Effects of T4 replacement therapy on glucose metabolism in subjects with subclinical (SH) and overt hypothyroidism (OH)

Thyroid Hormone and Diabetes Mellitus Interplay: Making Management of Comorbid Disorders Complicated

Insulin and thyroid hormones play important roles in our body. Insulin helps regulate the glucose level while the thyroid hormones affect various cells and tissues, metabolizing protein, lipids, and glucose. Hyperthyroidism and thyrotoxicosis are potential hazards for type 2 diabetes mellitus. There is a high prevalence of hypothyroidism being more common compared to hyperthyroidism coexisting with diabetes mellitus. Thyroid hormones affect glucose metabolism through its action on peripheral tissues (gastrointestinal tract, liver, skeletal muscles, adipose tissue, and pancreas). High-level thyroid hormone causes hyperglycemia, upregulation of glucose transport, and reduction in glycogen storage. The reverse is observed during low levels of thyroid hormone along with insulin clearance. The net result of thyroid disorder is insulin resistance. Type 2 diabetes mellitus can downsize the regulation of thyroid stimulating hormones and impair the conversion of thyroxine to triiodothyronine in peripheral tissues. Furthermore, poorly managed type 2 diabetes mellitus may result in insulin resistance and hyperinsulinemia, contributing to the proliferation of thyroid tissue and an increase in nodule formation and goiter size. Although metformin proves advantageous for both type 2 diabetes mellitus and thyroid disorder patients, other antidiabetics like sulfonylureas, pioglitazone, and thiazolidinediones may have adverse effects on thyroid disorders. Moreover, antithyroid drugs such as methimazole can weaken glycemic control in individuals with diabetes. Thus, an interplay between both endocrinopathies is observed and individualized care and management of the disorder needs to be facilitated.

Characteristics of blood lipid and metabolic indicators in subclinical hypothyroidism patients: a retrospective study

Background

The characteristics of blood lipid and metabolic indicators were analyzed in patients with subclinical hypothyroidism (SCH), and the effect of type 2 diabetes mellitus (T2DM) on SCH patients was determined.

Methods

The physical examination data of 2,119 residents in a university community were retrospectively divided into 2 groups (SCH and non-SCH groups). Furthermore, the SCH group was divided into SCH-T2DM and SCH-non-T2DM subgroups, and the data between the groups were analyzed.

Results

The SCH group had significantly higher levels of triglycerides (p = 0.044), total cholesterol (p = 0.001), low-density lipoprotein cholesterol (p = 0.019), very low-density lipoprotein cholesterol (p = 0.044), 2-h plasma glucose (p = 0.023), and globulin (p = 0.000) compared to the non-SCH group. The SCH-T2DM group was older (p < 0.001), had a greater BMI (p = 0.028), a more rapid heart rate (p = 0.025), and a greater waist circumference (p < 0.001) than the SCH-non-T2DM group based on the subgroup analysis. The SCH-T2DM group had significantly higher dyslipidemia and dysglycemia levels than the SCH-non-T2DM group.

Conclusion

Patients with SCH with or without T2DM may have dyslipidemia and dysglycemia and should be evaluated accordingly.

A Vulnerability Index for Mitigation and Prevention of Diabetes Growth in India: A Disaggregated Analysis

OBJECTIVES

This study aimed to provide a vulnerability index (VI) for identifying vulnerable regions in different states of India, which may serve as a tool for state- and district-level planning for mitigation and prevention of diabetes growth in the country.

METHODS

Using data on 13 indicators under 4 domains, we generated domain-specific and overall VIs at state (36 states/union territories) and district levels (640 districts) using the percentile ranking method. The association of diabetes with individuals' socioeconomic status at different levels of regional vulnerability has also been observed through multivariable logistic regression models.

RESULTS

On a scale of 0 to 1, there are 13 states with an overall VI of >0.70, of which 5 states are from southern regions of India. A low VI has been achieved by socioeconomically backward states. We observed that prevalence rates and vulnerability levels for most of the top and bottom 11 states are in the same line. District-level analysis showed that the 20 most vulnerable and least vulnerable districts are mostly from coastal and socioeconomically backward states of the country, respectively. Furthermore, logistic regression revealed that rural adults and females are less likely to be diabetic in all vulnerability quartiles. The oldest, Muslims, wealthiest, widowed/deserted/separated, and those with schooling ≤12 years are significantly more likely to be diabetic than their counterparts.

