Dyslipidemia In Hypothyroidism Research Articles

Update on dyslipidemia in hypothyroidism: the mechanism of dyslipidemia in hypothyroidism

Hypothyroidism is often associated with elevated serum levels of total cholesterol, LDL-C and triglycerides. Thyroid hormone (TH) affects the production, clearance and transformation of cholesterol, but current research shows that thyroid-stimulating hormone (TSH) also participates in lipid metabolism independently of TH. Therefore, the mechanism of hypothyroidism-related dyslipidemia is associated with the decrease of TH and the increase of TSH levels. Some newly identified regulatory factors, such as proprotein convertase subtilisin/kexin type 9, angiogenin-like proteins and fibroblast growth factors are the underlying causes of dyslipidemia in hypothyroidism. HDL serum concentration changes were not consistent, and its function was reportedly impaired. The current review focuses on the updated understanding of the mechanism of hypothyroidism-related dyslipidemia.

The Prevalence of Metabolic Syndrome among Adult Filipinos with Hypothyroidism: A Retrospective Cohort Study

Background and Objectives. Dyslipidemia in hypothyroidism results from the effects of thyroid hormones on lipid metabolism. These, in combination with hypothyroidism-induced hemodynamic changes, are risk factors for cardiometabolic diseases. We determined the prevalence of metabolic syndrome (MS) among adult Filipinos with hypothyroidism and compared clinical and laboratory characteristics of those with versus without MS. Methods. This is a retrospective study of 105 patients with biochemically confirmed hypothyroidism. A review of records obtained anthropometric measurements, blood pressure, fasting blood glucose, lipid profile, and thyroid hormones. Clinical and laboratory characteristics were then compared between MS and those without. Significant differences were determined by two-way ANOVA, while heterogeneity of categorical variables was determined by chi-square or Fisher exact test. All data analyses were performed using Stata version 17.0 with a significance level of p<0.05. Results. The prevalence of MS is 36.19% (95%CI: 27.04%,46.15%). Body mass index (BMI) peaks at obese class I among those with MS. There is a significantly higher proportion of patients diagnosed to have diabetes (28.95% vs. 7.46%; p=0.003) and hypertension (52.63% vs. 14.93%; p<0.001) in the MS group. No significant differences were noted between groups regarding age, sex, etiology of hypothyroidism, blood pressure, fasting glucose, lipid profile, and thyroid hormone levels. Conclusion. Our study showed that the prevalence of MS in adult Filipinos with hypothyroidism is increased at 36.19%. Only BMI, presence of diabetes, and hypertension were shown to be significantly higher. Emphasis must be placed on early screening among hypothyroid patients at high risk of developing MS. A prospective study using waist circumference and clinical and metabolic parameters is needed to validate these findings.

Total cholesterol/high density lipoprotein-cholesterol ratio as an indicator of Dyslipidemia in hypothyroidism

Background: The thyroid hormones are involved in controlling metabolism, growth and functions of various organ systems of our body. Hypothyroidism, a very common endocrinopathy features reduced production of thyroid hormones. In hypothyroidism we encounter abnormal circulating lipid fractions which is termed as ‘Dyslipidemia’. The coexistence of dyslipidemia and hypothyroidism is associated with development of atherosclerosis. Aim: This research is undertaken to assess the potential of TC/HDL-C ratio to disclose dyslipidemia in hypothyroidism. Methodology: The study consists of two major groups, the ‘Cases’ comprising of Fifty hypothyroid patients and ‘Controls’, with fifty age and gender matched healthy adults. The Cases are further subdivided into Twenty ‘Known cases’ of Hypothyroid patients, already receiving treatment and thirty ‘New cases’. The ‘New cases’ sub group further is subdivided as Twenty-one ‘Overt hypothyroids’(OH) and nine ‘Subclinical Hypothyroids’ (SCH). The Biochemical parameters estimated in all subjects of the study includes, Serum TSH, T3, T4, Total Cholesterol (TC) and High density lipoprotein-cholesterol(HDL-C). TC/HDL ratio was then calculated . Result: The study shows a significant elevation (p = 0.05) in the TC/HDL-C ratio in hypothyroid patients (3.67 ± 1.02) when compared to healthy controls (3.29 ± 0.95). TC/HDL-C ratio is more elevated in OH (4.01 ± 1.28) than in SCH (3.46 ± 0.92). The levels in ‘New cases’ sub-group and OH sub sub group have significantly higher ratio than in healthy controls (p = 0.02 and p = 0.01 respectively). TC/HDL-C ratio value in “known cases’ group who are those hypothyroid patients on Levo-thyroxine therapy is (3.40 ± 0.61) less than those who are newly diagnosed. Conclusion: TC/HDL-C ratio is not only raised in hypothyroid patients but it is seen increasing with severity and prolonged duration of disease. The calculation of TC/HDL-C ratio should be routinely put into practice to detect hypothyroid patients with dyslipidemia.

