THYROID FUNCTION AND METABOLIC SYNDROME: A CROSS-SECTIONAL STUDY IN OBESE AND OVERWEIGHT PATIENTS

Retrospective Cross-Sectional Study of the Relationship of Thyroid Volume and Function with Anthropometric Measurements, Body Composition Analysis Parameters, and the Diagnosis of Metabolic Syndrome in Euthyroid People Aged 18-65

Background and Objectives: The thyroid is a key endocrine gland for the regulation of metabolic processes. A body composition analysis (BCA) is a valuable complement to the assessment of body mass index, which is derived only from body weight and height. This cross-sectional retrospective study aimed to investigate the relationships between thyroid volume (TV) and thyroid function parameters, anthropometric measurements, BCA parameters, and the presence of metabolic syndrome (MetS) in adults without clinically overt thyroid disease. Material and Methods: This study involved 45 people (females: 57.8%; MetS: 28.9%) hospitalized for planned diagnostics without signs of acute illness or a deterioration of their health and without thyroid disease, who underwent thyroid ultrasound scans, biochemical tests to assess their thyroid function, MetS assessments, anthropometric measurements, and BCAs using the bioelectrical impedance method. Results: The TV was significantly larger in people with MetS compared to people without MetS. The TV was significantly higher and the serum thyrotropin (TSH) concentration was significantly lower in overweight and obese people than in normal and underweight people. The free triiodothyronine (FT3) serum concentration and TV were correlated with waist circumference and some parameters of the BCA, and the FT3 concentration was also correlated with the body mass index, waist-hip ratio, and waist-height ratio. No significant correlations were found between the FT4 and TSH and the results of the anthropometric and BCA measurements. Conclusions: Even in a population of euthyroid patients without clinically overt thyroid disease, there were some significant relationships between the volume and function of the thyroid gland and the results of their anthropometric parameters, BCAs, and the presence of MetS features.

Evaluation of the frequency and patterns of thyroid dysfunction in patients with metabolic syndrome

Background

Metabolic syndrome (MetS) and thyroid dysfunction have a degree of close association, and each of them affects the other. Due to the associated cardiovascular events, MetS has increased morbidity and mortality. The study tried to detect the frequency of thyroid function in patients with MetS. This is a case control study that recruited 100 patients with MetS and 100 healthy control subjects.

Results

Patients with MetS had significantly higher body mass index and waist circumference. Also, frequency of thyroid dysfunction was significantly higher in MetS group (32% vs. 9%; P<0.001). The most frequent form of thyroid dysfunction was subclinical hypothyroidism: 21% of the MetS group and 6% of the control group. Out of the studied patients with MetS, 13 (13%) patients had three criteria, 55 (55%) patients had four criteria, and 32 (32%) patients had five criteria for MetS.

Conclusion

Patients with MetS are vulnerable to develop thyroid dysfunction mainly subclinical hypothyroidism. So, it is recommended to perform regular screening for those patients as regard thyroid dysfunction.

Association of serum free thyroxine and glucose homeostasis: Korea National Health and Nutrition Examination Survey

BACKGROUND/AIMS

Thyroid hormones are involved in wide range of glucose metabolism functions. Overt thyroid dysfunctions are related to altered glucose homeostasis. However, it is not conclusive as to whether subtle changes in thyroid hormones within normal ranges can induce alterations in glucose homeostasis. The aim of this study was to evaluate the association between thyroid hormone and glucose homeostasis parameters in subjects without overt thyroid dysfunction based on nationwide population data.

METHODS

In the Sixth Korea National Health and Nutrition Examination Survey 2015 (n = 7,380), data were collected from subjects with insulin and thyroid function measurements who were older than 19-years-old. After the exclusion of 5,837 subjects, a total of 1,543 patients were included in the analysis. Subjects were categorized into the quartiles of the free thyroxine (FT4). Fasting glucose, insulin, homeostatic model assessment of insulin resistance and hemoglobin A1c (HbA1c) levels were considered to be glucose homeostasis parameters.

RESULTS

Subjects with the highest FT4 quartile showed significantly lower fasting insulin and HbA1c levels. A significant inverse correlation FT4 and HbA1c levels was observed (β = -0.261, p = 0.025). In the logistic regression analysis, the highest quartile of FT4 was demonstrated to lower the risk of HbA1c to a greater degree than the median by approximately 40%, after adjusting for confounders, compared to the lowest quartile (p = 0.028).

CONCLUSION

We demonstrated subjects with a lower FT4 quartile exhibited high risk of HbA1c levels above the median value in a representative Korean population. Subjects with the lowest FT4 quartile should be cautiously managed in terms of altered glucose homeostasis.

Thyroid disease and the metabolic syndrome

PURPOSE OF REVIEW

To summarize recent developments in the association of thyroid function with metabolic syndrome (MetS).

RECENT FINDINGS

Although thyroid hormones even within low normal range are associated with various metabolic abnormalities, the risk of MetS remains a controversial issue. Hyperthyroid state might be associated only with insulin resistance and dysglycemia. Autoimmune thyroid diseases may be a potential risk factor for metabolic abnormalities even in those with low normal thyroid function.