CONCLUSION

The constructed VI is vital for identifying vulnerable areas and planners and policy-makers may use this comprehensive index and domain-specific VIs to prioritize resource allocation.

Epidemiological, Pathophysiological, and Clinical Considerations on the Interplay between Thyroid Disorders and Type 2 Diabetes Mellitus

Thyroid disorders (TD) and diabetes mellitus (DM) are the two endocrinopathies with the highest prevalence in the general population that frequently coexist. Thyroid dysfunction is more common in people with type 2 diabetes mellitus (T2DM) compared to normoglycemic individuals. Untreated TD can impair glycemic control, increasing the risk of diabetes complications. Hyperinsulinemia can affect the morphology of the thyroid gland by promoting the proliferation of thyroid tissue and increasing the size of thyroid nodules. Metformin can confer benefits in both endocrinopathies, while other antidiabetics, such as sulfonylureas, can negatively affect thyroid function. Animal and human observational data suggest an increased risk of medullary thyroid carcinoma after treatment with glucagon-like peptide-1 receptor agonists. However, randomized trials have so far been reassuring. Furthermore, some observational studies suggest an association between thyroid cancer and T2DM, especially in women. This narrative review aims to shed light on the epidemiological, pathophysiological, and clinical aspects of the interplay between TD and T2DM. Taking into account the important clinical implications of the coexistence of T2DM and TD, proper screening and management strategies are needed for both endocrinopathies to ensure optimal patient care.

Effects of levothyroxine replacement therapy on insulin resistance in patients with untreated primary hypothyroidism

OBJECTIVES

This study investigated the effects of levothyroxine replacement therapy on insulin resistance, lipid profile, and thyroid function in patients with untreated primary hypothyroidism. 105 patients with hypothyroidism with indication for levothyroxine replacement were enrolled in the present study. Insulin, fasting blood glucose and lipid profile were assessed at the beginning of diagnosis and three months after levothyroxine replacement. Insulin resistance was calculated by hemostasis model assessment of insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI).

RESULTS

Our data revealed a significant reduction in body mass index (27.18 ± 4.27 versus 26.81 ± 4.18 kg/m2, p = 0.028), cholesterol (199.79 ± 37.61 versus 178.10 ± 32.25 mg/dl, p < 0.001), triglyceride (160.41 ± 71.86 versus 146 ± 61.11 mg/dl, p = 0.012), low density lipoprotein-cholesterol (123.54 ± 30.7 versus 107.08 ± 26.98 mg/dl, p < 0.001), fasting insulin (8.91 ± 3.92 versus 8.05 ± 2.65 mIU/l, p < 0.001), and thyroid stimulating hormone (47.47 ± 3.4 versus 2.22 ± 1.84 µIU/ml, p < 0.001) levels before and after drug intervention. However, no statistical differences were observed in HOMA-IR, QUICKI, and high density lipoprotein-cholesterol. In conclusion, in patients with untreated primary hypothyroidism, levothyroxine replacement therapy based on HOMA-IR and QUICKI did not improve insulin resistance; however, lipid profile was significantly improved following levothyroxine administration.

TRIAL REGISTRATION

This study was registered in the Iranian Registry of Clinical Trials (IRCT) with ID number: IRCT20130610013612N10 on the date 2019-09-02.

