Thyroid disease and lipids

The thyroid receptor modulator KB3495 reduces atherosclerosis independently of total cholesterol in the circulation in ApoE deficient mice

BACKGROUND

Thyroid hormones (TH) regulate cholesterol metabolism but their use as lipid-lowering drugs is restricted due to negative cardiac effects. TH mimetic compounds modulating TH receptor β (THRβ) have been designed as potential drugs, reducing serum cholesterol levels while avoiding apparent deleterious cardiac effects.

OBJECTIVE

Using ApoE deficient mice, we examined whether KB3495, a TH mimetic compound, reduces atherosclerosis and if there is a synergistic effect with atorvastatin. The effect of KB3495 was investigated after 10 and 25 weeks.

RESULTS

KB3495 treatment reduced atherosclerotic plaque formation in aorta and decreased the cholesteryl ester (CE) content by 57%. Treatment with KB3495 was also associated with a reduction of macrophage content in the atherosclerotic plaques and reduced serum levels of IL-1β, TNFalpha, IL-6, Interferon γ, MCP-1 and M-CSF. Serum lipoprotein analysis showed no change in total cholesterol levels in ApoB-containing lipoproteins. KB3495 alone increased fecal BA excretion by 90%. The excretion of neutral sterols increased in all groups, with the largest increase in the combination group (350%). After 25 weeks, the animals treated with KB3495 showed 50% lower CE levels in the skin and even further reductions were observed in the combination group where the CE levels were reduced by almost 95% as compared to controls.

CONCLUSION

KB3495 treatment reduced atherosclerosis independently of total cholesterol levels in ApoB-containing lipoproteins likely by stimulation of sterol excretion from the body and by inhibition of the inflammatory response.

A cross-sectional study of the association between circulating TSH level and lipid profile in a large Spanish population

OBJECTIVE

Some evidence suggests that high serum TSH levels are associated with an adverse lipid profile, but this association is not clear when plasma TSH is within the reference range. Nevertheless, these studies have never been conducted in Spain, a country with a strong adherence to the Mediterranean diet. The study aim was to analyse the association between blood TSH levels and circulating lipids in a large Spanish population and set up a TSH reference range in different age, gender and Body Mass Index (BMI) subpopulations from our cohort.

DESIGN

Cross-sectional study on 20 783 subjects.

PATIENTS

We analysed circulating levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDLc), high-density lipoprotein cholesterol (HDLc) and triglycerides (TG) and compared them with TSH serum levels. Discriminant function analysis was used to determine the TSH cut-off level from where hyperlipidaemia developed.

RESULTS

In individuals free of thyroid dysfunction, the mean and the 95% TSH (mU/l) reference limits were 2·20 and 0·72-4·43, respectively. We observed a sex-related difference in TSH concentration (men, 2·07 and 0·72-4·29; women, 2·29 and 0·72-4·49; P < 0·01). We also observed a weight-related difference in TSH concentration (BMI < 30 kg/m(2) , 2·16 and 0·72-4·39; BMI ≥ 30 kg/m(2) , 2·28 and 0·71-4·47; P < 0·01). TSH was positively associated with TC, TG and LDLc levels and negatively with HDLc.

CONCLUSION

We found an association between TSH and lipids in that as TSH increased, the lipid profile became less favourable, even within the normal range. Additionally, TSH reference ranges varied according to gender, age and BMI.

Chromosome 19 open reading frame 80 is upregulated by thyroid hormone and modulates autophagy and lipid metabolism

The thyroid hormone, T 3, regulates cell growth, differentiation and development through binding to the nuclear thyroid hormone receptor (THR), a member of the steroid/TR superfamily of ligand-dependent transcriptional factors. T 3 modulates lipid metabolism in liver, although the detailed molecular mechanisms are unclear at present. Here, by a microarray analysis, we identified a novel chromosome 19 open reading frame 80 (C19orf80) which was activated by T 3. T 3 stimulation led to upregulation of both mRNA and protein levels of C19orf80. Immunofluorescence analysis revealed a vesicle-like pattern of C19orf80 around lipid droplets or within the lysosome-associated compartment in cells. Furthermore, T 3 treatment as well as C19orf80 overexpression specifically activated the autophagic response and lipid metabolism, as observed from lipidated LC3 (LC3-II) and levels of oxygen consumption rate, respectively. Reciprocally, knockdown of C19orf80 obstructed T 3-activated autophagy and lipolysis. Moreover, treatment with autolysosome maturation inhibitors, ammonium chloride and chloroquine, not only suppressed the T 3-activated autophagic process but also lipid metabolism. Our results collectively suggested that T 3 regulates lipid metabolism through a C19orf80-activated autophagic process.

Pathology, pathophysiology, and treatment strategies of endocrine disorders and their cardiac complications

The cardiovascular system is affected by a multitude of endocrine disorders, including dysfunction of the thyroid, calcium, glucocorticoids, insulin/glucose, and growth hormone axes. Since most of these changes in the cardiovascular system are reversible when treated, early diagnosis is important, as if left untreated, they may become fatal. This review focuses on the pathophysiology, clinical presentation, pathology, and treatment of patients with these endocrine diseases who present with a variety of cardiovascular manifestations. Neuroendocrine tumors presenting with the carcinoid syndrome and their cardiovascular manifestations are also discussed.

Evaluation of epicardial fat tissue thickness in patients with Hashimoto thyroiditis

OBJECTIVE

Hypothyroidism, whether overt or subclinical, has multiple effects on the cardiovascular system. Epicardial fat tissue (EFT) is closely related to cardiovascular disorders and atherosclerosis. Our study aimed to assess EFT thickness and carotid artery intima-media thickness (CIMT) in patients with Hashimoto's thyroiditis (HT) displaying overt and subclinical hypothyroidism (SCH).

DESIGN AND PATIENTS

The study included 33 patients with SCH and 24 patients with overt hypothyroidism (OH) with HT as well as 32 healthy controls. EFT thickness, CIMT, thyroid hormone levels and lipid parameters were measured in all subjects. Correlation analysis and linear regression analysis were performed for EFT thickness.

RESULTS

Mean EFT thickness was 2·89 ± 0·38, 3·53 ± 0·92 and 4·56 ± 1·61 mm in control, SCH and OH groups, respectively (P < 0·001). EFT thickness of OH patients was high compared with SCH and control subjects (P < 0·01 and <0·001, respectively). CIMT of OH patients was high compared with SCH and control subjects (P < 0·01 and <0·001, respectively). In addition, EFT was significantly thicker in SCH patients than in controls (P < 0·05). Correlation analysis showed that EFT thickness was significantly positively correlated with CIMT, age, body mass index, systolic blood pressure, thyroid-stimulating hormone, total and LDL cholesterol and triglyceride and negatively correlated with free T4. In the regression analysis, EFT thickness retained its independent and positive association with CIMT, patient group (particularly OH) and systolic blood pressure.

CONCLUSIONS

Epicardial fat tissue thickness may be a useful indicator of early atherosclerosis in SCH and OH patients with HT.

