone metabolism and functional thyroid diseases affect the cardiovascular system, their negative impact and causative role in the development of hypertension.

The relationship between hyperthyrotropinemia and metabolic and cardiovascular risk factors in a large group of overweight and obese children and adolescents

PURPOSE

Mild TSH elevations are frequently observed in obese patients, in the absence of any detectable thyroid disease. Our objective is to evaluate the relationship between the raised TSH levels and the biochemical and clinical consequences of obesity.

METHODS

This is a retrospective cross-sectional study of a large population of obese children and adolescents. We evaluated 833 subjects (340 m, 493 f), aged 14.4 ± 2.5 (range 5.2-18.5) years, height SDS 0.27 ± 1.04 (-3.49-4.35), and BMI SDS 2.94 ± 0.59 (1.60-4.68). Body composition, free T4, TSH, anti-TPO antibodies, anti-TG antibodies, inflammation markers (total WBC and the subtypes, ultrasensitive C-reactive protein), and metabolic parameters [AST, ALT, γGT, ALP, glycaemia, insulin, total cholesterol (TC), HDL-cholesterol (HDL-C), and LDL-cholesterol (LDL-C), triglycerides (TG)] were measured, and oral disposition index (ODI) and cardiovascular risk factors (TC/HDL-C and TG/HDL-C) were calculated. After exclusion of the subjects showing anti-thyroid antibodies, the remaining 779 (325 m, 454 f) were then subdivided into two subgroups according to a TSH value below (group A) or above (group B) 4.5 mU/L.

RESULTS

Clinical characteristics and hematological markers of patients with and without positive anti-thyroid antibodies were similar, with the exception of higher TSH levels in the latter group. Using analysis of covariance, the subjects of group B had significantly higher values of TC (170.3 ± 28.7 vs 163.3 ± 32.9 mg/dL; p < 0.05), systolic (125.8 ± 13.5 vs 124.5 ± 13.1 mm/Hg), and diastolic blood pressure (79.2 ± 8.0 vs 77.9 ± 8.2 mm/Hg) than subjects of group A. No difference was observed in body composition, ODI, and the cardiovascular risk factors between these two groups.

CONCLUSION

TSH elevation in overweight and obese children and adolescents, being associated with a higher TC and blood pressure, might negatively influence the cardiac status. Longitudinal studies are requested, however, to confirm this hypothesis and, therefore, to conclude whether a substitutive treatment with l-thyroxine is really needed in these patients.

Repetitive Transcranial Magnetic Stimulation (rTMS) Modulates Lipid Metabolism in Aging Adults

Hyperlipidemia, one of the cardiovascular (CV) risk factors, is associated with an increase in the risk for dementia. Repetitive transcranial magnetic stimulation (rTMS) was applied over the right dorsolateral prefrontal cortex (DLPFC) to modulate serum lipid levels in older adults. Participants received 10 sessions of rTMS or sham stimulation intervention within 2 weeks. The serum lipid and thyroid hormone-related endocrine levels were assessed before and after the treatment. We found that rTMS significantly decreased serum lipid levels, including the total cholesterol (CHO) and triglyceride (TG); meanwhile, it also increased the thyroid-stimulating hormone (TSH) as well as thyroxine (T4) levels. This suggests that rTMS modulated the serum lipid metabolism by altering activity in the hypothalamo-pituitary-thyroid (HPT) axis. The trial was registered on the website of Chinese Clinical Trial Registry (http://www.chictr.org.cn).

Thyroid Function, Cardiovascular Risk Factors, and Incident Atherosclerotic Cardiovascular Disease: The Atherosclerosis Risk in Communities (ARIC) Study

CONTEXT

Cardiovascular outcomes in mild thyroid dysfunction (treatment controversial) and moderate or severe dysfunction (treatment standard) remain uncertain.

OBJECTIVE

To examine cross-sectional and prospective associations of thyroid function with cardiovascular risk factors and events.

DESIGN

In the Atherosclerosis Risk in Communities Study, we measured concentrations of thyrotropin, free thyroxine, and total triiodothyronine (T3) in stored serum samples originally collected in 1990-1992. We used multivariable linear regression to assess cross-sectional associations of thyroid function with cardiovascular risk factors and Cox regression to assess prospective associations with cardiovascular events. Follow-up occurred through 31 December 2014.

