LDL in patients with subclinical hypothyroidism shows increased lipid peroxidation

The Relationship between Subclinical Hypothyroidism and Carotid Intima-Media Thickness as a Potential Marker of Cardiovascular Risk: A Systematic Review and a Meta-Analysis

BACKGROUND AND OBJECTIVES

Thyroid dysfunction is known to have significant consequences on the cardiovascular system. The correlation between carotid intima-media thickness (CIMT) and subclinical hypothyroidism (SCH) has been frequently evaluated in clinical studies in recent years. This study aimed to evaluate the significance of this association through a meta-analysis.

METHODS

We conducted a systematic search of PubMed, MedLine, Scopus, and Web of Science databases using the keywords 'subclinical hypothyroidism and carotid intima-media thickness', from the beginning of each database until January 2023. We established the inclusion and exclusion criteria and considered studies that met the inclusion criteria. We used Jamovi for statistical analysis of the data.

RESULTS

We identified 39 observational studies that met the inclusion criteria, with 3430 subjects: 1545 SCH and 1885 EU. Compared to euthyroid subjects (EU), subjects with subclinical hypothyroidism (SCH) had significantly increased carotid intima-media thickness (CIMT) values; the estimated average mean difference was 0.08 (95% CI 0.05 to 0.10), p < 0.01, I2 = 93.82%. After the sensitivity analysis, a total of 19 from the 39 abovementioned studies were analyzed, with most studies showing a positive association between SCH and thickening of the carotid wall; the estimated average mean difference was 0.04 (95% CI 0.02 to 0.07), p = 0.03, I2 = 77.7. In addition, female sex, advanced age, and high cholesterol levels statistically significantly influenced this association.

CONCLUSIONS

Our meta-analysis indicates a significant positive association between SCH and increased CIMT, but with some limitations.

The relationship between thyroid hormones and lipid profile in subclinical hypothyroidism female patients

Background and objectives: Subclinical thyroid disorder is a most common subclinical disease among many medical conditions such as cardiovascular disease and subclinical Lyme disease. The aim of this study was to determine the relationship between lipid profile results, lipid ratios, and anthropometric parameters and thyroid hormones. Methods: One hundred patients (ages 20 to 50 years) with subclinical hypothyroidism (SHT group) and 50 healthy subjects (control group), who are age-matched with patients, were included in the current study. Thyroid function tests (TSH, T3 and T4) were determined by immunodiagnostic assay system (VIDAS) for all participants. The serum glucose and lipid profile tests parameters were evaluated by Biolis 24i Premium chemistry analyser. In addition, systolic and diastolic blood pressure were measured for each individual in the study using mercury sphygmomanometer. Results: The levels of high-density lipoprotein-cholesterol (HDL-c) were significantly lower in the SHT group when compared with control group. Whereas, the level of low-density lipoprotein-cholesterol (LDL-c), the ratios total cholesterol (TC)/HDL-c and LDL-c/HDL-c were significantly higher in SHT group than in controls. Moreover, TSH was negatively correlated with diastolic blood pressure. Conclusions: Both LDL-c and HDL-c are altered in subclinical hypothyroidism patients. And, there is a negative association between TSH and diastolic blood pressure.

SERUM LEVELS OF OXIDATIVE STRESS MARKERS IN SUBCLINICAL AND OVERT HYPOTHYROIDISM VERSUS CONTROL GROUP IN POPULATION OF KUTAHYA CITY, TURKEY