Inappropriate heat dissipation ignites brown fat thermogenesis in mice with a mutant thyroid hormone receptor α1

Thyroid hormone is a major regulator of thermogenesis, acting both in peripheral organs and on central autonomic pathways. Mice heterozygous for a point mutation in thyroid hormone receptor α1 display increased thermogenesis as a consequence of high sympathetic brown fat stimulation. Surprisingly, despite the hypermetabolism, their body temperature is not elevated. Here we show, using isolated tail arteries, that defective thyroid hormone receptor α1 signaling impairs acetylcholine-mediated vascular relaxation as well as phenylephrine-induced vasoconstriction. Using infrared thermography on conscious animals, we demonstrate that these defects severely interfere with appropriate peripheral heat conservation and dissipation, which in turn leads to compensatory alterations in brown fat activity. Consequently, when the vasoconstrictive defect in mice heterozygous for a point mutation in thyroid hormone receptor α1 was reversed with the selective α1-adrenergic agonist midodrine, the inappropriate heat loss over their tail surface was reduced, normalizing brown fat activity and energy expenditure. Our analyses demonstrate that thyroid hormone plays a key role in vascular heat conservation and dissipation processes, adding a unique aspect to its well-documented functions in thermoregulation. The data thus facilitate understanding of temperature hypersensitivity in patients with thyroid disorders. Moreover, the previously unrecognized connection between cardiovascular regulation and metabolic activity revealed in this study challenges the interpretation of several experimental paradigms and questions some of the currently derived hypotheses on the role of thyroid hormone in thermogenesis.

Thyroid hormone status and health-related quality of life in the LifeLines Cohort Study

BACKGROUND

Thyroid disorders are prevalent in Western society, yet many subjects experience limited symptoms at diagnosis, especially in hypothyroidism. We hypothesize that health-related quality of life (HR-QOL) is more severely impaired in subjects with more abnormal thyroid hormone function tests.

METHODS

This is a cross-sectional study of Dutch adults participating in the LifeLines Cohort Study between December 2009 and August 2010. In 9491 Western European participants (median age 45 years; 3993 men and 5498 women), without current or former use of thyroid medication, we compared HR-QOL using the RAND 36-Item Health Survey between subjects with normal thyrotropin (TSH) values and subjects with disturbed thyroid hormone status (serum TSH, free thyroxine, and free triiodothyronine). The influence of possible confounders (age, smoking, co-morbidity) on HR-QOL was evaluated as well.

RESULTS

Suppressed TSH values (TSH < 0.5 mU/L) were found in 114 (1.2%), while 8334 (88.8%) had TSH within the normal range, 973 participants (10.3%) had TSH between 4 and 10 mU/L, and 70 (0.7%) had TSH > 10 mU/L. Men had a higher HR-QOL than women (70-92 vs. 65-89; p < 0.001), except for the domain "general health" (72 vs. 72; p = 0.692). Men with suppressed or elevated TSH values did not score significantly lower than euthyroid men for any of nine domains of the RAND 36-Item Health Survey. Compared with euthyroid women, women with suppressed TSH scored significantly lower in the domains "physical functioning" (84 vs. 89, p = 0.013) and "general health" (67 vs. 72, p = 0.036). Women with markedly elevated TSH (> 10 mU/L) had a score in all HR-QOL domains that was similar to that of women with normal TSH values. There were no differences in the physical component score and the mental component score between any of the TSH groups. Physical component score and mental component score were mainly determined by smoking status, co-morbidity, and body mass index or waist circumference.

CONCLUSIONS

In this population-based study, HR-QOL scores of subjects with suppressed TSH values or markedly elevated TSH values were generally not significantly lower than those of subjects with normal or mildly elevated TSH values.

Subclinical hypothyroidism and the metabolic syndrome: A meta-analysis of cross-sectional studies

AIM: To determine the relationship between subclinical hypothyroidism (SCH) and the metabolic syndrome (MS).

METHODS: We performed a systematic search of databases [MEDLINE (July 1950 to July 2012), EMBASE (July 1966 to July 2012)] and the references of identified studies. Completely published cross-sectional studies of a general population involving SCH and the MS were included. The pooled odds ratio and weighted mean difference (WMD) for the outcomes were calculated using random-effects models.

RESULTS: Six cross-sectional studies with 19546 participants were included. In total, 398 of 1324 participants (30.06%) in the SCH group had the MS compared with 4975 of 18222 participants (27.30%) in the euthyroid group [OR = 1.20; 95%CI: 1.05-1.36; P = 0.004; χ² = 2.53 (P = 0.773); I² = 0%]. Further analysis of the components of the MS showed that SCH was associated with increased body mass index (WMD, 0.32 kg/m²; 95%CI: 0.04-0.61; P = 0.026), systolic blood pressure (WMD, 2.62 mmHg; 95%CI: 1.35-3.89; P < 0.001) and triglyceride (WMD, 0.25 mmol/L; 95%CI: 0.23-0.28; P < 0.001).

CONCLUSION: Based on the cross-sectional data, SCH may be associated with an increased risk of the MS, which could be attributed to the increased risk of metabolic components.

Metabolic profiles in adults with autism spectrum disorder and intellectual disabilities

INTRODUCTION

Low levels of blood cholesterol have been found in some children with autism spectrum disorders (ASD). Psychotropic medications, commonly used by people with ASD and people with intellectual disabilities (ID) are frequently associated with altered metabolic profiles.

PURPOSE

We aimed to compare metabolic features of adults with ASD or ID with those of a community-based population.

SUBJECTS AND METHODS

Data on blood fasting glucose (FBG), lipid profile, liver enzyme profile, TSH, BMI, medications and diagnoses of 80 adults with ASD, 77 adults with ID and 828 control adults were drawn from medical charts/database. Candidates that used glucose or lipid lowering medications were not included.

RESULTS

Total-cholesterol levels of people with ASD and ID were significantly lower than those of the controls (168.3 ± 32.78, 168.2 ± 32.91, 185.4 ± 40.49 mg/dL, respectively, P<0.001) but after adjusting for gender, age and BMI and using Bonferroni correction, the significance was lost. Compared to controls, ASD and ID had significantly lower FBG (by -14.45 ± 1.81, -14.58 ± 1.54 mg/dl, respectively; P<0.001 for both) and liver enzymes, despite using psychotropic medications.

DISCUSSION AND CONCLUSION

In contrast to other psychiatric patients receiving similar medications, people with ASD and ID have unaltered lipid profiles and lower glucose and liver enzyme levels compared to a community-based population.

Unchanged serum adipokine concentrations in the setting of short-term thyroidectomy-induced hypothyroidism

OBJECTIVE

To investigate short-term effects of thyroidectomy-induced hypothyroidism on leptin, adiponectin, and resistin concentrations in association with anthropometric data.

METHODS

Thirty premenopausal women with euthyroid nodular goiter-mean age, 44.0 ± 11.6 years; mean body mass index (BMI), 28.6 ± 5.9 kg/m2; 13 obese, 7 overweight, and 10 normal weight subjects-scheduled for total thyroidectomy were included in the study. Serum leptin, adiponectin, resistin, free triiodothyronine, free thyroxine, thyroid-stimulating hormone, glucose, insulin, and C-reactive protein concentrations, lipid profile, and anthropometric variables were determined in the euthyroid state (preoperatively) and the hypothyroid state (postoperatively, with a thyroid-stimulating hormone concentration >30 mIU/L).

RESULTS

Body weight, BMI, waist and hip circumferences, body fat mass, and serum lipid concentrations increased significantly after thyroidectomy. No significant difference was found between preoperative and postoperative serum leptin, adiponectin, and resistin concentrations. Fat tissue mass-corrected leptin, adiponectin, and resistin concentrations did not differ significantly between euthyroid and hypothyroid periods. Thyroid hormone concentrations showed no significant correlations with adipokine levels.

CONCLUSION

Serum adipokine concentrations seem not to change significantly during short-term thyroidectomy-induced hypothyroidism despite significant increases in body weight, BMI, fat mass, and lipid concentrations.