The Impact of Hypothyroidism on Diabetes Mellitus and Its Complications: A Comprehensive Review

Diabetes mellitus (DM) is one of the most prevalent metabolic disorders in the world and is characterized by excessive blood glucose levels, which lead to deranged carbohydrate, protein, and lipid metabolisms. At its core, DM is an impairment of insulin metabolism, leading to a plethora of clinical features. The thyroid gland is another vital cog in the wheel of the endocrine system, and the hormones synthesized by it are heavily involved in the control of the body's metabolism. Hypothyroidism is a state in which thyroid hormones are deficient due to various factors and is characterized by a metabolically hypoactive state. Together, insulin, implicated in DM, and thyroid hormones engage in an intricate dance and serve to regulate the body's metabolism. It is imperative to explore the relationship between these two common endocrine disorders to understand their clinical association and mold treatments specific to patients in which they coexist. Both type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) have been shown to have an increased association with hypothyroidism, especially in patients with risk factors including female sex, hyperlipidemia, obesity, and anemia. This review also explores DM's macrovascular and microvascular complications and their association with hypothyroidism. It is of great use to screen for hypothyroidism in diabetic patients. Specific protocols, especially for patients at an elevated risk, provide improved quality of life to patients affected by this highly prevalent disease.

Type 1 Diabetes Mellitus and Autoimmune Diseases: A Critical Review of the Association and the Application of Personalized Medicine

Type 1 Diabetes Mellitus (T1DM) is a common hyperglycemic disease characterized by the autoimmune destruction of insulin-producing beta cells of the pancreas. Various attempts have been made to understand the complex interplay of genetic and environmental factors which lead to the development of the autoimmune response in an individual. T1DM is frequently associated with other autoimmune illnesses, the most common being autoimmune thyroid disorders affecting more than 90% of people with T1D and autoimmune disorders. Antithyroid antibodies are present in around 20% of children with T1D at the start of the illness and are more frequent in girls. Patients with T1DM often have various other co-existing multi-system autoimmune disorders including but not limited to thyroid diseases, parathyroid diseases, celiac disease, vitiligo, gastritis, skin diseases, and rheumatic diseases. It is a consistent observation in clinics that T1DM patients have other autoimmune disorders which in turn affect their prognosis. Concomitant autoimmune illness might affect diabetes care and manifest itself clinically in a variety of ways. A thorough understanding of the complex pathogenesis of this modern-day epidemic and its association with other autoimmune disorders has been attempted in this review in order to delineate the measures to prevent the development of these conditions and limit the morbidity of the afflicted individuals as well. The measures including antibody screening in susceptible individuals, early identification and management of other autoimmune disorders, and adoption of personalized medicine can significantly enhance the quality of life of these patients. Personalized medicine has recently gained favor in the scientific, medical, and public domains, and is frequently heralded as the future paradigm of healthcare delivery. With the evolution of the ‘omics’, the individualization of therapy is not only closer to reality but also the need of the hour.

Type 2 Diabetes Mellitus Coincident with Clinical and Subclinical Thyroid Dysfunctions Results in Dysregulation of Circulating Chemerin, Resistin and Visfatin

The alterations of circulating adipocytokines have been reported in thyroid diseases or type 2 diabetes mellitus (T2DM), but such data in T2DM coincident with clinical and subclinical thyroid-dysfunctions are limited, and remain to be investigated. We studied the changes in serum chemerin, resisitin and visfatin in T2DM patients with thyroid dysfunctions, and their association with inflammatory and insulin resistance-markers. A total of 272 female and male Iranian participants were selected and divided into six groups: the euthyroid group, T2DM, T2DM coincident with clinical and sub clinical hypothyroidism (SC-HO, and C-HO), and T2DM coincident with clinical and sub clinical hyperthyroidism (SC-HR, C-HR).Demographic characteristics, serum levels of adipocytokines, thyroid hormones, inflammatory factors (IL1-β, IL-6 and CRP) and insulin resistance-markers were determined in all participants. T2DM patients with clinical thyroid dysfunctions showed higher levels of circulating resistin, visfatin, chemerin and inflammatory factors, compared with the T2DM group and T2DM coexisted with subclinical thyroid diseases. No significant differences were observed in circulating adipocytokines and inflammatory markers between T2DM coexisting with subclinical thyroid diseases and those without thyroid dysfunctions. Our results revealed that clinical thyroid dysfunction in T2DM patients was associated with elevated levels of circulating resistin, chemerin, visfatin and inflammatory factors, while no such alteration was detected in T2DM coincident with subclinical thyroid dysfunction.

