Hypothyroidism results in small dense LDL independent of IRS traits and hypertriglyceridemia

Conventional HDL Subclass Measurements Mask Thyroid Hormone-dependent Remodeling Activity Sites in Hypothyroid Individuals

Context

Earlier nuclear magnetic resonance spectroscopy (NMR) studies of plasma lipoproteins estimated by size as small, medium, and large particles, demonstrated hypothyroidism was associated with increases in very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and intermediate-density lipoprotein (IDL) subclass particle number but variable changes in the high-density lipoprotein (HDL) subclasses. These disparate changes in HDL might be explained by reduced activity of the thyroid hormone-dependent remodeling proteins whose subclass specificity may be obscured when the 5 HDL subclasses identified by NMR are combined by size.

Objective

This work aimed to determine whether directional changes in particle number of individually measured HDL subclasses correlate with reduced activity of their thyroid hormone-dependent remodeling proteins in hypothyroid individuals.

Methods

VLDL, LDL, IDL, and HDL subclasses were measured by NMR in 13 thyroidectomized individuals 1 month following thyroid hormone withdrawal and 3 months after replacement. Changes in particle numbers in each subclass were compared when expressed individually and by size.

Results

Following thyroid hormone withdrawal, plasma lipids and VLDL, LDL, and IDL subclass particle number increased. HDL particle number nearly doubled in very small HDL-1 (P = .04), declined in small HDL-2 (P = .02), and increased 2-fold in HDL-5 (P = .0009).

Conclusion

The increment in HDL-1 and decline in HDL-2 subclasses is consistent with their precursor-product relationship and reduced lecithin cholesterol acyltransferase activity while the almost 2-fold increase in large HDL-5 is indicative of diminished action of hepatic lipase, phospholipid transfer protein, and endothelial lipase. These findings are inapparent when the 5 subclasses are expressed conventionally by size. This linking of specific HDL subclasses with HDL remodeling protein function provides new details about the specificity of their interactions.

Misleading normal TSH and persistently elevated creatine kinase: clues to the diagnosis of chronic Sheehan's syndrome

A 53-year-old woman was referred for medical evaluation of therapy-resistant dyslipidaemia accompanied by elevated creatine kinase levels. Because cessation or alteration of her medication did not improve laboratory abnormalities, hypothyroidism was considered, despite the fact that thyroid stimulating hormone levels were within the reference interval. On further evaluation, she was found to have panhypopituitarism and empty sella turcica as shown by MRI. These findings were unexpected since there was no clinical suspicion during detailed evaluation. When supplementary questions were asked, she brought up a history of severe postpartum haemorrhage 30 years ago, for which she underwent a hysterectomy. Based on these findings, the patient was diagnosed with Sheehan's syndrome. This syndrome is a rare but potentially life-threatening complication of postpartum haemorrhage, characterised by varying degrees of hypopituitarism that are most commonly presented many years after delivery. The patient recovered after adequate hormone replacement therapy.

Visfatin, PON-1 Levels in Iraqi Hyperthyroidism Patient's with Dyslipidemia

In the study, it is aimed to research the likely role of visfatin in hyperthyroid and subclinical hyperthyroid status related to dislipidemia, after determining the visfatin and PON-1 levels thirty healthy individuals were enrolled in this study as control group and thirty hyperthyroidism patient's with dyslipidemia they were treated with. The subjects aged ranged (30-50) years and with BMI (25-29) kg/m². Serum was used in determination of lipid profile total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL), low density lipoprotein (LDL), very low density lipoprotein (VLDL), thyroid threonine (T3) and thyroxin (T4), thyroid stimulating hormone (TSH), visfatin and paraoxonase-1 (PON-1). The results showed significant increase in T3, T4, TC, TG, LDL and VLDL in patient group when comparing to control group. While significant decrease was found in TSH and HDL in patient group when comparing to control group. The results also represented significant increase in visfatin levels in patient group comparing to control group. While there are significant reducation in PON-1 levels in patient group comparing to control group. The conclusion could be drown from this study that visfatin and PON-1 effected hyperthyroidism patient's with dyslipidemia All the patients in hyperthyroid group were heterozygotes for Familial Hypercholesterolemia is a disorder that is passed down through families. It causes LDL (bad) cholesterol level to be very high. The condition begins at birth and can cause heart attacks at an early age.