Subclinical hypothyroidism in grown-up congenital heart disease patients

Subclinical hypothyroidism usually is asymptomatic, but it can be associated with various adverse cardiologic outcomes. With the objective of gaining insight into the role of thyroid-stimulating hormone (TSH) in congenital heart abnormalities, this study measured serum TSH concentrations in different subtypes of grown-up congenital heart disease (GUCHD) patients. Serum TSH (reference range, 0.34-5.6 mIU/L), creatinine, cholesterol, C-reactive protein (CRP), N-terminal proB-type natriuretic peptide (NT-pro-BNP), and 24-h proteinuria were measured in 249 GUCHD patients. Of 24 GUCHD patients (9.6 %) with a TSH level higher than 5.6 mUI/L, nine were cyanotic (37.5 %) and seven (29.1 %) had Down syndrome. The GUCHD patients with serum TSH exceeding 5.6 mIU/L had a significantly higher level of serum NT-pro-BNP (195.1 [0.28; 5,280.3] vs 57.6 [0.00; 929.8]; p = 0.001) and CRP (0.30 [0.06; 1.87] vs 0.16 [0.00; 1.40]; p = 0.011] than those with a TSH level of 5.6 mIU/L or lower. No significant differences were found in serum creatinine, lipids, or 24-h proteinuria between the two groups. The T4 concentrations in the GUCHD patients with TSH exceeding 5.6 mIU/L were within the normal range (0.89 ± 0.23 ng/dL). In the multivariate analysis, cyanosis (odds ratio [OR], 6,399; 95 % confidence interval [CI] 2,296-17,830; p < 0.001), Down syndrome (OR, 6,208; 95 % CI, 1,963-19,636; p = 0.002), and NT-pro-BNP concentrations (OR, 1,001; 95 % CI, 1,000-1,002; p < 0.026) proved to be risk factors for TSH levels higher than 5.6 mIU/L. Because subclinical hypothyroidism entails a cardiovascular risk, the authors postulate that TSH screening should be included in the routine follow-up evaluation of GUCHD patients with cyanosis or Down syndrome.

Hypothyroidism compromises hypothalamic leptin signaling in mice

The impact of thyroid hormone (TH) on metabolism and energy expenditure is well established, but the role of TH in regulating nutritional sensing, particularly in the central nervous system, is only poorly defined. Here, we studied the consequences of hypothyroidism on leptin production as well as leptin sensing in congenital hypothyroid TRH receptor 1 knockout (Trhr1 ko) mice and euthyroid control animals. Hypothyroid mice exhibited decreased circulating leptin levels due to a decrease in fat mass and reduced leptin expression in white adipose tissue. In neurons of the hypothalamic arcuate nucleus, hypothyroid mice showed increased leptin receptor Ob-R expression and decreased suppressor of cytokine signaling 3 transcript levels. In order to monitor putative changes in central leptin sensing, we generated hypothyroid and leptin-deficient animals by crossing hypothyroid Trhr1 ko mice with the leptin-deficient ob/ob mice. Hypothyroid Trhr1/ob double knockout mice showed a blunted response to leptin treatment with respect to body weight and food intake and exhibited a decreased activation of phospho-signal transducer and activator of transcription 3 as well as a up-regulation of suppressor of cytokine signaling 3 upon leptin treatment, particularly in the arcuate nucleus. These data indicate alterations in the intracellular processing of the leptin signal under hypothyroid conditions and thereby unravel a novel mode of action by which TH affects energy metabolism.

AdipoR1 and AdipoR2 gene expression are regulated by thyroid hormones in adipose tissue

The aim of this study was to examine whether the relative gene expression of AdipoR1 and AdipoR2 in rat adipose tissue is altered by thyroid hormones, and whether this might relate to their circulating thyroid hormones and adiponectin levels. Hyper- and hypothyroidism were induced by daily oral administration of levothyroxine and methimazole in rats, respectively, over a 42 days period. Real-time PCR analysis was performed to evaluate the changes in AdipoR1 and AdipoR2 mRNA levels in the adipose tissue on days 15, 28, 42, and also 2 weeks after the cessation of treatment. In response to treatment with methimazole, mRNA levels of AdipoR1 and AdipoR2 decreased in the white adipose tissue compared to the euthyroid rats (p < 0.05). This decline was reversible 2 weeks after treatment cessation. The mRNA levels of AdipoR1 and AdipoR2 were increased in the hyperthyroid group of animals compared to euthyroid control (p < 0.05), and its changes were reversible 2 weeks after treatment cessation (P < 0.05). Adiponectin receptors gene expression levels in the adipose tissue of treated animals have positive correlations with thyroid hormones concentrations. Our results suggest that AdipoR1 and AdipoR2 gene expression is regulated by thyroid hormones in hypo- and hyperthyroidism.

Adiposity blunts the positive relationship of thyrotropin with proprotein convertase subtilisin-kexin type 9 levels in euthyroid subjects

BACKGROUND

Effects of thyroid function status on lipoprotein metabolism may extend into the euthyroid range. Low-density lipoprotein (LDL) metabolism is governed by proprotein convertase subtilisin-kexin type 9 (PCSK9), which down-regulates LDL receptor expression, resulting in higher LDL cholesterol (LDL-C). Here, we tested whether plasma PCSK9 correlates with thyroid function in nonobese and obese euthyroid subjects.

METHODS

We assessed the extent to which plasma PCSK9 is determined by thyrotropin (TSH) in 74 euthyroid subjects (31 women; TSH between 0.5 and 4.0 mU/L and free thyroxine [FT4] between 11.0 and 19.5 pM) with varying degrees of obesity (body mass index [BMI] ranging from 20.2 to 40.4 kg/m(2)).

RESULTS

TSH, FT4, PCSK9, non-high-density lipoprotein cholesterol (non-HDL-C), LDL-C, and apolipoprotein B (apoB) levels were not different between 64 nonobese subjects (BMI<30 kg/m(2)) and 10 obese subjects (BMI≥30 kg/m(2); p>0.20 for each). PCSK9 correlated positively with TSH in nonobese subjects (r=0.285, p=0.023). In contrast, PCSK9 was not associated positively with TSH in obese subjects (r=-0.249, p=0.49). The relationship of PCSK9 with TSH was different between nonobese and obese subjects when taking age, sex, FT4, and the presence of anti-thyroid antibodies into account (multiple linear regression analysis: β=-0.320, p=0.012 for the interaction term between the presence of obesity and TSH on PCSK9), and was also modified by BMI as a continuous trait (β=-0.241, p=0.062 for the interaction term between BMI and TSH on PCSK9). Non-HDL-C, LDL-C, and apoB levels were dependent on PCSK9 in nonobese subjects (p≤0.01 for each), but not in obese subjects (p>0.50), Accordingly, BMI interacted negatively with PCSK9 on non-HDL-C (p=0.028) and apoB (p=0.071).

CONCLUSIONS

This study suggests that circulating PCSK9 levels correlate with thyroid function even in the normal range. This relationship appears to be blunted by obesity. Thyroid functional status may influence cholesterol metabolism through the PCSK9 pathway.

Subclinical hypothyroidism after vascular complicated pregnancy

OBJECTIVE

Women with a history of vascular complicated pregnancy are at risk for developing remote cardiovascular disease. It is associated with underlying cardiovascular risk factors both jeopardizing trophoblast and vascular function. Subclinical hypothyroidism may relate to both conditions.

METHODS

In 372 women with a history of vascular complicated pregnancy, we assessed thyroid function.

RESULTS

Subclinical hypothyroidism was diagnosed in 73/372 women (19.6%). It occurred more often when pregnancy ended before 32 weeks of gestation (p = 0.008).

CONCLUSION

In this cohort, subclinical hypothyroidism is more common after very preterm delivery. It may contribute to the elevated risk of remote cardiovascular disease.