Background: Overproduction of oxygen-related free radicals and inadequate antioxidant defense are critical in hypothyroidism, as they might lead to future life-threatening diseases. The objectives of this study were to compare serum levels of oxidative stress markers; total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), paraoxonase-1 (PON-1), and arylesterase (ARYL) in patients with subclinical hypothyroidism (SH) and overt hypothyroidism (OH) versus healthy controls in population of Kutahya city, Turkey.Materials Methods: This cross-sectional study was conducted at Department of Biochemistry, Faculty of Medicine, Kutahya University of Health Sciences, Kutahya, Turkey, from July to December, 2016. Three study groups of 45 each were formed as healthy controls, patients with SH and OH. Serum levels of TOS, TAS, OSI, PON-1, and ARYL were five research variables with ratio scale, but skewed, so described by median and IQR with 95% Cl. Kruskal-Wallis and multiple comparison tests were used for hypotheses testing.Results: Serum levels of TOS and OSI were higher in SH group (p-values 0.032; .0001; respectively) and OH group (p-values .0001; .0001, respectively) than healthy controls, while serum levels of TAS, PON-1 and ARYL were lower in SH group (p-values .0001; .0001; .0001, respectively) and OH group (p-values .0001; .0001; .0001, respectively) than control group.Conclusion: Our study showed that serum levels of TOS and OSI were higher in subclinical and overt hypothyroidism than in healthy controls; while serum levels of TAS, PON-1, and ARYL were lower in subclinical and overt hypothyroidism than in healthy controls.

Correlation Between Serum TSH Levels Within Normal Range and Serum Lipid Profile

The aim of the work was to investigate the correlation between serum TSH (thyrotropin) levels within normal range and serum lipids. A total of 1962 subjects with normal thyroid function were enrolled. The subjects were divided into four groups according to the quartiles of serum normal TSH levels, [Q₁ (0.27-1.68) mIU/l, Q₂ (1.69-2.35) mIU/l, Q₃ (2.36-3.07) mIU/l, and Q₄ (3.08-4.20) mIU/l]. The effect of serum normal TSH levels on serum lipid profiles of different age or gender was analyzed. The total cholesterol (TC), triglyceride (TG), and low-density lipoprotein cholesterol (LDL-C) levels of the Q₃ group and TG levels of the Q₄ group were higher than those of the Q₁ group in youth (p <0.05). The TC levels of the Q₃ group were higher than those of the Q₂ group in middle age (p <0.05). The LDL-C levels of middle age or elderly were higher than those of youth at the same TSH levels (p <0.05), while the TC levels of middle age were higher than those of youth in Q₁, Q₃, or Q₄ group (p <0.05), and the TC and HDL-C levels of elderly were higher than those of youth in the Q₂ group (p <0.05). The TG levels of the Q₃ group were higher than those of Q₁ group in males (p <0.05). The LDL-C levels of the Q₃ group were higher than those of the Q₁ group in females (p <0.05). In conclusion, the normal serum TSH levels were found to be closely related to serum lipid profiles, and with increasing TSH levels, serum lipids levels increased gradually.

Electroacupuncture Inhibits Atherosclerosis through Regulating Intestinal Flora and Host Metabolites in Rabbit

Methods

In this study, general rabbit conditions, vascular histology, metabolites, and intestinal flora structures were analyzed. Integrated analysis of metabolomics and 16S rRNA sequencing were performed. All the rabbits were randomly divided into four groups. The rabbit model of atherosclerosis was established. The histopathological change in the common carotid artery was assessed by HE staining and the structural change in the flora by 16S rRNA sequencing. HPLC-TOF-MS and Agilent MPP 12.1 were integrated to identify and screen out differential metabolites. Correlational analyses of every differential metabolite with intestinal flora were integrated on Omicshare platform.

Results

Atherosclerotic rabbits showed obvious changes in general conditions, significant fibrous cap and necrotic center on carotid artery, abnormal intestinal bacteria structure, and metabolites levels. Electroacupuncture improved the conditions, reduced lipid deposition on the carotid artery wall, diversified intestinal flora, and normalized host metabolism. Integrated analysis showed that 149 altered metabolites were related to 22 intestinal flora, among which eight intestinal floras and 21 metabolites have relationships with atherosclerosis.

Conclusion

Electroacupuncture can effectively reverse atherosclerosis through manipulating the structural feature of intestinal flora to influence the host metabolites. The possible mechanisms involved activating signal pathways through host metabolites or affecting the activity of cardiovascular-related enzymes, or regulating host lipid metabolism directly.