SETTING

General community.

PARTICIPANTS

Black and white men and women from the United States, without prior myocardial infarction (MI), stroke, or heart failure.

MAIN OUTCOMES AND MEASURES

Cross-sectional outcomes were blood pressure, glycemic markers, and blood lipids. Prospective outcomes were adjudicated fatal and nonfatal MI and stroke.

RESULTS

Among 11,359 participants (57 ± 6 years, 58% women), thyroid function was more strongly associated with blood lipids than blood pressure or glycemic measures. Mean adjusted differences in low-density lipoprotein cholesterol were +15.1 (95% confidence interval: 10.5 to 19.7) and +3.2 (0.0 to 6.4) mg/dL in those with moderate/severe and mild chemical hypothyroidism, relative to euthyroidism; an opposite pattern was seen in hyperthyroidism. Similar differences were seen in triglycerides and non-high-density lipoprotein cholesterol. With a 22.5-year median follow-up, 1102 MIs and 838 strokes occurred, with similar outcomes among baseline thyroid function groups and by T3 concentrations.

CONCLUSIONS

Hypothyroidism is associated with hyperlipidemia, but the magnitude is small in mild chemical hypothyroidism, and cardiovascular outcomes are similar between thyroid function groups.

Association of high normal HbA1c and TSH levels with the risk of CHD: a 10-year cohort study and SVM analysis

This study aimed to determine the association between the clinical reference range of serum glycated hemoglobin A1c (HbA1c) and thyrotropin (TSH) and the risk of coronary heart disease (CHD) in non-diabetic and euthyroid patients. We examined baseline HbA1c and TSH in 538 healthy participants, and then analyzed the associations and potential value of these indicators for predicting CHD using Cox proportional hazard and support vector machine analyses. During the median follow-up of 120 months, 39 participants later developed CHD. The baseline HbA1c and TSH within the reference range were positively associated with CHD risk. No correlation and interaction were found between the baseline HbA1c and TSH for the development of CHD. Disease event-free survival varied among participants with different baseline HbA1c quintiles, whereas disease event-free survival was similar for different TSH tertiles. The combination of these baselines showed sensitivity of 87.2%, specificity of 92.7%, and accuracy of 92.3% for identifying the participants who will later develop CHD. Relatively high but clinically normal HbA1c and TSH levels may increase the risk of CHD. Therefore, the combination of these indicators can serve as a biomarker for identifying healthy individuals from those who would later develop CHD.

Thyrotropin Levels Are Associated with Cardiometabolic Risk Factors in Euthyroid Adolescents

BACKGROUND

Increased thyrotropin (TSH) levels and free triiodothyronine to free thyroxine (fT3:fT4) ratios, even within the euthyroid range, have been associated with cardiometabolic risk factors in adults but are less characterized in youth. This study sought to determine relations between TSH, thyroid hormones, and cardiometabolic risk factors in euthyroid adolescents.

METHODS

Data were extracted from the United States National Health and Nutrition Examination Survey, 2007-2010, for univariate and multivariate analyses of TSH, thyroid hormones, body mass index (BMI), blood pressure, lipids, and glucose metabolism. Subjects aged 12-18 years, with normal TSH and antithyroid peroxidase antibody levels, and without a history of thyroid disease, diabetes, or treatment of hypertension/dyslipidemia (n = 1167) were included. TSH and thyroid hormones were assessed for impact on BMI Z-score, systolic blood pressure (SBP) diastolic blood pressure, total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, triglycerides, and glucose metabolism.

RESULTS

Univariate analyses revealed positive linear relations between TSH and SBP, TC, fasting and two-hour glucose, and homeostasis model assessment of insulin resistance (HOMA-IR). The fT3:fT4 ratio negatively correlated with high-density lipoprotein cholesterol but positively with BMI Z-score, SBP, triglycerides, fasting and two-hour glucose, fasting insulin, and HOMA-IR. In multivariate analyses controlling for age, sex, race/ethnicity, and BMI Z-score, relations between TSH and both TC and fasting glucose remained significant, and the fT3:fT4 ratio was positively associated with fasting glucose and HOMA-IR.