Non High Density Lipoprotein Cholesterol, a Simple and Reliable Marker to Assess Cardiovascular Disease Risk in Hypothyroid Patients

Introduction: Thyroid hormones regulate growth, metabolism and cellular differentiation in our body. Thyroid disorders are among the commonly encountered endocrinopathies across the globe in the recent past. Hypothyroidism is prevalent to the extent of 9.45-11.73% among urban inland regions of India as reported in a recent survey. Thyroid hormones influence lipid metabolism. The dyslipidemia in hypothyroidism presents as high serum Total Cholesterol (TC) levels, elevated Low Density Lipoprotein-Cholesterol (LDL-C) levels, hypertriglyceridemia and Increased Triglyceride (TGL)- Rich Lipoproteins or Remnant Lipoproteins (RLPs). Non High Density Lipoprotein-Cholesterol (Non-HDL-C) reflects the cholesterol content of these RLPs. The potential of Non-HDL-C seems to be underutilised in patients with hypothyroidism. Aim: To know the levels of Non-HDL-C in hypothyroid patients as compared to normal subjects and to assess its reliability to predict the future cardiovascular risk in hypothyroid patients. Materials and Methods: The study was a case-control study, that was conducted in District Hospital, Chamarajanagar, Karnataka, India, between December 2019 to September 2020, involving two groups. The first group were the cases, consisting of 50 hypothyroid patients between 18 and 55 years of age, 50 healthy age and sex matched controls were selected and inducted into this study. The ‘Case group was further divided into “Known cases” and ‘New cases’, based on the disease course. The ‘New cases’ are further classified into group of ‘Overt Hypothyroids’ and ‘Subclinical hypothyroids’. In all the subjects of present study, serum TC and serum HDL- Cholesterol (HDL-C) was estimated. The value of HDL-C was subtracted from TC level and Non-HDL-C level was calculated for all the study subjects. The values of the lipid fractions in both groups and in the subgroup were tabulated and compared using suitable statistical tool. Results: In the present study it was noted that Non-HDL-C was significantly high in hypothyroid patients when compared to healthy controls (p=0.02). Also, the newly diagnosed hypothyroid patients had significantly high Non-HDL-C levels than controls (p=0.01). The subgroup of ‘Known cases’ who were on Levo- thyroxine replacement did not show significantly elevated Non- HDL-C levels. Overt Hypothyroid (OH) patients had higher values of Non-HDL-C than those with Subclinical Hypothyroidism (SCH). Conclusion: At each level of the present study, (controls vs cases, known vs new cases and OH vs SCH) non-HDL-C has emerged in an expected pattern, which is consistent with pathophysiology, course and severity of the disease. Therefore, present study suggest the feasibilty of non-HDL-C replacing the traditional lipid profile assays for assessment of dyslipidemia in hypothyroid patients.

Decreased Expression of Hepatic Low-Density Lipoprotein Receptor–Related Protein 1 in Hypothyroidism: A Novel Mechanism of Atherogenic Dyslipidemia in Hypothyroidism

The atherogenic effects of hypothyroidism on lipid metabolism could result, in part, from the reduced clearance of remnant lipoproteins. In this study, we investigated the expression of hepatic low-density lipoprotein receptor-related protein 1 (LRP1), a receptor for remnant lipoproteins, in hypothyroidism and the effect of 3,3',5-triiodo-L-thyronine (T3) treatment on hepatic LRP1 expression. C57BL/6 mice were fed a normal diet (control group) or a low-iodine diet supplemented with 0.15% propylthiouracil (PTU/LI group) for 4 weeks. Mice in the PTU/LI group were injected intraperitoneally with T3 (0, 30, and 150 μg/kg of body weight) for 7 days. HepG2 cells were incubated in fetal bovine serum or charcoal-stripped fetal bovine serum with various concentrations of T3. The expression and function of LRP1 in liver samples and cells were analyzed. Hypothyroidism was successfully induced in PTU/LI mice. Hepatic LRP1 protein expression was lower in the PTU/LI group than in the control group. T3 treatment upregulated hepatic LRP1 protein expression in PTU/LI mice. LRP1 expression in HepG2 cells was reduced after incubation in the medium containing charcoal-stripped fetal bovine serum, which mimics hypothyroidism in vitro, and was recovered by T3 treatment. The protein expression of LRP1 in HepG2 cells was increased by T3 treatment in a dose-dependent manner up to 2.0 nM T3. However, LRP1 mRNA transcription was not affected by hypothyroidism conditions or T3 treatment, either in liver samples or in HepG2 cells. T3 treatment on HepG2 cells increased cellular uptake of lipid-conjugated apolipoprotein E through LRP1. Our data demonstrate that hepatic LRP1 expression and function decrease in hypothyroidism and are regulated by the thyroid hormone. These results suggest that in hypothyroidism, decreased expression of hepatic LRP1 may be associated with reduced clearance of circulating remnant lipoproteins.