Lipidomic differentiation of Graves' ophthalmopathy in plasma and urine from Graves' disease patients

Approximately 50% of patients with Graves' disease (GD) develop retracted eyelids with bulging eyes, known as Graves' ophthalmopathy (GO). However, no simple diagnostic blood marker for distinguishing GO from GD has been developed yet. The objective of this study was to conduct comprehensive profiling of lipids using plasma and urine samples from patients with GD and GO undergoing antithyroid therapy using nanoflow ultrahigh performance liquid chromatography electrospray ionization tandem mass spectrometry. Plasma (n = 86) and urine (n = 75) samples were collected from 23 patients with GD without GO, 31 patients with GO, and 32 healthy controls. Among 389 plasma and 273 urinary lipids that were structurally identified, 281 plasma and 191 urinary lipids were quantified in selected reaction monitoring mode. High-abundance lipids were significantly altered, indicating that the development of GD is evidently related to altered lipid metabolism in both plasma and urine. Several urinary lysophosphatidylcholine species were found to be increased (3- to 10-fold) in both GD and GO. While the overall lipid profiles between GD and GO were similar, significant changes (area under receiver operating curve > 0.8) in GO vs. GD were observed in a few lipid profiles: 58:7-TG and (16:1,18:0)-DG from plasma, 16:1-PC and 50:1-TG from urine, and d18:1-S1P from both plasma and urine samples. An altered metabolism of lipids associated with the additional development of ophthalmopathy was confirmed with the discovery of several candidate markers. These can be suggested as candidate markers for differentiating the state of GO and GD patients based on plasma or urinary lipidomic analysis. Graphical abstract.

Dyslipidemia in subclinical hypothyroidism requires assessment of small dense low density lipoprotein cholesterol (sdLDL-C)

BACKGROUND

Usually both hypothyroidism and hyperthyroidism are related to the cardiovascular and cerebrovascular disease development. The relationship between subclinical hypothyroidism has been widely investigated but the findings remain controversial. The aim of the present study was to evaluate the lipid profile in patients with subclinical hypothyroidism (SHypo) in comparison to controls and to determine the association of SHypo and dyslipidemia in attempt to find importance of small dense low-density lipoprotein cholesterol (sdLDL-C) in atherosclerosis.

MATERIAL AND METHODS

In this study we included 100 women, aged 30 to 70 years that were divided into subgroups according to their age. According to the values of levels of thyroid hormones they were divided into euthyroid (control) group (n = 64) and (newly discovered) subclinical hypothyroidism (SHypo) group (n = 36). A high-sensitivity C-reactive protein (hs-CRP) and lipid profile, including small dense low-density lipoprotein cholesterol (sdLDL-C) were determined. Body weight and height were measured and BMI calculated. History of the current illness, medication, alcohol consumption and cigarettes smoking were noted.

RESULTS

Changed lipid profile as well as elevated triglycerides and sdLDL-C were observed in the group with subclinical hypothyroidism compared to the control group.

CONCLUSIONS

It is important to determine serum lipid levels, especially serum sdLDL-C levels at an early stage of subclinical hypothyroidism, since they represent atherogenic LDL particles and are better indicators for dyslipidaemia in subclinical hypothyroidism and the development of atherosclerosis with potential complications such as cardiovascular and cerebrovascular diseases.

High atherogenic index of plasma in subclinical hypothyroidism: Implications in assessment of cardiovascular disease risk

BACKGROUND

A controversy exists regarding the association between subclinical hypothyroidism (SH) and dyslipidemia. Moreover, studies on lipid ratios and atherogenic index of plasma (AIP) in SH are rare, particularly in the Indian scenario.

AIM

This study aimed to investigate abnormalities in conventional lipid profile, lipid ratios, and AIP in SH and attempted to correlate thyroid stimulating hormone (TSH) and AIP in SH.

MATERIALS AND METHODS

In this retrospective analysis of patient records of SH subjects and euthyroid subjects, age, free triiodothyronine, free thyroxine, TSH, total cholesterol, triglycerides, high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol, lipid ratios, and AIP were compared between the two groups. The correlation of TSH and AIP in SH was studied. Spearman's correlation, Mann-Whitney U-test and logistic regression analysis were performed.