Evaluation of biochemical markers of kidney function in patients with subclinical hypothyroidism in comparison with euthyroid people

Background:

Subclinical hypothyroidism (SCH) as a compensated or preclinical type of primary and overt hypothyroidism (OHT) can affect approximately 4–10% of the general population. Treating SCH can slowdown the progression to OHT, the formation of cardiovascular diseases, neuropsychiatric symptoms, and other miscellaneous problems.

Materials and Methods:

The present study is a case-control study that was conducted on 239 adults who were referred to 501 Imam Reza Hospital from March 2019 up to September 2019. Of the 239 patients and their families admitted to the hospital, 121 (50.6%) were euthyroid (as control group) and the remaining participants (118, 49.4%) were SCH (as case group). The serum levels of thyroid stimulating hormone (TSH), urea, uric acid, creatinine, T3, and T4 were asked to be determined at a single laboratory. Biochemical markers of kidney function and the level of thyroid hormones were compared between the two groups of euthyroid and SCH.

Results:

TSH was significantly higher in SCH (7.25 (4.4-18.15)) compared to euthyroid (1.4 (0.2-3.7)) patients (P < 0.001). Among biochemical markers, creatinine (P < 0.001) and uric acid (P = 0.006) had higher serum levels in the case group. There was no remarkable difference in the thyroxine hormone levels and urea between the euthyroid and SCH patients (P > 0.05). Within the SCH group, there was a significant positive correlation between TSH and the level of creatinine (P = 0.001, r = 0.302).

Conclusion:

Regular monitoring of the major function of the kidneys in patients with hypothyroidism and SCH can help early diagnosis of kidney dysfunction, thus increasing the chance of restoring normal kidney function.

The current debate over treatment of subclinical hypothyroidism to prevent cardiovascular complications

BACKGROUND

Subclinical hypothyroidism (SCH) is an asymptomatic condition associated with increased thyroid-stimulating hormone (TSH) >4 mIU/L with normal thyroxine (T4) and triidothyronine (T3) levels. It is more common in older subjects and especially in women with an overall incidence of 10%.

OBJECTIVE

Because the normal TSH levels increase with age up to 7.5 mIU/L in older people, several studies have reported either no benefits whereas others have reported the benefits of treatment. These studies have caused a great debate over the treatment of SCH, especially in older subjects. Therefore, the objective of this study was to review the current evidence over this debate by reviewing the recent literature on the subject to discern whether treatment of SCH is necessary and under what circumstances.

METHODS

To get a better perspective on the current debate over treatment of SCH, a focused Medline search of the English language literature was conducted from 2012 to 2019 using the terms, hypothyroidism, subclinical, dyslipidaemia, cardiovascular disease, heart failure and 38 papers with pertinent information were selected.

RESULTS

The analysis of results from these papers indicated that the normal levels of TSH are increasing with the advancement of age from 4 mIU/L up to 7.5 mIU/L for patients ≥75 years of age. Also, several of reviewed studies have shown no benefits of treatment whereas, others have shown definite benefits of treatment with levothyroxine supplementation on the clinical and metabolic effects of SBH with reductions in CVD, HF and mortality. The treatment is more effective in younger persons and less so in older persons.

CONCLUSIONS

Based on the overall evidence, treatment of SCH is indicated in younger persons with a TSH level >4.0 mIU/L. In older subjects, treatment should be individualised and based on the presence of symptoms, the level of TSH, and initiated at TSH levels ≥10 mIU/L and at low doses to avoid adverse cardiovascular effects from overtreatment.

Associations of α- and γ-tocopherol during early life with lung function in childhood

BACKGROUND

Tocopherol isoforms may regulate child lung growth and spirometric measures.

OBJECTIVE

Our aim was to determine the extent to which plasma α-tocopherol (α-T) or γ-tocopherol (γ-T) isoform levels in early childhood or in utero are associated with childhood lung function.