Using body mass index to predict optimal thyroid dosing after thyroidectomy

BACKGROUND

Current postoperative thyroid replacement dosing is weight based, with adjustments made after thyroid-stimulating hormone values. This method can lead to considerable delays in achieving euthyroidism and often fails to accurately dose over- and underweight patients. Our aim was to develop an accurate dosing method that uses patient body mass index (BMI) data.

STUDY DESIGN

A retrospective review of a prospectively collected thyroid database was performed. We selected adult patients undergoing thyroidectomy, with benign pathology, who achieved euthyroidism on thyroid hormone supplementation. Body mass index and euthyroid dose were plotted and regression was used to fit curves to the data. Statistical analysis was performed using STATA 10.1 software (Stata Corp).

RESULTS

One hundred twenty-two patients met inclusion criteria. At initial follow-up, only 39 patients were euthyroid (32%). Fifty-three percent of patients with BMI >30 kg/m(2) were overdosed, and 46% of patients with BMI <25 kg/m(2) were underdosed. The line of best fit demonstrated an overall quadratic relationship between BMI and euthyroid dose. A linear relationship best described the data up to a BMI of 50. Beyond that, the line approached 1.1 μg/kg. A regression equation was derived for calculating initial levothyroxine dose (μg/kg/d = -0.018 × BMI + 2.13 [F statistic = 52.7, root mean square error of 0.24]).

CONCLUSIONS

The current standard of weight-based thyroid replacement fails to appropriately dose underweight and overweight patients. Body mass index can be used to more accurately dose thyroid hormone using a simple formula.

Adiposopathy and thyroid disease: tracing the pathway to cardiovascular risk

Adiposopathy, defined as functionally disturbed adipose tissue mainly composed of large adipocytes and induced by chronic excess of food intake, has been associated with immune, metabolic and endocrine derangements promoting inflammation and, eventually, cardiovascular disease. Adiposopathy may positively influence thyrotropin-stimulating hormone, by raising leptin levels, and triggering autoimmunity. In this regard, it is hypothesized that the increased thyrotropin-stimulating hormone is independent of the negative regulation of the thyroid hormone, thereby constituting a secondary phenomenon and not a causal effect. Replacement therapy with thyroid hormones should therefore be applied following strict individualized consideration. Leptin is involved in the immune response and neuroendocrine appetite regulation, while leptin resistance may further promote autoimmune disease. The lipid derangement in adiposopathy may be aggravated in the presence of hypothyroidism and thus considerably augment cardiovascular risk. Lifestyle-modification counselling, including low-fat dietary intake and regular physical exercise, is today the cornerstone of adiposopathy treatment. Meanwhile, new drug formulations, such as leptin and leptin analogs, 5-HT2C-receptor agonist, and potent thyromimetics, currently comprise a promising armamentarium against adiposity and adiposopathy.

Human stearoyl-CoA desaturase 1 (SCD-1) gene expression is negatively regulated by thyroid hormone without direct binding of thyroid hormone receptor to the gene promoter

Stearoyl-CoA desaturase-1 (SCD-1) plays a pivotal role in an increase of triglyceride by an excess of dietary carbohydrate intake. Dietary carbohydrates increase SCD-1 gene expression in liver by sterol response element binding protein (SREBP)-1c-dependent and SREBP-1c -independent pathways. Previous report demonstrated that thyroid hormone (TH) negatively regulates mouse SCD-1 gene promoter before SREBP-1c was revealed. We reported that TH negatively regulates SREBP-1c recently. Therefore, in the current study, we examined whether and how TH regulates human SCD-1 gene expression and evaluated SREBP-1c effect on the negative regulation. Luciferase assays revealed that TH suppresses both mouse and human SCD-1 gene promoter activity. In SREBP-1 knockdown HepG2 cells, TH still suppresses SCD-1 gene promoter activity, and it also exerted the negative regulation under cotransfection of a small amount of SREBP-1c. These data indicated that SREBP-1c does not play the decisive role for the negative regulation by TH. The responsible region for the negative regulation in human SCD-1 gene promoter turned out to be between -124 and -92 bp, referred to as site A. Chromatin immunoprecipitation assays demonstrated that TH receptor-β is recruited to the region upon T(3) administration, although TR-β does not bind directly to site A. In conclusion, TH negatively regulates human SCD-1 gene expression in without direct binding of the TH receptor to the SCD-1 gene promoter.

Association between novel adipocytokines adiponectin, vaspin, visfatin, and thyroid: An experimental and clinical update

Adipose tissue secretes a variety of active biological substances, called adipocytokines, that act in an autocrine, paracrine, and endocrine manner. They have roles in appetite control, thermogenesis, and thyroid and reproductive functions. All these molecules may lead to local and generalized inflammation, mediating obesity-associated vascular disorders including hypertension, diabetes, atherosclerosis, and insulin resistance. Thyroid dysfunction is associated with changes in body weight, thermogenesis, and energy expenditure. The connections between cardiovascular risk factors such as dyslipidemia, impaired glucose tolerance, insulin resistance, atherosclerosis, and thyroid dysfunction have been reported in several studies. The adipocytokines serve as causative or protective factors in the development of these disorders in the states of thyroid dysfunction. Abnormal levels of adipocytokines (adiponectin (ADP), leptin, resistin, vaspin, and visfatin) in hypo- and hyperthyroidism have been reported with controversial results. This review aims to update the implication of novel adipokines ADP, vaspin, and visfatin in thyroid dysfunction.

The contribution of thyroid dysfunction on cardiovascular disease in patients with chronic kidney disease

Accelerated atherosclerosis and arterial stiffness are the two leading causes of increased cardiovascular disease in patients with chronic kidney disease. Dysfunctional thyroid hormone metabolism has been suggested to play a role in atherosclerosis and arterial stiffness. Changes in cardiac contractility and output, myocardial oxygen demand, systemic and peripheral vascular resistance, blood pressure and lipid profile, increased inflammatory burden and endothelial dysfunction may be responsible for thyroid hormone-related cardiovascular disease. This article focuses on the mechanistic insights of this association and provides a concise review of the current literature.

Age and gender substantially influence the relationship between thyroid status and the lipoprotein profile: results from a large cross-sectional study

BACKGROUND

Conflicting data are reported on the association between mild thyroid failure and lipid profile, primarily regarding serum triglyceride values and patients with slightly elevated thyrotropin (TSH, <10 mIU/L). In this study, we assessed the possible influence of gender and age on this relationship.

METHODS

The study included 2308 consecutive patients who were seen for suspected or diagnosed thyroid disease (1874 women, 434 men, mean age 47.5±14.1 and 46.9±14.0 years, respectively) and on whom studies of thyroid status and lipoprotein profile were conducted after an overnight fast. Patients with uncontrolled diabetes mellitus and those taking lipid-lowering drugs were excluded.

RESULTS

There were 628 patients receiving L-thyroxine who had a diagnosis of hypothyroidism: 200 were hyperthyroid, and 120 were still hypothyroid. Overall, 648 patients were hypothyroid, and 290 were hyperthyroid. No gender difference in the frequency of TSH values in the ranges studied (i.e., TSH frequency distribution) was observed. Total cholesterol (TC) and low-density lipoprotein cholesterol (LDLc) values (p<0.0003 and p<0.003, respectively) as well as the LDL/high-density lipoprotein cholesterol (HDLc) ratio (p<0.03) were elevated not only in unselected women with TSH values in the 4th TSH group (>10 mIU/L) but also in those of the 3rd group (3.6-10.0 mIU/L) who were older than 50 years (TC and LDLc p=0.01, LDL/HDLc ratio p=0.02 vs. euthyroid women). Among unselected men, only those of the 4th TSH group had elevated triglyceride (p<0.0001) but not cholesterol values. However, men of the 3rd and 4th TSH group who were older than 65 years had significantly higher TC, LDLc, and LDL/HDLc values as well (p=0.03, p=0.02 and p=0.01, respectively vs. euthyroid men). In the final model of stepwise regression for predicting each lipid parameter variation on the basis of age, TSH, free thyroxine (FT4), and body mass index (BMI) analysis, age had the highest standardized coefficient (0.36 and 0.37, respectively), followed by TSH (0.20 and 0.11, respectively) and FT4 (-0.11 and -0.09, respectively) when looking at TC and LDLc; whereas BMI had the highest standardized coefficient (0.28), followed by age (0.15) and TSH (0.11) when looking at triglyceride variation.