SUMMARY

The interrelation between thyroid stimulating hormone, free T3, freeT4 and metabolic parameters is complex and might be affected by age, sex, BMI, insulin resistance, smoking, iodine intake and inflammatory markers.

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

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

A Mechanism Exploration of Metabolic Syndrome Causing Nodular Thyroid Disease

BACKGROUND

Metabolic syndrome (MS) and its components have been demonstrated to facilitate the prevalence of thyroid nodules (TNs). The underlying pathogenesis needs to be elucidated.

METHODS

A total of 2722 subjects, who underwent health checkup in our institute from December 2014 to November 2018, were retrospectively and randomly collected. After exclusion, 2068 subjects were chosen, and their anthropic and clinical data were collected.

RESULTS

After matching age, gender, uric acid (UA), and creatinine (Cr) by propensity score matching (PSM), subjects with MS had higher prevalence of TNs than those without MS, as well as higher thyroid-stimulating hormone (TSH) and inflammatory levels, indicated by the higher white blood cell (WBC), lymphocyte (LY), and monocyte/high-density lipoprotein (Mo/HDL). After matching age, gender, UA, Cr, TSH, free triiodothyronine (FT3), thyroxine (FT4), WBC, NE, LY, Mo, NE/LY, LY/Mo, and Mo/HDL by PSM, no significant difference of the prevalence of TNs was found between MS and non-MS groups. Step logistic regression suggested glucose intolerance (GI), among all the components of MS, was an independent impact factor of TNs and was considered to contribute most to the formation of TNs. The prevalence of TNs was higher in the GI group after matching age, gender, body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting blood sugar (FBS), UA, Cr, triglyceride (TG), cholesterol (CHOL), HDL, and low-density lipoprotein (LDL).

CONCLUSIONS

Patients with MS have a higher prevalence of TNs, probably due to the elevated TSH and inflammatory levels in vivo. Among the components of MS, glucose intolerance contributes most to the development of TNs.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Association of divalent cations and insulin resistance with thyroid hormones in patients with type 2 diabetes mellitus

AIM

The study was primarily aimed at investigating the association of Magnesium and Zinc levels in the serum of adult Non- obese and Obese type 2 diabetic patients, with particular reference to thyroid comorbidity.

METHODS

108 patients with T2DM of both genders (24 Non obese and 84 Obese) were enrolled from a tertiary health care unit in Puducherry. The cardio-metabolic risk factors were assessed through body mass index, Waist hip ratio, blood pressure, fasting blood glucose, lipid profile and glycated haemoglobin. Zinc and Magnesium were quantitated. Insulin resistance was by Homeostasis model assessment. Serum free T4, T3 and TSH were also measured.

RESULTS

In non-obese type 2 diabetic group, Glycated haemoglobin had a strong positive correlation with free T4(r=0.784; p=0.003).TSH also depicted a positive association with HOMA-IR (r=0.924; p<0.001); whereas,T3 and Insulin had negative correlation with Magnesium (r=-0.599* and r=-0.620*; p 0.04 and 0.031). The levels of Zinc and Magnesium in the serum of obese diabetic patients had a positive correlation among them (r=0.565#; p<0.001). TAG/HDL ratio a measure of small dense LDL is positively correlated with LDL in both groups (r=0.881 and 0.912) with p value<0.001 for both.

CONCLUSION

Correlation among Glycemic control, Insulin resistance, Thyroid hormones, divalent cations and dyslipidemia depict differential characteristics in obese and non-obese type2 diabetes with Thyroid comorbidity.

Thyroid function and ischemic heart disease: a Mendelian randomization study

To clarify the role of thyroid function in ischemic heart disease (IHD) we assessed IHD risk and risk factors according to genetically predicted thyroid stimulating hormone (TSH), free thyroxine (FT4) and thyroid peroxidase antibody (TPOAb) positivity. Separate-sample instrumental variable analysis with genetic instruments (Mendelian randomization) was used in an extensively genotyped case (n = 64,374)-control (n = 130,681) study, CARDIoGRAMplusC4D. Associations with lipids, diabetes and adiposity were assessed using the Global Lipids Genetics Consortium Results (n = 196,475), the DIAbetes Genetics Replication And Meta-analysis case (n = 34,380)-control (n = 114,981) study, and the Genetic Investigation of ANthropometric Traits (body mass index in 152,893 men and 171,977 women, waist-hip ratio in 93,480 men and 116,741 women). Genetically predicted thyroid function was not associated with IHD (odds ratio (OR) per standard deviation for TSH 1.05, 95% confidence interval (CI) 0.97 to 1.12; for FT4 1.01, 95% CI 0.91 to 1.12; for TPOAb positivity 1.10, 95% CI 0.83 to 1.46) or after Bonferroni correction with risk factors, except for an inverse association of FT4 with low-density lipoprotein-cholesterol. The associations were generally robust to sensitivity analyses using a weighted median method and MR Egger. This novel study provides little indication that TSH, FT4 or TPOAb positivity affects IHD, despite potential effects on its risk factors.