METHODS

We included 622 participants in the Project Viva cohort who had lung function at a mid-childhood visit (age 6-10 years). Maternal and child tocopherol isoform levels were measured by HPLC at the second trimester and 3 years of age, respectively. Multivariable linear regression models (adjusted for mid-childhood body mass index z scores, maternal education, smoking in pregnancy, and prenatal particulate matter with diameter of <2.5 micrometers (PM_2.5) particulate exposure) stratified by tertiles of child γ-T level were used to assess the association of α-T levels with FEV₁ and forced vital capacity (FVC) percent predicted. Similarly, models stratified by child α-T tertile evaluated associations of γ-T levels with lung function. We performed similar analyses with maternal second trimester tocopherol isoform levels.

RESULTS

The median maternal second trimester α-T level was 63 μM (interquartile range = 47-82). The median early-childhood level was 25 μM (interquartile range = 20-33 μM). In the lowest tertile of early-childhood γ-T, children with a higher α-T level (per 10 μM) had a higher mid-childhood FEV₁ percent predicted (β = 3.09; 95% CI = 0.58-5.59 and a higher FVC percent predicted (β = 2.77; 95% CI = 0.47-5.06). This protective association of α-T was lost at higher γ-T levels. We did not see any consistent associations of second trimester levels of either α-T or γ-T with mid-childhood FEV₁ or FVC.

CONCLUSION

When γ-T levels were in the lowest tertile, a higher early-childhood α-T level was associated with better lung function at mid-childhood. Second trimester maternal plasma α-T concentration was 3-fold higher than in the adult nonpregnant female population.

Preventive effects of Aframomum melegueta extracts on the reproductive complications of propylthiouracil-induced hypothyroidism in male rat

Recent studies have demonstrated that hypothyroidism is associated with infertility. This work was undertaken to evaluate the protective effects of Aframomum melegueta on testicular functions and fertility of hypothyroid male rats. Male rats were orally treated with propylthiouracil (PTU: 10 mg/kg) in combination with plant aqueous or methanol seed extract (20 and 100 mg/kg) for 56 days. Vitamin E and clomiphene citrate served as positive controls. On day 47 of treatment, each male was mated with two adult females for fertilization potential evaluation. At the end of the treatment, genital sex organ weights, sperm characteristics, testicular histology, oxidative status, plasmatic hormones and fertility potential were evaluated. Results indicated that PTU created hypothyroidism characterised by a significant increase in TSH with reduction of T3 and T4. PTU also lowered genital sex organ weights, sperm count, viability and motility, plasmatic levels of luteinising hormone, follicle-stimulating hormone and testosterone, and increased prolactin, cholesterol and testicular oxidative stress. Alteration in sperm morphology, testis and epididymis histology, and fertilization potential was also noticed. Co-administration with A. melegueta extracts successfully reversed PTU-induced infertility without any effect on thyroid hormones. These results provide evidence that A. melegueta has a protective effect on fertility in hypothyroid condition.

Association of metabolic risks with subclinical hypothyroidism: A cross-sectional analysis

Objective:

To compare lipid parameters, HbA1c, uric acid and albumin creatinine ratio (UACR) among subjects having euthyroidism, Sub-Clinical Hypothyroidism (SCH) and overt hypothyroidism.

Methods:

This comparative cross-sectional analysis was carried out from Dec-2015 to Oct-2016 in collaboration between PNS HAFEEZ hospital and department of chemical pathology and endocrinology, Armed Forces Institute of Pathology, Rawalpindi. Biochemical parameters including lipid indices, HbA1c and UACR were compared between euthyroidism (TSH: 0.5 to 4.0 mIU/L, n=163), subclinical hypothyroidism (TSH: 4.0 to 10 mIU/L, n=16) and overt hypothyroidism (TSH:≥ 10.0 mIU/L, n=9).

Results:

LDL-cholesterol, non-HDL-cholesterol and UACR results were as: [(Euthyroid: 2.66 ± 0.73), (SCH: 2.68 ± 0.51) and (Overt hypothyroidism: 3.23 ± 0.59), p-value=0.063], [(Euthyroid: 3.49 ± 0.64), (SCH: 3.35 ± 0.59) and (Overt hypothyroidism: 4.01 ± 0.30), p-value=0.033] and [{Euthyroid: 2.48 (95% CI: 1.63-3.33)}, {SCH: 2.27 (95% CI: 0.37-4.90)} and {Overt hypothyroidism: 14.95 (95% CI: 10.71-19.14){, (p-value< 0.001)] Results for total cholesterol, triglycerides and HDL-cholesterol though increased in overt hypothyroid group were not found to be statistically significant.