Update on subclinical thyroid dysfunction

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Differences in levothyroxine action on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity between metformin- and myo-inositol-treated women with autoimmune subclinical hypothyroidism

WHAT IS KNOWN AND OBJECTIVE

Insulin resistance impairs the impact of levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity. Both metformin and myo-inositol were found to improve insulin sensitivity and to reduce thyrotropin levels in individuals with hypothyroidism. The aim of the present study was to compare the effect of levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity between women receiving metformin and myo-inositol.

METHODS

The study included two groups of women with autoimmune hypothyroidism, treated for at least 6 months with either metformin (group A; n = 25) or myo-inositol (group B; n = 25). Both groups were matched for age, insulin sensitivity, hormone levels and antibody titers. For the following 6 months, all women received levothyroxine. Plasma levels of glucose, insulin, thyrotropin, free thyroid hormones, prolactin, 25-hydroxyvitamin D and high-sensitivity C-reactive protein (hsCRP), as well as titers of thyroid peroxidase and thyroglobulin antibodies were assessed at the beginning and at the end of the study.

RESULTS AND DISCUSSION

At baseline there were not differences between the study groups. Although levothyroxine reduced thyrotropin levels, increased free thyroid hormone levels and decreased antibody titers in both study groups, these effects were more pronounced in group A than group B. Only in group A, levothyroxine increased 25-hydroxyvitamin D, decreased hsCRP and improved insulin sensitivity. The impact of levothyroxine on thyrotropin and free thyroid hormones correlated with treatment-induced changes in insulin sensitivity, antibody titers, 25-hydroxyvitamin D and hsCRP.

WHAT IS NEW AND CONCLUSION

The present study suggests that the impact of levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity is stronger in women receiving metformin than in women treated with myo-inositol.

High First Trimester Levels of TSH as an Independent Risk Factor for Gestational Diabetes Mellitus: A Retrospective Cohort Study

Although numerous articles have found an association between alterations in thyroid function and the risk of gestational diabetes mellitus (GDM), other studies have failed to demonstrate this association. This may be due to the different cut-off points used to define subclinical hypothyroidism. We aim to clarify the role of thyroid stimulating hormone (TSH) level in GDM within pregnant women with normal free thyroxine (fT4) levels. This retrospective cohort study was performed in 6775 pregnant women. The association between TSH and GDM was assessed by bivariate and multivariate logistic regression. Pregnant women with subclinical hypothyroidism are at significantly greater risk for GDM when compared with euthyroid pregnant women (OR = 1.85; 95% CI = 1.36–2.52). We have also observed that TSH levels increase the risk of GDM within euthyroid pregnant women, since the TSH levels between 2.5 and 4.71 showed a higher risk of GDM than those whose TSH levels are between 0.31 and 2.49 (OR = 1.54; 95% CI = 1.28–1.84). In addition, pregnant women with positive thyroid antibodies have almost 2.5 times the risk of developing GDM (OR = 2.47; 95% CI = 1.57–3.89). Our results support that in pregnant women with normal fT4 levels, higher first trimester TSH level implies a higher risk of GDM.

Hypothyroidism And Gestational Diabetes Mellitus: Is There A Relationship?