CONCLUSIONS

In an unselected population of euthyroid U.S. adolescents, TSH and thyroid hormones correlate with multiple cardiometabolic risk factors, with age- and sex-independent effects on cholesterol and glucose metabolism.

Change in serum TSH levels within the reference range was associated with variation of future blood pressure: a 5-year follow-up study

Controversy exists on the relationship between serum thyrotropin (TSH) and blood pressure, and only a few prospective studies are available up to now. The study aimed to investigate the association between serum TSH within the reference range and blood pressure through a 5-year follow-up study. A total of 623 subjects with normal TSH were followed up for 5 years, including the measurement of demographic data, blood pressure, height, weight and serum TSH. Finally, 531 subjects were included in this prospective study. Body mass index (BMI), prevalence of hypertension, and systolic and diastolic blood pressure were all higher at follow-up than at baseline. Adjusted for age, gender, smoking status, BMI and homoeostasis model assessment of insulin resistance (HOMA-IR) at baseline, multiple linear regression analyses found no relationship between serum TSH at baseline and levels of blood pressure at follow-up, but the changes in serum TSH levels during follow-up was positively associated with the changes in systolic blood pressure (B=2.134, P<0.05), which became more significant in women but not significant in men. The change of systolic blood pressure in group of TSH increase >0.5 mIU l^-1 was significantly higher than in group of TSH decrease >0.5 mIU l^-1 within reference, after adjusting for age, gender, smoking status, BMI and HOMA-IR at baseline. This result became more significant in women, but no statistical significance was observed in men. Co-variation with serum TSH levels and blood pressure was observed during 5-year follow-up among people with normal TSH.

Association between thyroid-stimulating hormone and blood pressure in adults: an 11-year longitudinal study

BACKGROUND

The results of longitudinal studies on the association between thyroid function and blood pressure (BP) are divided. This study aimed to investigate this association in cross-sectional and longitudinal settings in a nationwide, random sample representative of the Finnish adult population aged 30 and over.

METHODS

The study sample was randomly drawn from the population register. A total of 5655 participants were included in the baseline analyses and 3453 in the 11-year prospective analyses. The associations between baseline TSH and (i) BP and BP change over time; and (ii) prevalent and incident hypertension were assessed using linear and logistic models, adjusted for age, gender, smoking and body mass index.

RESULTS

A positive association (β ± standard error) was observed between TSH and diastolic (0·36 ± 0·12, P = 0·003) but not systolic BP (0·16 ± 0·21, P = 0·45) at baseline. TSH was negatively associated with 11-year BP change in men (systolic: -0·92 ± 0·41, P = 0·03; diastolic: -0·66 ± 0·26, P = 0·01) but not in women (P ≥ 0·09 for systolic and diastolic BP change). Participants in the highest TSH tertile within the TSH reference interval (0·4-3·4 mU/L), as compared with the lowest, had increased odds of prevalent (odds ratio 1·22, 95% confidence interval 1·05-1·43, P = 0·01) but not incident hypertension (odds ratio 0·93, 95% confidence interval 0·73-1·19, P = 0·58).

CONCLUSIONS

A modest association was found between increasing TSH and prevalent but not incident hypertension. TSH was inversely associated with BP change in men in our study. These findings contest an independent role of thyroid function at normal to near-normal levels in the pathogenesis of hypertension.

A high normal thyroid-stimulating hormone is associated with arterial stiffness, central systolic blood pressure, and 24-hour systolic blood pressure in males with treatment-naïve hypertension and euthyroid

BACKGROUND

We compared the results of laboratory examinations, echocardiography, arterial stiffness, central blood pressure (BP) and ambulatory BP monitoring (ABPM) between treatment-naïve patients with low normal thyroid-stimulating hormone (TSH) and those with high normal TSH levels.

METHODS

A total of 285 consecutively-eligible patients with both treatment-naïve hypertension and euthyroid were divided into two groups: those with low-normal TSH (0.40-1.99 μIU/mL, group 1) and high-normal TSH (2.00-4.50 μIU/mL, group 2) and compared according to group and gender.