RESULTS

Triglyceride, triglyceride/HDL-C, and AIP were significantly higher in SH as compared to euthyroid group, but there was no correlation between TSH and AIP in SH. AIP emerged as the significant single factor associated with SH in multiple logistic regressions.

CONCLUSION

The positive association of dyslipidemia and SH indicates a need for regular screening of these patients to enable early diagnosis and treatment of dyslipidemia. Even in patients who have a normal conventional lipid profile, lipid ratios, and AIP have to be calculated for better assessment of atherogenic risk.

Atherogenic Lipoproteins in Subclinical Hypothyroidism and Their Relationship with Hepatic Lipase Activity: Response to Replacement Treatment with Levothyroxine

BACKGROUND

Qualitative lipoprotein changes, such as an increase in fasting remnants, are reported in subclinical hypothyroidism (SCH). It was hypothesized that such changes are due to reduced hepatic lipase (HL) activity in SCH: HL is an enzyme regulated by thyroid hormones, and is involved in the degradation of triglyceride (TG)-rich remnants. This study aimed to quantify remnant-like lipoproteins (RLP), small dense LDL (sdLDL), and HL activity in women with SCH, and to assess these parameters after levothyroxine replacement therapy.

METHODS

This was an observational cross-sectional study with a subsequent longitudinal follow-up. Findings in women with thyrotropin levels >4.5 mIU/L (SH group) were compared with age- and body mass index (BMI)-matched euthyroid women (control group). In addition, a subgroup analysis was undertaken in SCH women who chose to receive levothyroxine treatment (0.9 μg/kg/day) for 6 months. RLP was quantified by measuring cholesterol (RLP-C) and triglycerides (RLP-TG) after immunoaffinity chromatography, and sdLDL by automated standardized methods; HL activity was measured in post-heparin plasma.

RESULTS

The SCH group included 37 women; 29 women were included in the control group. In addition, 22 women with SCH were included in the subgroup analysis (levothyroxine treatment). Significantly higher RLP values were observed in the SCH group than in the control group: RLP-C (median [range], mg/dL): 20.3 (5.8-66.8) versus 10.2 (2.7-36.3), p = 0.005; RLP-TG (mg/dL): 26.3 (3.2-123.3) versus 12.1 (2.5-61.6), p = 0.033. HL activity (mean ± standard deviation [SD], μmol free fatty acid/mL post-heparin plasma.h)-9.83 ± 4.25 versus 9.92 ± 5.20, p = 0.707-and sdLDL levels (mg/dL)-23.1 ± 10.7 versus 22.6 ± 8.4, p = 0.83-were similar. After levothyroxine, RLP-C decreased-21.5 (5.8-66.8) versus 17.2 (4.1-45.6), p = 0.023-and HL increased-9.75 ± 4.04 versus 11.86 ± 4.58, p = 0.012-in the subgroup of SCH women. No changes in sdLDL were observed.

CONCLUSIONS

Women with SCH have higher RLP levels than matched controls do, but their RLP-C levels decrease significantly following levothyroxine therapy. Furthermore, HL activity also increases after levothyroxine therapy and can be interpreted as a possible explanation for the decrease in RLP-C.

Lower-normal TSH is associated with better metabolic risk factors: A cross-sectional study on Spanish men

BACKGROUND AND AIMS

Subclinical thyroid conditions, defined by normal thyroxin (T4) but abnormal thyroid-stimulating hormone (TSH) levels, may be associated with cardiovascular and metabolic risk. More recently, TSH levels within the normal range have been suggested to be associated with metabolic syndrome and cardiovascular risk. This work studies the linearity of the relationship between metabolic syndrome and TSH across the euthyroid range.

METHODS AND RESULTS

We studied 3533 male participants of the Aragon Workers' Health Study (AWHS) with normal TSH and free T4 levels, across quintiles of these variables, after adjusting for age, alcohol intake, and smoking. Compared with the lowest TSH quintile, the odds ratios for metabolic syndrome at the higher quintiles, which indicate lower thyroid function, were 1.34 (1.04, 1.73), 1.56 (1.21, 2.01), 1.57 (1.22, 2.03), and 1.71 (1.32, 2.21). The lowest free T4 quintile also showed an odds ratio of 1.49 (1.16, 1.90) with respect to the highest quintile. In addition, spline models showed departures from linearity: the risk of metabolic syndrome mostly increases at TSH values below the median (sample half-closest to subclinical hyperthyroidism). Interestingly, glucose also increases with TSH primarily below the median TSH, diastolic blood pressure shows similar changes across the entire TSH range, whereas body mass index, triglycerides, and high-density lipoprotein (HDL)-cholesterol change only at the highest normal TSH values, which are associated with lower free T4 concentration.