CONCLUSIONS

This study confirms a gender differentiation in the relationship between hypothyroidism and the lipid profile, which is substantially influenced by age, especially in patients with mild thyroid impairment (TSH<10 mIU/L).

Postprandial hyperlipidemia in overt and subclinical hypothyroidism

BACKGROUND AND AIMS

Lipid alterations in overt hypothyroidism (OH) were well known, but its changes in subclinical hypothyroidism (SCH) and postprandial period were not clear. The aim of this study is to evaluate postprandial lipemia by oral lipid tolerance test (OLTT) in patients with OH and SCH.

MATERIALS AND METHODOLOGY

Twenty-five OH and 27 SCH, totally 52 hypothyroid patients [mean age 38.3 ± 12.8 year, body mass index (BMI): 29.0 ± 5.8 kg/m(2)] and 23 BMI- and age-matched healthy controls (mean age 36.7 ± 11.9 years; BMI: 27.1 ± 6.9 kg/m(2)) were included to the study. Anthropometric measurements and HOMA-IR levels were measured. Basal and postprandial lipid profile at 2nd, 4th, 6th and 8th hours were determined by oral lipid tolerance test.

RESULTS

There were not any statistical differences among three groups (control, OH and SCH) in terms of mean fasting levels of total cholesterol, LDL-cholesterol, VLDL-cholesterol, and triglyceride. On the contrary, mean triglyceride levels at postprandial 8th hour in both OH and SCH patients were higher than control subjects (p=0.017 and p=0.049, respectively). Again mean postprandial 8th hour VLDL-cholesterol levels in OH group were also higher than control subjects (p=0.05). In addition mean HOMA-IR value of SCH and OH patients was similar with control subjects (1.5 ± 1.4 in OH; 1.3 ± 0.8 in SCH; 2.2 ± 2.2 in control group).

CONCLUSIONS

Although total, LDL and VLDL-cholesterol, and triglyceride levels were not different from healthy controls, triglyceride and/or VLDL-cholesterol levels apparently increased with OLTT in both OH and SCH patients. Decreased lipid clearance may be responsible for this result.

Insulin sensitivity modifies the relationship between thyroid function and lipid profile in euthyroid type 1 diabetic patients

It has been suggested that association between hypothyroidism with dyslipidemia might be present already at the stage of normal thyroid function through altered insulin sensitivity. We analyzed the role of insulin sensitivity as a mediator of thyroid-induced lipid changes in euthyroid type 1 diabetic patients. Study included 304 patients with type 1 diabetes and normal thyroid function. Insulin sensitivity was measured with estimated glucose disposal rate calculated using the equation: eGDR = 24.31 - (12.22 × WHR) - (3.29 × HT) - (0.57 × HbA1c); WHR = waist-to-hip ratio, HT = hypertension. TSH, FT4, FT3, and serum lipids were measured. Correlations and multiple linear regressions analysis were performed to identify relationships between thyroid status and serum lipid parameters after stratifying patients in quartiles of eGDR. After adjustment for age, sex, BMI, duration of diabetes and insulin dose TSH, FT3, and FT4 was not significantly associated with serum lipids in all patients, independently of level of insulin sensitivity. However, after stratifying patients for the degree of insulin sensitivity in subjects in the lowest quartile of insulin sensitivity TSH was independently associated with LDL cholesterol (β = 0.210, p = 0.02). The independent relation of eGDR with TSH and LDL cholesterol suggests that the influence of thyroid function on lipid metabolism might extend into euthyroid range through altered insulin sensitivity.

Are hsCRP Levels and LDL/HDL Ratio Better and Early Markers to Unmask Onset of Dyslipidemia and Inflammation in Asymptomatic Subclinical Hypothyroidism?

The implications of subclinical hypothyroidism (SCH) are many amongst which the most important is progression to overt hypothyroidism. Other debatable aspects are its association with cardiovascular risk, neuromuscular and psychiatric dysfunction, increased predisposition to developing metabolic syndrome and an underlying pro-inflammatory state. We aimed to study the lipid profile, lipoprotein(a) [Lp(a)] and hsCRP levels and insulin resistance in a group of patients with SCH in a referral hospital and see if any significant differences exist between them and euthyroids. This is a case-control study where the selection of controls and cases was based on the thyroid profile. Subjects were selected on their visit to clinical biochemistry lab for thyroid function tests. 33 euthyroids were taken as controls (Group I) and 38 patients comprising of subclinical hypothyroids were grouped as cases (Group II). Serum thyroid stimulating hormone (TSH) was in the range of 0.5-5.0 mIU/L for euthyroids and for subclinical hypothyroids the concentration of TSH was more than 5 mIU/L. The concentration of tri-iodothyronine (T3) and thyroxine (T4) were in normal reference range in both the groups. Individual lipid profile parameters failed to show a significant p value between cases and controls. The LDL/HDL ratio was highly significant (p value < 0.0001) and hsCRP was also statistically between the two groups (p value = 0.0054). Lp(a) and insulin resistance did not differ significantly. SCH is a common disorder that frequently progresses to overt hypothyroidism. This study underlines the importance of LDL/HDL ratio rather than measurement of individual lipid profile parameters in bringing to light the dyslipidemic state associated with SCH. Moreover the use of hsCRP to detect an underlying pro-inflammatory state in SCH can also be emphasized.

Inverse association between serum free thyroxine levels and hepatic steatosis: results from the Study of Health in Pomerania

BACKGROUND

Associations between thyroid function and hepatic steatosis defined by enzymatic and sonographic criteria are largely unknown in the general population. Thus, the aim of the present study was to investigate the association between thyroid function tests and sonographic as well as enzymatic criteria of liver status in a large population-based study, the Study of Health in Germany (SHIP).

METHODS

Data from 3661 SHIP participants without a self-reported history of thyroid or liver disease were analyzed. Hepatic steatosis was defined as the presence of a hyperechogenic ultrasound pattern of the liver and increased serum alanine transferase concentrations. Serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) concentrations were associated with hepatic steatosis using multinomial regression models adjusted for sex, age, physical activity, alcohol consumption, waist circumference, and food intake pattern.

RESULTS

We detected no consistent association of serum TSH and FT3 concentrations with hepatic steatosis. In contrast, serum FT4 concentrations were inversely associated with hepatic steatosis in men (odds ratio (OR)=0.04 [95% confidence interval (CI)=0.01; 0.17]) and women (OR=0.06 [95% CI=0.01; 0.42]).

CONCLUSIONS

Results from the present cross-sectional study suggest that low FT4 concentrations are associated with hepatic steatosis. Longitudinal and intervention studies are warranted to investigate whether hypothyroidism increases the risk of hepatic steatosis or vice versa.

Thyroid stimulating hormone, independent of thyroid hormone, can elevate the serum total cholesterol level in patients with coronary heart disease: a cross-sectional design

Background

The relationship between TSH and the lipid profile is contradictory because few studies have excluded the potential influence of the thyroid hormones (TH). The aim of the present study was to evaluate the relationship between serum TSH levels and the lipid profile independent of TH.