RESULTS

Males were divided into group 1 (n = 113, 68.9%) and group 2 (n = 51, 31.1%) and females were divided into group 1 (n = 71, 58.7%) and group 2 (n = 50, 41.3%). Multivariate analyses revealed that the augmentation index (71.0 [adjusted mean] ± 1.7 [standard error] vs. 78.8 ± 2.5%, P = 0.045), central systolic BP (SBP) (143.3 ± 2.1 vs. 153.0 ± 3.2 mmHg, P = 0.013), systemic vascular resistance (SVR, 21.4 ± 0.6 vs. 23.9 ± 0.9 mmHg/L/min, P = 0.027), SBP during daytime (144.1 ± 1.4 vs. 151.6 ± 2.1 mmHg, P=0.004) and nighttime (130.4 ± 1.6 vs. 138.5 ± 2.5 mmHg, P=0.008), and nighttime pulse pressure (PP, 47.2 ± 0.9 vs. 51.7 ± 1.4 mmHg, P = 0.010) were significantly higher while cardiac output (5.4 ± 0.1 vs. 4.8 ± 0.2L/min, P = 0.043) and PP amplification (1.02 ± 0.02 vs. 0.94 ± 0.03, P = 0.039) were significantly lower in the male group 2 than in the male group 1. However, there were no significant differences between the two groups in females.

CONCLUSIONS

Treatment-naïve hypertensive males with high normal TSH and euthyroid showed higher arterial stiffness, central SBP, SVR, and SBP in ABPM and lower cardiac output and PP amplification as compared to the the low normal TSH group, but not females.

High serum thyrotropin levels are associated with retinal arteriolar narrowing in the general population

BACKGROUND

Recent studies have shown associations of hypothyroidism with arterial blood pressure, atherosclerosis, and inflammation. Based on these pathways, there might also be an association between hypothyroidism and retinal arteriolar narrowing (RAN), a marker of microvascular damage from hypertension, atherosclerosis, and inflammation. Against this background, the aim of this study was to investigate the putative association between serum thyrotropin (TSH) levels and RAN defined by arterio-venous ratio (AVR) from static vessel analysis.

METHODS

We used data from 3189 individuals from the second population-based cohort of the Study of Health in Pomerania (SHIP-TREND-0). Thyroid function was defined according to serum TSH and serum diiodothyronine (3,5-T2) levels. Low and high serum TSH levels were defined by the cutoffs 0.3 mIU/L and 3.0 mIU/L. Fundus photography of the central retina was recorded with a nonmydriatic camera, and images were evaluated by one experienced reader. An AVR <0.8 was defined as decreased. Serum TSH levels, low and high TSH, and serum 3,5-T2 levels were associated with AVR by linear regression and with AVR <0.8 by Poisson regression, both adjusted for age, sex, cigarette smoking, alcohol consumption, and intake of beta-blockers.

RESULTS

Serum TSH levels were significantly associated with AVR (β=-0.028 [CI -0.049 to -0.007]; p=0.009) and with a decreased AVR <0.8 (relative risk=2.05 [CI 1.13-3.73]; p=0.019). Individuals with high TSH had a 1.43 higher risk for a decreased AVR ([CI 1.04-1.96]; p=0.027) than individuals with serum TSH levels within the reference range. Serum 3,5-T2 levels were also associated with a decreased AVR (relative risk for an increase of 1 nM=0.45 [CI 0.23-0.87]; p=0.017).

CONCLUSIONS

Our results substantiate evidence for an association between hypothyroidism and RAN. Potential mechanisms explaining this association are long-term hypertension, atherosclerotic processes, and inflammation.

Autoimmune thyroiditis as a risk factor for stroke: a historical cohort study

OBJECTIVE

To investigate the effect of autoimmune thyroiditis (AIT) on risk of stroke and to assess whether any increased risk (1) varied by AIT duration, and (2) was independent of classic cardiovascular risk factors.

METHODS

This was a large historical cohort study using data from The Health Improvement Network Database. Rates of first stroke during follow-up in thyroxine-treated patients with AIT (n = 34,907) were compared with those in matched individuals without AIT (n = 149,632) using random-effects Poisson regression models.

RESULTS

There was strong evidence for a slightly increased risk of stroke in patients with AIT (adjusted rate ratio = 1.10, 95% confidence interval: 1.01-1.20). The observed increase was partly independent of cardiovascular risk factors. Higher effect sizes were identified in the first year after AIT diagnosis (rate ratio = 1.33, 95% confidence interval: 1.14-1.56) but not in the long-term, consistent with a residual effect of hypothyroidism.