CONCLUSIONS

TSH and free T4 within the normal range are associated with the metabolic syndrome. The sample half-below the TSH median (with probably higher functional thyroid status) exhibited better metabolic and cardiovascular profiles.

The effects of treatment on lipoprotein subfractions evaluated by polyacrylamide gel electrophoresis in patients with autoimmune hypothyroidism and hyperthyroidism

BACKGROUND

Atherogenic dyslipoproteinemia is one of the most important risk factor for atherosclerotic changes development. Hypothyroidism is one of the most common causes of secondary dyslipidemias which results from reduced LDL clearance and therefore raised levels of LDL and apoB. Association between small dense LDL (sdLDL) presentation and thyroid status has been examinated using polyacrylamide gel electrophoresis for lipoprotein subfractions evaluation.

METHODS

40 patients with diagnosed autoimmune hypothyroidism and 30 patients with autoimmune hyperthyroidism were treated with thyroxine replacement or thyreo-suppressive treatment. In both groups lipid profiles, LDL subractions, apolipoproteins (apoA1, apoB), apoA1/apoB ratio and atherogenic index of plazma (AIP) were examined before treatment and in state of euthyreosis.

RESULTS

Thyroxine replacement therapy significantly reduced levels of total cholesterol (TC), LDL, triglycerides (TG) and also decreased levels of sdLDL (8,55±11,671 vs 0,83±1,693mg/dl; p<0,001), apoB and AIP. For estimation of atherogenic lipoprotein profile existence an AIP evaluation seems to be better than apoB measurement because of the more evident relationship with sdLDL (r=0,538; p<0,01). Thyreo-suppressive therapy significantly increased levels of TC, LDL, TG and apoB. The sdLDL was not found in hyperthyroid patients.

CONCLUSIONS

Atherogenic lipoprotein profile was present in 52.5% of hypothyroid subjects, which is higher prevalence than in normal, age-related population. Substitution treatment leads to an improvement of the lipid levels, TG, apoB, AIP and LDL subclasses. It significantly changed the presentation of sdLDL - we noticed shift to large, less atherogenic LDL particles. Significantly positive correlation between sdLDL and TAG; sdLDL and VLDL alerts to hypertriglyceridemia as a major cardiovascular risk factor.

Relation between lipoprotein subfractions and TSH levels in the cardiovascular risk among women with subclinical hypothyroidism

OBJECTIVE

Subclinical hypothyroidism (SCH) is a common condition associated with increased cardiovascular risk. A standard treatment is yet to be established, as there is no consensus on the TSH cut-off values which should be used as indicators. Thus, the aim of this study was to assess cardiovascular risk in patients with SCH and to differentiate it according to TSH levels.

DESIGN

This was an observational study conducted in an academic medical centre.

PATIENTS

The study population consisted of 95 middle-aged women recently diagnosed with SCH and 65 euthyroid controls.

MEASUREMENTS

We measured anthropometric parameters, lipid cardiovascular risk markers and lipoprotein subclasses of HDL and LDL.

RESULTS

Patients with SCH exhibited a significant increase in triglycerides and atherogenic index of plasma and a significant reduction in HDL-cholesterol with respect to the control group after adjusted by age and BMI. A similar lipid profile was observed in both SCH groups. However, patients with TSH levels higher than 10 mIU/l showed a significant reduction in LDL particle size, which was associated with a higher prevalence of atherogenic pattern B.

CONCLUSIONS

Our findings indicate that cardiovascular risk is affected in patients with TSH levels over 10 mIU/l, who have a lipid profile characteristic of atherogenic dyslipidemia.

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.

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.

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.

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.