Methods

1302 CHD patients diagnosed by coronary angiography were retrospectively studied. The prevalence and distribution of thyroid dysfunction were analyzed first. To assess the impact of TSH on serum lipids, Pearson’s correlation analysis was performed after adjustments for classic factors and TH. To calculate the extent of the effect of TSH on the serum cholesterol level, the partial least squares method and additional statistical methods were used.

Results

After the exclusions, a total of 568 patients (270 males and 298 females with a mean age of 63.56 ± 11.376 years) were selected. The prevalence of thyroid dysfunction among the patients was 18.66%, and the prevalence of hypothyroidism (15.32%) was higher than that of hyperthyroidism (3.34%). Even after adjusting for confounding factors, such as sex, age, smoking status, fasting plasma glucose levels and TH, a significant positive impact of TSH on the serum total cholesterol (TC) level was revealed (r = 0.095, p = 0.036). Each 1 mIU/L increase in the TSH level might be linked to a 0.015580712 mmol/L elevation of the serum TC value.

Conclusions

TSH can increase the TC level in CHD patients independent of TH. The present study suggests a potential physiological role of TSH and the importance of maintaining an appropriate TSH level in CHD patients.

Experimental hyperthyroidism decreases gene expression and serum levels of adipokines in obesity

Aims. To analyze the influence of hyperthyroidism on the gene expression and serum concentration of leptin, resistin, and adiponectin in obese animals. Main Methods. Male Wistar rats were randomly divided into two groups: control (C)—fed with commercial chow ad libitum—and obese (OB)—fed with a hypercaloric diet. After group characterization, the OB rats continued receiving a hypercaloric diet and were randomized into two groups: obese animals (OB) and obese with 25 μg triiodothyronine (T₃)/100 BW (OT). The T₃ dose was administered every day for the last 2 weeks of the study. After 30 weeks the animals were euthanized. Samples of blood and adipose tissue were collected for biochemical and hormonal analyses as well as gene expression of leptin, resistin, and adiponectin. Results. T₃ treatment was effective, increasing fT₃ levels and decreasing fT₄ and TSH serum concentration. Administration of T₃ promotes weight loss, decreases all fat deposits, and diminishes serum levels of leptin, resistin, and adiponectin by reducing their gene expression. Conclusions. Our results suggest that T₃ modulate serum and gene expression levels of leptin, resistin, and adiponectin in experimental model of obesity, providing new insights regarding the relationship between T₃ and adipokines in obesity.

The metabolic syndrome in thyroid disease: A report from Nigeria

BACKGROUND

The objective of this study was to determine the prevalence of the metabolic syndrome and its components in people with thyroid disorders.

MATERIALS AND METHODS

112 subjects with a history of thyroid disorders were consecutively enrolled for the study. Clinical data were obtained by interviewing the patients and referring to their case folders and prescriptions. The subjects were categorized into three: thyrotoxic, those with hypothyroidism and those with nontoxic goiters, based on clinical parameters and or thyroid function tests. The study subjects were weighed and their anthropometric indices were documented. The laboratory parameters that were analyzed included total cholesterol, high-density and low-density cholesterol and triglyceride. Statistical analysis was performed using Student's t test, one-way analysis of variance (ANOVA) test and chi-square test.

RESULTS

The study subjects were aged between 14 and 76 years, with a mean age of 44.5 years, and the female:male ratio was 97:15. The mean age and anthropometric indices were comparable in subjects with thyrotoxicosis, hypothyroidism and euthyroidism. The overall prevalence of the metabolic syndrome was 28% and the frequency of occurrence of the metabolic syndrome in subjects with thyrotoxicosis, hypothyroidism and nontoxic goiter was 24%, 40% and 42%, respectively. The commonest occurring metabolic syndrome defining criterion was dysglycemia, while hypertension and elevated triglyceride were the least documented of the criteria.

CONCLUSION

Metabolic syndrome occurs in 1 in every 4 persons with thyroid disorders, and as such, routine screening for this cardiovascular risk factor may be of benefit in this group of people, especially in those with hypothyroidism.

Metabolic effects of the iodothyronine functional analogue TRC150094 on the liver and skeletal muscle of high-fat diet fed overweight rats: an integrated proteomic study

A novel functional iodothyronine analogue, TRC150094, which has a much lower potency toward thyroid hormone receptor (α1/β1) activation than triiodothyronine, has been shown to be effective at reducing adiposity in rats simultaneously receiving a high-fat diet (HFD). Here, by combining metabolic, functional and proteomic analysis, we studied how the hepatic and skeletal muscle phenotypes might respond to TRC150094 treatment in HFD-fed overweight rats. Drug treatment increased both the liver and skeletal muscle mitochondrial oxidative capacities without altering mitochondrial efficiency. Coherently, in terms of individual respiratory in-gel activity, blue-native analysis revealed an increased activity of complex V in the liver and of complexes II and V in tibialis muscle in TCR150094-treated animals. Subsequently, the identification of differentially expressed proteins and the analysis of their interrelations gave an integrated view of the phenotypic/metabolic adaptations occurring in the liver and muscle proteomes during drug treatment. TRC150094 significantly altered the expression of several proteins involved in key liver metabolic pathways, including amino acid and nitrogen metabolism, and fructose and mannose metabolism. The canonical pathways most strongly influenced by TRC150094 in tibialis muscle included glycolysis and gluconeogenesis, amino acid, fructose and mannose metabolism, and cell signaling. The phenotypic/metabolic influence of TRC150094 on the liver and skeletal muscle of HFD-fed overweight rats suggests the potential clinical application of this iodothyronine analogue in ameliorating metabolic risk parameters altered by diet regimens.

Are serum TSH levels associated with oxidized low-density lipoprotein? Results from the Study of Health in Pomerania

OBJECTIVE

Oxidized LDL (oxLDL) is involved in the pathogenesis of atherosclerosis. Thus, it is important to investigate putative risk factors for increased oxLDL. Evidence suggests that, compared to euthyroid individuals, LDL-cholesterol (LDL-C) levels are lower in individuals with overt hyperthyroidism. Whereas oxidization of LDL-C into oxLDL is increased in overt hyper- and hypothyroidism, it has not been investigated whether subclinical thyroid dysfunction impacts on oxLDL levels in general. We have analysed the association between serum thyrotrophin (TSH) levels and oxLDL in a population-based study.

DESIGN, PATIENTS AND MEASUREMENTS

Of the 4308 individuals enrolled in the Study of Health in Pomerania, data from 3519 individuals were analysed (680 missing the oxLDL variable). oxLDL was measured by the oxLDL competitive ELISA on a BEP 2000. Multivariable linear regression models were performed to assess the association between serum TSH and oxLDL levels.

RESULTS

TSH was positively associated with oxLDL in a curvilinear fashion with increasing serum TSH levels. Subgroup analyses revealed a significant association only in the group of individuals >60 years. Additionally, serum TSH levels were not associated with the ratio of oxLDL to LDL (β = -0·04; 95% CI = -0·08, 0·01; P = 0·084).

CONCLUSIONS

We demonstrate an association between serum TSH and oxLDL levels especially in the range of subclinical thyroid disease. Our study suggests that serum TSH levels affect LDL-C production or clearance rather than the LDL-C oxidation processes.

A high normal TSH level is associated with an atherogenic lipid profile in euthyroid non-smokers with newly diagnosed asymptomatic coronary heart disease

Background

Serum lipid profiles may be influenced by thyroid function, but the detailed mechanism remains unclear. Increasing evidence suggests that thyrotropin (TSH) may exert extra-thyroidal effects. The goal of this study was to evaluate the relationship between serum TSH levels and the lipid profiles in euthyroid non-smokers with newly diagnosed asymptomatic coronary heart disease (CHD).