Background and Objective — Subclinical gestational hypothyroidism (SGH) and gestational diabetes mellitus (GDM) constitute two most common endocrine pathologies encountered during pregnancy. SGH and GDM have common pathophysiological mechanisms, being interrelated pathological conditions that are capable of complicating the course of pregnancy, labor and the postpartum period both on the part of the mother and on the part of the fetus. We aimed to analyze the relationship between these pathologies and to assess the risk of developing GDM against the background of hypothyroidism. Materials and Methods — the study included 200 pregnant women observed at the Perinatal Center of the Maternity Hospital the Bauman State Clinical Hospital No. 29 during 2018-2020. The main group consisted of 133 women who visited the perinatal center for hypothyroidism (both SGH and primary hypothyroidism, detected prior to pregnancy); the control group comprised 67 women without endocrine pathology. Both groups were comparable in terms of age, height, weight, and the number of pregnancies in the anamneses. The main group received levothyroxine sodium therapy with the achievement of the target trimester-specific level of thyroid-stimulating hormone (TSH). The criteria for the diagnosis of SGH were the TSH level above 2.5 μIU/mL in combination with an enlarged titer of antithyroid antibodies and/or a burdened medical history of thyroid pathology, or the TSH level above 4.0 μIU/mL in the absence of antithyroid antibodies [1]. The diagnosis of GDM was established on the basis of fasting hyperglycemia (≥5.1 mmol/L), or based on the results of an oral glucose tolerance test (OGTT) with 75 g of glucose: fasting glucose level of ≥5.1 mmol/L; the concentration 1 hour after glucose intake ≥10.0 mmol/L; the content 2 hours after glucose intake ≥8.5 mmol/l) [2]. In both groups, the frequency of developing GDM, the timing of diagnosis, and the need for insulin therapy were evaluated. Statistical data processing was carried out using the StatTech v. 2.1.0 software. Quantitative indicators were assessed for compliance with the normal distribution via Shapiro-Wilk criterion or Kolmogorov-Smirnov criterion. Intergroup comparison was performed using Mann-Whitney U test or Pearson’s chi-squared test. Results — We discovered that among women with a burdened family history of thyroid pathology and diabetes mellitus, as well as with thyroid pathology prior to pregnancy, the prevalence of hypothyroidism was higher. The presence of thyroid pathology in the anamnesis of pregnant women was associated with an earlier diagnosis of hypothyroidism. We revealed a significant difference in the prevalence of GDM between two groups of subjects. The chances of detecting GDM in the hypothyroidism group were 8.6 times higher than in the euthyroidism group. The threshold level of TSH for the first trimester, predicting the development of GDM, was identified. The sensitivity and specificity of the model were 71.4% and 63.1%, respectively. Conclusion — Hypofunction of the thyroid and GDM are interrelated endocrine pathologies. In the presence of hypothyroidism (both primary and SGH), GDM develops significantly more often. The level of TSH in the first trimester ≥2.7 μIU/mL amplifies the chance of developing GDM by over 8 times; hence, it could be considered a signal for timely prevention and detection of this pathology.

Selenium and Selenoproteins at the Intersection of Type 2 Diabetes and Thyroid Pathophysiology

Type 2 diabetes (T2D) is considered one of the largest global public-health concerns, affecting approximately more than 400 million individuals worldwide. The pathogenesis of T2D is very complex and, among the modifiable risk factors, selenium (Se) has recently emerged as a determinant of T2D pathogenesis and progression. Selenium is considered an essential element with antioxidant properties, and is incorporated into the selenoproteins involved in the antioxidant response. Furthermore, deiodinases, the enzymes responsible for homeostasis and for controlling the activity of thyroid hormones (THs), contain Se. Given the crucial action of oxidative stress in the onset of insulin resistance (IR) and T2D, and the close connection between THs and glucose metabolism, Se may be involved in these fundamental relationships; it may cover a dual role, both as a protective factor and as a risk factor of T2D, depending on its basal plasma concentration and the individual’s diet intake. In this review we discuss the current evidence (from experimental, observational and randomized clinical studies) on how Se is associated with the occurrence of T2D and its influence on the relationship between thyroid pathophysiology, IR and T2D.

Effects of hypothyroidism on the female pancreas involve the regulation of estrogen receptors

This study aimed to investigate the impact of short-time hypothyroidism on the expression of aromatase, estrogen receptors (ERα, β), and GPR30 in the pancreas of female rabbits. The formation of new islets and the expression of insulin, GLUT4, and lactate dehydrogenase (LDH) were also analyzed. This purpose is based on actions that thyroid hormones and estrogens have on β-cells differentiation, acinar cell function, and insulin secretion. Twelve Chinchilla-breed adult virgin female rabbits were divided into control (n = 6) and hypothyroid (n = 6; methimazole 10 mg/kg for 30 days) groups. In the complete pancreas, expressions of aromatase and estrogen receptors, as well as proinsulin, GLUT4, and LDH were determined by western blot. Characteristics of islets were measured in slices of the pancreas with immunohistochemistry for insulin. Islet and acinar cells express aromatase, ERα, ERβ, and GPR30. Hypothyroidism increased the expression of ERα and diminished that for aromatase, ERβ, and GPR30 in the pancreas. It also promoted a high number of extra small islets (new islets) and increased the expression of proinsulin and GLUT4 in the pancreas. Our results show that actions of thyroid hormones and estrogens on β-cells neogenesis, acinar cell function, and synthesis and secretion of insulin are linked. Thus, the effects of hypothyroidism on the pancreas could include summatory actions of thyroid hormones plus estrogens. Our findings indicate the importance of monitoring estrogen levels and actions on the pancreas of hypothyroid women, particularly when serum estrogen concentrations are affected such as menopausal, pregnant, and those with contraceptive use.