Lipoprint adequately estimates LDL size distribution, but not absolute size, versus polyacrylamide gradient gel electrophoresis

Recently, a new cost-effective and less labor-intensive technique termed the "lipoprint LDL system" was developed to measure LDL particle size. However, the agreement between lipoprint and previously validated techniques, such as polyacrylamide gradient gel electrophoresis (PGGE), has never been tested. Therefore, we measured LDL size by lipoprint and PGGE in 16 obese subjects at 4 different time points. Lipoprint significantly overestimated (P = 0.003) integrated LDL particle size by 1.1 ± 3.0 Å when compared to PGGE. As for distribution, there was good agreement between methods for the estimation of large, medium, and small particles (mean difference between the methods was <3% for each parameter). Correlational analysis also revealed good relationships between methods for the proportion of large (r = 0.81, P < 0.0001), medium (r = 0.67, P < 0.0001), and small (r = 0.73, P < 0.0001) particles. In sum, although there is good agreement between lipoprint and PGGE for the determination of LDL size distribution, absolute LDL size values may differ between the two methods.

Effects of thyroid dysfunction on lipid profile

Thyroid dysfunction has a great impact on lipids as well as a number of other cardiovascular risk factors. Hypothyroidism is relatively common and is associated with an unfavorable effect on lipids. Substitution therapy is beneficial for patients with overt hypothyroidism, improving lipid profile. However, whether subclinical hypothyroidism should be treated or not is a matter of debate. On the other hand, hyperthyroidism can be associated with acquired hypocholesterolemia or unexplained improvement of lipid profile. Overall, thyroid dysfunction should be taken into account when evaluating and treating dyslipidemic patients.

Carbohydrate response element binding protein gene expression is positively regulated by thyroid hormone

The molecular mechanism of thyroid hormone (TH) effects to fatty acid metabolism in liver is yet to be clear. The carbohydrate response element-binding protein (ChREBP) as well as sterol response element-binding protein (SREBP)-1c plays a pivotal role in hepatic lipogenesis. Both SREBP-1c and ChREBP are target genes of liver X receptors (LXRs). Because LXRs and TH receptors (TRs) cross talk mutually in many aspects of transcription, we examined whether TRs regulate the mouse ChREBP gene expression. In the current study, we demonstrated that TH up-regulated mouse ChREBP mRNA and protein expression in liver. Run-on and luciferase assays showed that TH and TR-beta1 positively regulated the ChREBP gene transcription. The mouse ChREBP gene promoter contains two direct repeat-4 sites (LXRE1 and LXRE2) and EMSAs demonstrated that LXR-alpha and TR-beta1 prefer to bind LXRE1 and LXRE2, respectively. The direct repeat-4 deletion and LXRE2 mutants of the promoter deteriorate the positive regulation by TR-beta1, indicating that LXRE2 is functionally important for the regulation. We also showed that human ChREBP gene expression and promoter activities were up-regulated by TH. These data suggest that ChREBP mRNA expression is positively regulated by TR-beta1 and TH at the transcriptional level in mammals. This novel observation indicates that TH fine-tunes hepatic lipogenesis via regulating SREBP-1c and ChREBP gene expression reciprocally.

Relationship of low-density lipoprotein (LDL) particle size to thyroid function status in Koreans

OBJECTIVE

Dyslipidaemia is a well-known manifestation of thyroid dysfunction. Recently, small low-density lipoprotein (LDL) particle size has been linked with development of cardiovascular disease. To better understand the effects of thyroid dysfunction on the development of cardiovascular disease, we examined LDL particle size and lipid profiles in subjects with different thyroid function.

METHODS

Included were 46 patients with overt hypothyroidism, 57 patients with subclinical hypothyroidism, 46 patients with overt hyperthyroidism, 51 patients with subclinical hyperthyroidism, and 110 age- and sex-matched healthy control subjects. We measured LDL particle size and lipid profiles in these subjects.

RESULTS

No significant differences were found in LDL particle size between the groups with different thyroid function. Serum total cholesterol and LDL-cholesterol levels were significantly higher in the cases of hypothyroidism than in the cases of hyperthyroidism and the healthy control subjects. Serum triglyceride levels were higher in subjects with overt hypothyroidism than in those with overt hyperthyroidism or healthy control subjects.

CONCLUSIONS

LDL particle size, the emerging risk factor for atherosclerosis, did not appear to be significantly affected by the degree of thyroid dysfunction. Increased risk of atherosclerosis in hypothyroidism does not appear to be associated with LDL particle size, the non-traditional cardiovascular risk factor.