Methods

This was a retrospective study of 406 euthyroid non-smokers (187 males and 219 females) with newly diagnosed asymptomatic CHD from 2004 to 2010 in Jinan, China. Lipid parameters and the levels of TSH, FT3, and FT4 were determined. Multiple linear regression analysis and Logistic regression analysis were used to assess the influence of TSH on the lipid profiles and the risks of dyslipidemia.

Results

The TSH level, even within the normal range, was positively and linearly correlated with total cholesterol (TC), non-high density lipoprotein cholesterol (non-HDL-C) and triglycerides (TG) (Beta = 0.173, 0.181 and 0.103, respectively, P < 0.01 in all). With 1 mIU/L rise of TSH, the levels of TC, TG and non-HDL-C will increase by 1.010, 1.064, and 1.062 mmol/L, respectively. The odds ratio of hypercholesterolemia and hypertriglyceridemia with respect to the serum TSH level was 1.640 (95% CI 1.199-2.243, P = 0.002) and 1.349 (95% CI 1.054-1.726, P = 0.017), respectively.

Conclusions

TSH levels were correlated in a positive linear manner with the TC, non-HDL-C and TG levels in euthyroid non-smokers with newly diagnosed asymptomatic CHD. TSH in the upper limits of the reference range might exert adverse effects on lipid profiles and thus representing as a risk factor for hypercholesterolemia and hypertriglyceridemia in the context of CHD.

Hypothyroidism: etiology, diagnosis, and management

Hypothyroidism is the result of inadequate production of thyroid hormone or inadequate action of thyroid hormone in target tissues. Primary hypothyroidism is the principal manifestation of hypothyroidism, but other causes include central deficiency of thyrotropin-releasing hormone or thyroid-stimulating hormone (TSH), or consumptive hypothyroidism from excessive inactivation of thyroid hormone. Subclinical hypothyroidism is present when there is elevated TSH but a normal free thyroxine level. Treatment involves oral administration of exogenous synthetic thyroid hormone. This review presents an update on the etiology and types of hypothyroidism, including subclinical disease; drugs and thyroid function; and diagnosis and treatment of hypothyroidism.

The effect of thyroid disorders on lipid levels and metabolism

Thyroid hormones regulate cholesterol and lipoprotein metabolism, whereas thyroid disorders, including overt and subclinical hypothyroidism, considerably alter lipid profile and promote cardiovascular disease. Good evidence shows that high thyroid-stimulating hormone (TSH) is associated with a nonfavorable lipid profile, although TSH has no cutoff threshold for its association with lipids. Thyromimetics represent a new class of hypolipidemic drugs: their imminent application in patients with severe dyslipidemias, combined or not with statins, will improve the lipid profile, potentially accelerate energy expenditure and, as a consequence, vitally lessen the risk of cardiovascular disease.

Subclinical hypothyroidism and hyperthyroidism have opposite effects on hepatic very-low-density lipoprotein-triglyceride kinetics

CONTEXT

Clinically overt thyroid dysfunction is associated with alterations in triglyceride (TG) metabolism. The effect of subclinical thyroid disease on very-low-density lipoprotein (VLDL) kinetics is not known.

OBJECTIVE

Our objective was to investigate whether subclinical thyroid disease is associated with alterations in hepatic VLDL metabolism. DESIGN AND OUTCOMES: We measured VLDL-TG and VLDL-apolipoprotein B-100 (apoB-100) kinetics by infusing stable isotopically labeled tracers, in conjunction with mathematical modeling.

SETTING AND PARTICIPANTS

Ten women with subclinical hypothyroidism, 10 women with subclinical hyperthyroidism, and 25 euthyroid women, matched on age, body mass index, and percent body fat, were studied in the Clinical Research Unit at Washington University School of Medicine.

RESULTS

Plasma VLDL-TG concentrations were 0.75±0.13, 0.51±0.06, and 0.37±0.07 mmol/liter (P=0.029), and hepatic VLDL-TG secretion rates were 6.5±0.7, 5.0±0.4, and 4.1±0.6 μmol/liter·min (P=0.026) in hypothyroid, euthyroid, and hyperthyroid women, respectively. The differences in VLDL-TG secretion rates were due to differences in the incorporation of systemic plasma free fatty acids into VLDL-TG (4.3±0.3, 3.1±0.3, and 2.5±0.3 μmol/liter·min in hypothyroid, euthyroid, and hyperthyroid women, respectively; P=0.005). Plasma VLDL-apoB-100 concentration and hepatic secretion rate did not differ among groups (P>0.400), so the molar ratios of VLDL-TG to VLDL-apoB-100 secretion rates were 21,469±3,477, 16,025±1,273, and 11,889±1,319 in hypothyroid, euthyroid, and hyperthyroid women, respectively (P=0.019).

CONCLUSIONS

Subclinical thyroid disease affects hepatic VLDL-TG but not VLDL-apoB-100 metabolism: subclinical hypothyroidism increases, whereas subclinical hyperthyroidism decreases, hepatic VLDL-TG secretion rate compared with the euthyroid state. Plasma VLDL-TG concentration is greater in subclinical hypothyroid than euthyroid and hyperthyroid subjects, due to greater secretion of large, TG-rich VLDL particles from the liver.

A review on cardiovascular diseases originated from subclinical hypothyroidism

Thyroid hormones play an important role on the cardiovascular systems and thyroid disorder ultimately have a profound adverse effects on myocardium and vascular functions. There are extensive reports on the role of overt thyroid dysfunction which adversely can modify the cardiovascular metabolism but even at the present of some controversial reports, the subclinical thyroid disorders are able also to manipulate cardiovascular system to some extent. The aim of this study is to review the cardiovascular disorders accompanied with subclinical hypothyroidism. It is concluded that adverse effect of thyroid malfunction on myocardium and vascular organs are through the direct role of thyroid hormone and dyslipidemia on heart muscle cells at nuclear level and vascular system, respectively. It seems many cardiovascular disorders initially would not have been occurred in the first place if the thyroid of affected person had functioned properly, therefore thyroid function tests should be one of a prior laboratory examinations in cardiovascular disorders.

Blood lipid levels, lipid-lowering medications, and the incidence of atrial fibrillation: the atherosclerosis risk in communities study

BACKGROUND

Several cardiovascular risk factors have been associated with the risk of atrial fibrillation (AF). Limited and inconsistent evidence exists on the association of blood lipid levels and lipid-lowering medication use with AF risk.

METHODS AND RESULTS

We analyzed 13 969 participants (25% African American, 45% men) free of AF at baseline from the Atherosclerosis Risk in Communities study. Fasting high-density lipoprotein cholesterol (HDLc), low-density lipoprotein cholesterol (LDLc), triglycerides, and total cholesterol were measured at baseline (1987-1989) and each of 3 follow-up visits. The incidence of AF was ascertained through 2007. The association of the use of statins and other lipid-lowering medications with AF was estimated in 13 044 Atherosclerosis Risk in Communities participants attending visit 2 (1990-1992), adjusting for covariates from the previous visit. During a median follow-up of 18.7 years, there were 1433 incident AF cases. Multivariable hazard ratios (HRs) and 95% CIs of AF associated with a 1-SD increase in lipid levels were as follows: HDLc, 0.97 (0.91-1.04); LDLc, 0.90 (0.85-0.96); total cholesterol, 0.89 (0.84-0.95); and triglycerides, 1.00 (0.96-1.04). Participants taking lipid-lowering medications had an adjusted HR (95% CI) of AF of 0.96 (0.82-1.13) compared with those not taking medications, whereas those taking statins had an adjusted HR of 0.91 (0.66-1.25) compared with those taking other lipid-lowering medications.