CONCLUSION

Our results support the hypothesis of a slightly increased risk of stroke in patients with AIT. The higher effect size found soon after AIT diagnosis suggests an increased cardiovascular risk due to thyroid-hormone deficiency rather than a cumulative effect of autoimmune pathology. Better screening and early treatment of patients with asymptomatic hypothyroid AIT could help reduce excess risk of stroke in the first year after diagnosis.

Triiodothyronine and free thyroxine levels are differentially associated with metabolic profile and adiposity-related cardiovascular risk markers in euthyroid middle-aged subjects

BACKGROUND

We have previously shown that in healthy young men, a less favorable body composition is associated with higher free triiodothyronine (fT3) levels within the euthyroid range. Besides, a higher free-triiodothyronine-to-free-thyroxin (fT3-to-fT4) ratio has been related to a less favorable metabolic phenotype and more placental growth in pregnant women. In the present study, we therefore investigated whether serum thyrotropin (TSH), thyroid hormone levels, and the fT3-to-fT4 ratio are associated with metabolic and adiposity-related cardiovascular risk markers in a healthy population of middle-aged euthyroid men and women.

METHODS

Thyroid parameters were measured in 2524 generally healthy subjects from the Asklepios Study (35-55 years, mean age 46 years). Analyses were restricted to 2315 subjects (1138 women and 1177 men), not using thyroid medication, not having anti-TPO levels above clinical cutoff values or TSH levels outside the reference range (0.27-4.2 mU/L). Twenty-seven percent of the women and 47.5% of the men were overweight, while 13% of women and 17% of men were obese. Twenty percent of the subjects were active smokers. Serum thyroid function parameters were determined by electrochemiluminescence.

RESULTS

fT3 and the fT3-to-fT4 ratio were positively related to body mass index (BMI), waist circumference, and components of metabolic syndrome, that is, triglycerides, systolic and diastolic blood pressure, and fasting plasma glucose, and negatively with HDL-cholesterol levels, whereas fT4 was negatively associated with BMI, waist circumference, and triglycerides (p<0.001). TSH related positively with total cholesterol levels (p<0.01), triglycerides, and systolic and diastolic blood pressure (p<0.001). The fT3-to-fT4 ratio was further positively associated with the adiposity-related inflammation markers interleukin-6 and high-sensitivity C-reactive protein and to pulse wave velocity. All associations were adjusted for sex, age, height, and smoking, and most associations persisted after additional adjustment for weight or waist circumference.

CONCLUSION

In healthy euthyroid middle-aged men and women, higher fT3 levels, lower fT4 levels, and thus a higher fT3-to-fT4 ratio are consistently associated with various markers of unfavorable metabolic profile and cardiovascular risk.

Effects of recombinant human thyrotropin administration on 24-hour arterial pressure in female undergoing evaluation for differentiated thyroid cancer

Objective. Thyroid-stimulating-hormone (TSH) receptors are expressed in endothelial cells. We investigated whether elevated TSH levels after acute recombinant TSH (rhTSH) administration may result in alterations in blood pressure (BP) in premenopausal women with well-differentiated thyroid carcinoma (DTC). Designs. Thirty euthyroid DTC female patients were evaluated by rhTSH stimulation test (mean age 40.4 ± 8.6 years). A 24 h ambulatory systolic and diastolic blood pressure (SBP, DBP) monitoring (24 hr ABPM) was performed on days 2-3(D2-3). TSH was measured on day 1(D1), day 3(D3), and day 5(D5). Central blood pressure was evaluated on D3. Twenty-three patients were studied 1-4 weeks earlier (basal measurements). Results. TSH levels were D1: median 0.2 mU/L, D3: median 115.0 mU/L, and D5: median 14.6 mU/L. There were no significant associations between TSH on D1 and D3 and any BP measurements. Median D5 office-SBP and 24 h SBP, DBP, and central SBP were correlated with D5-TSH (P < 0.04). In those where a basal 24 h ABPM had been performed median pulse pressure was higher after rhTSH-test (P = 0.02). Conclusions. TSH, when acutely elevated, may slightly increase SBP, DBP, and central SBP. This agrees with previous reports showing positive associations of BP with TSH.