Conclusion:

LDL-cholesterol, non-HDL-cholesterol and UACR increased from euthyroid subjects to overt hypothyroidism group. However, these changes were found to be more subtle in the subclinical hypothyroid subjects than cases with overt hypothyroidism.

Replacement therapy with levothyroxine modulates platelet activation in recent-onset post-thyroidectomy subclinical hypothyroidism

BACKGROUND AND AIM

Subclinical hypothyroidism has been linked to increased risk of atherosclerotic disease. Soluble CD40 ligand (sCD40L), mainly derived from activated platelets, and the lipid peroxidation product 8-iso-prostaglandin F_2α (8-iso-PGF_2α) are known to play a relevant pathophysiological role in atherogenesis. In this study, we analyzed the relationship between thyroid hormones and circulating levels of sCD40L and 8-iso-PGF_2α in patient with recent-onset post-thyroidectomy subclinical hypothyroidism under replacement therapy.

METHODS AND RESULTS

Circulating levels of thyroid hormones, sCD40L, and 8-iso-PGF_2α were assessed in 40 recently thyroidectomized patients (33 females, mean age 52.0 ± 11.7 years) at baseline (5-7 day after surgery) and after 2 months under replacement therapy with levothyroxine (LT-4). At baseline, circulating levels of thyroid hormones were indicative of a subclinical hypothyroidism (TSH 7.7 ± 3.9 μU/mL, FT3 1.8 ± 0.6 pg/mL, and FT3 8.9 ± 3.0 pg/mL). Circulating levels of sCD40L and 8-iso-PGF_2α were directly correlated with each other (r = 0.360, p = 0.023) and with TSH levels (r = 0.322, p = 0.043 and r = 0.329 p = 0.038, respectively). After 2 months under the replacement therapy with LT-4 circulating levels of TSH (from 7.7 ± 3.9 to 2.7 ± 2.8 μU/mL, p < 0.0001), sCD40L (from 6.11 ± 2.41 to 2.43 ± 2.00 ng/mL, p < 0.0001) and 8-iso-PGF_2α (from 45.33 ± 6.94 to 40.36 ± 6.20, p < 0.0001) significantly decreased. Changes in circulating levels of sCD40L and 8-iso-PGF_2α were directly correlated with each other (r = 0.349 p = 0.028) and with changes in TSH levels (r = 0.367 p = 0.020 and r = 0.339 p = 0.032, respectively).

CONCLUSION

Our study suggests an influential role of TSH on proatherogenic activation of platelets, probably through enhanced lipid peroxidation. These findings could partially explain the increased susceptibility of patients with subclinical hypothyroidism to develop atherosclerotic disease.

Significant Improvement Selected Mediators of Inflammation in Phenotypes of Women with PCOS after Reduction and Low GI Diet

Many researchers suggest an increased risk of atherosclerosis in women with polycystic ovary syndrome. In the available literature, there are no studies on the mediators of inflammation in women with PCOS, especially after dietary intervention. Eicosanoids (HETE and HODE) were compared between the biochemical phenotypes of women with PCOS (normal and high androgens) and after the 3-month reduction diet. Eicosanoid profiles (9(S)-HODE, 13(S)-HODE, 5(S)-HETE, 12(S)-HETE, 15(S)-HETE, 5(S)-oxoETE, 16(R)-HETE, 16(S)-HETE and 5(S), 6(R)-lipoxin A₄, 5(S), 6(R), 15(R)-lipoxin A₄) were extracted from 0.5 ml of plasma using solid-phase extraction RP-18 SPE columns. The HPLC separations were performed on a 1260 liquid chromatograph. No significant differences were found in the concentration of analysed eicosanoids in phenotypes of women with PCOS. These women, however, have significantly lower concentration of inflammatory mediators than potentially healthy women from the control group. Dietary intervention leads to a significant (p < 0.01) increase in the synthesis of proinflammatory mediators, reaching similar levels as in the control group. The development of inflammatory reaction in both phenotypes of women with PCOS is similar. The pathways for synthesis of proinflammatory mediators in women with PCOS are dormant, but can be stimulated through a reduction diet. Three-month period of lifestyle change may be too short to stimulate the pathways inhibiting inflammatory process.