CONCLUSIONS

Higher levels of LDLc and total cholesterol were associated with a lower incidence of AF. However, HDLc and triglycerides were not independently associated with AF incidence. No association was found between the use of lipid-lowering medications and incident AF.

Nutritional and hormonal modulation of adiponectin and its receptors adipoR1 and adipoR2

Adiponectin is the most abundant plasma protein synthesized mostly by adipose tissue and is an insulin-sensitive hormone, playing a central role in glucose and lipid metabolism. Adiponectin effects are mediated via two receptors, adipoR1 and adipoR2. Several hormones and diet components that are involved in insulin resistance may impair insulin sensitivity at least in part by decreasing adiponectin and adiponectin receptors. Adiponectin expression and serum levels are associated with the amount and type of fatty acids and carbohydrate consumed. Other food items, such as vitamins, alcohol, sodium, green tea, and coffee, have been reported to modify adiponectin levels. Several hormones, including testosterone, estrogen, prolactin, glucocorticoids, catecholamines, and growth hormone, have been shown to inhibit adiponectin production, but the studies are still controversial. Even so, adiponectin is a potential therapeutic target in the treatment of diabetes mellitus and other diseases associated with hypoadiponectinemia.

Serum TSH level in healthy Koreans and the association of TSH with serum lipid concentration and metabolic syndrome

BACKGROUND/AIMS

The proper treatment of subclinical hypothyroidism and the normal range of serum thyroid stimulating hormone (TSH) concentration are intensely debated. However, few reports have investigated TSH concentrations in Asian ethnic groups. Therefore, the present study was designed to define the TSH reference range in a Korean population and to investigate the metabolic significance of TSH concentration.

METHODS

We enrolled patients who underwent medical examination at the CHA Bundang Medical Center. Anthropometric data were evaluated, and serum TSH, free T4, and lipid profiles were assayed.

RESULTS

A total of 7,270 subjects were included. Mean TSH concentration of the study population was 1.82 ± 0.95 mU/L, and we observed a sex-related difference in TSH concentration (male, 1.67 ± 0.87 mU/L; female, 2.02 ± 1.01 mU/L; p < 0.01). When the 2.5 and 97.5 percentiles were calculated, 95% TSH reference limits were 0.52-4.29 mU/L. TSH concentration was higher in elderly subjects, during winter, in postmenopausal women, and in obese males. Moreover, TSH showed significantly positive correlations with serum total cholesterol, triglyceride, and low density lipoprotein cholesterol regardless of sex, age, season, obesity, or menopausal status (all p < 0.01). Finally, TSH concentration was positively related to the prevalence of metabolic syndrome.

CONCLUSIONS

We demonstrated the association between TSH concentration within the normal reference range and serum lipid levels. TSH concentration varies according to sex, age, season, and body mass index (only in males). Moreover, high normal TSH levels were significantly associated with an increased prevalence of metabolic syndrome, which may be of importance when evaluating subjects with high normal TSH concentration.

Association between Perchlorate and Indirect Indicators of Thyroid Dysfunction in NHANES 2001-2002, a Cross-Sectional, Hypothesis-Generating Study

BACKGROUND

A previous study based on NHANES 2001-2002 observed that increased levels of urinary perchlorate were associated with increased levels of thyroid stimulating hormone among all women, and with decreased levels of thyroxine among women with low urinary iodine. No associations were observed for men.

METHODS

Using the same NHANES 2001-2002 data, associations of urinary perchlorate with indirect biomarkers of thyroid hormone disruption were investigated. Decreased levels of hemoglobin (HGB), hematocrit (HCT), and high density lipoprotein (HDL) have been observed among subjects with subclinical hypothyroidism. To investigate the suitability of these indicators for use in observational studies, subjects were divided into six groups: boys, age 6-19; men, age 20-85; girls, age 6-14; non-pregnant women, age 15-49; women, age 50-85; and pregnant women. Use of perchlorate quintiles (Q1-Q5) and continuous log-transformed perchlorate in the regression models allowed investigation of both non-linear and linear associations. Adjustments were made for age, urinary creatinine, race/ethnicity, body mass index, cotinine, poverty index, hours of fasting, thiocyanate, nitrate, daily kcal intake, C-reactive protein. Adjustment for alcohol consumption depended on availability. Adjustment for prescription drugs (beta-blockers, sex hormones, antihyperlipidemic and antidiabetic drugs) was made if it changed the perchlorate estimate by ≥10%.

RESULTS

Statistically significant decreases were observed for HGB and HCT among boys, men, women age 15-49, and pregnant women, and for HDL among men.

CONCLUSIONS

Although the mean response biomarkers were within normal range, their association with urinary perchlorate is of interest. HGB and HCT among pregnant women showed a stronger association with urinary perchlorate than non-pregnant women age 15-49. Statistically significant associations were observed for individual perchlorate quintiles. Assumption of linearity of log-transformed perchlorate may result in underestimation of some associations.

Thyroid function in childhood obesity and metabolic comorbidity

Childhood obesity is a worldwide health problem and its prevalence is increasing steadily and dramatically all over the world. Obese subjects have a much greater likelihood than normal-weight children of acquiring dyslipidemia, elevated blood pressure, and impaired glucose metabolism, which significantly increase their risk of cardiovascular and metabolic diseases. Elevated TSH concentrations in association with normal or slightly elevated free T4 and/or free T3 levels have been consistently found in obese subjects, but the mechanisms underlying these thyroid hormonal changes are still unclear. Whether higher TSH in childhood obesity is adaptive, increasing metabolic rate in an attempt to reduce further weight gain, or indicates subclinical hypothyroidism or resistance and thereby contributes to lipid and/or glucose dysmetabolism, remains controversial. This review highlights current evidence on thyroid involvement in obese children and discusses the current controversy regarding the relationship between thyroid hormonal derangements and obesity-related metabolic changes (hypertension, dyslipidemia, hyperglycemia and insulin resistance, nonalcoholic fatty liver disease) in such population. Moreover, the possible mechanisms linking thyroid dysfunction and pediatric obesity are reviewed. Finally, the potential role of lifestyle intervention as well as of therapy with thyroid hormone in the treatment of thyroid abnormalities in childhood obesity is discussed.

Gluco-lipidic indices in treated hypothyroidism associated with nonalcoholic fatty liver disease

CONTEXT

Thyroid hormones may interfere with regulation of lipid and carbohydrate metabolism as well as with severity of nonalcoholic fatty liver disease (NAFLD), however results are still debated.

OBJECTIVES

Retrospective evaluation of clinical and metabolic correlations between hypothyroidism and NAFLD was the target.

METHODS

Clinical, biochemical and histological investigation of 103 NAFLD patients exhibiting drug-treated hypothyroidism was conducted.

RESULTS

Steatosis was present in 32.0% of the population and nonalcoholic steatohepatitis in 68.0%. Females were the majority in both groups, with age of 50.0 ± 1.5 and 56.0 ± 1.1 years, respectively. Hypothyroidism was not rare (15.5%), and multivariate analysis confirmed positive correlation with this disease for insulin (r = 0.213, P = 0.03), glucose homeostasis index "HOMA" (r = 0.221, P = 0.02), aspartate aminotransferase (r = 0.234, P = 0.01) and triglycerides above 150 mg/dL (r = 0.233, P = 0.01). No association between hypothyroidism and steatohepatitis could be established.

CONCLUSION

A link could be identified between hypothyroidism and markers of glucose and lipid homeostasis, but not with severity of NAFLD. The lack of correlation with liver biopsy requires further studies.