Effect of Thyroxin Treatment on Carotid Intima-Media Thickness (CIMT) Reduction in Patients with Subclinical Hypothyroidism (SCH): a Meta-Analysis of Clinical Trials

Aim: Research shows that subclinical hypothyroidism (SCH) is related to an increased carotid intima –media thickness (CIMT), a surrogate marker of subclinical cardiovascular disease (CVD). It is controversial whether or not SCH should be treated to reduce CVD morbidity and mortality. This meta-analysis aimed to determine whether SCH is associated with an increase in CIMT as compared to Euthyroidism (EU) and whether thyroxin (T4) treatment in SCH can reverse the change in CIMT.

Methods: Two independent reviewers conducted an extensive database research up to December 2016. A total of 12 clinical trials discussed the effect of Thyroxin on CIMT values at pre- and post-treatment in subjects with SCH.

Results: CIMT was significantly higher among SCH (n = 280) as compared to EU controls (n = 263) at baseline; the pooled weighted mean difference (WMD) of CIMT was 0.44 mm [95% confidence interval (CI) 0.14, 0.74], p = 0.004; I² = 65%. After treatment with thyroxin in subjects with SCH (n = 314), there was a statistically significant decrease in CIMT from pre- to post-treatment; the pooled WMD of CIMT decrease was [WMD −0.32; 95% CI (−0.47, −0.16), p = < 0.0001; I² = 2%], and it was no longer different from EU controls [WMD 0.13 mm; 95% CI (−0.04, 0.30); p = 0.14; I² = 27%]. The total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL) were higher in SCH as compared to EU controls and decreased significantly after treatment with thyroxin.

Conclusion: This meta-analysis shows that thyroxin therapy in subjects with SCH significantly decreases CIMT and improves lipid profile, modifiable CVD risk factors. Thyroid hormone replacement in subjects with SCH may play a role in slowing down or preventing the progression of atherosclerosis.

Cardiac autonomic function and vascular profile in subclinical hypothyroidism: Increased beat-to-beat QT variability

BACKGROUND

Patients with subclinical hypothyroidism (SH) may have higher incidence of coronary heart disease and autonomic dysfunction.

DESIGN OF THE STUDY

Prospective case control study.

AIM AND OBJECTIVES

To evaluate beat-to-beat QT variability and vascular stiffness in patients with SH compared to normal controls.

MATERIALS AND METHODS

We compared linear and nonlinear measures of cardiac repolarization liability using beat-to-beat QT intervals derived from the surface electrocardiogram during supine posture and vascular indices including pulse wave velocity and ankle-brachial index (ABI) during supine posture between female patients with SH and age- and sex-matched normal controls. Spectral analysis was done at very low frequency (LF) (0.003-0.04 Hz), Low frequency (LF) (0.04-0.15 Hz), and high frequency (HF) (0.15-0.4 Hz). The HF represents vagal regulation (parasympathetic) and LF represents both parasympathetic and sympathetic regulation.

RESULTS

We recruited 58 women with a mean age of 31.83 ± 8.9 years and 49 controls with mean age of 32.4 ± 9.9 years (P = NS). QT variability index (QTvi) was higher in cases compared to controls (P = 0.01). The ratio of LF/HF of R-R interval which is an index of sympathovagal tone was significantly more in cases compared to controls (P = 0.02). The difference in the left minus the right ABI was significant between cases and controls (P = 0.03).

CONCLUSIONS

The cases had lower parasympathetic activity as compared to controls, and there was a predominance of sympathetic activity in cases. QTvi may be an important noninvasive tool in this group of patients to study the risk of cardiovascular mortality.