Insulin resistance attenuates the impact of levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity in women with autoimmune subclinical hypothyroidism

Subjects with both subclinical hypothyroidism and autoimmune thyroiditis are frequently diagnosed with metabolic syndrome. The purpose of the current study was to investigate whether insulin sensitivity determines levothyroxine action on thyroid antibody titres and hypothalamic-pituitary-thyroid axis activity in young women with autoimmune subclinical hypothyroidism. The study population consisted of three age-, thyroid antibody- and thyrotropin-matched groups of women with autoimmune subclinical hypothyroidism: metformin-naive women with insulin resistance (group A, n=31), women receiving metformin treatment because of insulin resistance (group B, n=32), as well as metformin-naive women with normal insulin sensitivity (group C, n=35). Throughout the study, all subjects were treated with levothyroxine. Titres of thyroid peroxidase and thyroglobulin antibodies, as well as circulating levels of glucose, insulin, lipids, thyrotropin, free thyroid hormones, prolactin, high-sensitivity C-reactive protein (hsCRP) and 25-hydroxyvitamin D were determined at the beginning of the study and 6 months later. Except for two individuals, all patients completed the study. At baseline, group A differed from groups B and C in circulating levels of glucose, HDL-cholesterol, triglycerides, hsCRP, 25-hydroxyvitamin D and the homeostatic model assessment 1 of insulin resistance (HOMA1-IR). Although levothyroxine reduced thyroid antibody titres, decreased thyrotropin levels and increased free thyroid hormone levels in all studied groups, the effect on antibody titres and thyrotropin levels was more pronounced in groups B and C than in group A. The impact of levothyroxine on thyroid antibody titres correlated with baseline and treatment-induced changes in HOMA1-IR, thyrotropin, hsCRP and 25-hydroxyvitamin D. The results of the current study suggest that the impact of exogenous levothyroxine on thyroid autoimmunity and hypothalamic-pituitary-thyroid axis activity is determined by insulin sensitivity.

The Effects of 8 Weeks of Levothyroxine Replacement Treatment on Metabolic and Anthropometric Indices of Insulin Resistance in Hypothyroid Patients

BACKGROUND

Insulin resistance (IR) is an independent cardiovascular risk factor. IR predisposes to metabolic syndrome and diabetes. Meanwhile, little evidence exists about the effect of levothyroxine replacement treatment (LRT) on IR in hypothyroid patients.

OBJECTIVE

To investigate metabolic and anthropometric indices of IR in hypothyroid patients before and after 8 weeks of LRT.

METHODS

This pre-post study evaluated the 8 weeks outcomes of LRT on 66 patients with recently diagnosed hypothyroidism. Outcome measures included body mass index (BMI), waist circumferences (WC), waist to hip ratio (WHR), waist to height ratio (WHtR), body fat percent (BF%), free thyroxin (FT4), triglyceride (TG), low density lipoprotein (LDL), fasting plasma levels of glucose (FPG) and insulin. Sex- specific cut offs of two metabolic indices i.e. the triglyceride-glucose (TyG) and the homeostasis model assessment (HOMA) were used for IR diagnosis. The changes in TyG and HOMA were also compared after LRT.

RESULTS

Participants were overt and subclinical hypothyroidism 71% and 29%, respectively. After LRT the mean values of the following anthropometric indices significantly decreased: weight (79.61 vs. 78.64), BMI (29.53 vs. 29.2), WC (98.25 vs. 97.39) and BF% (35.34 vs. 34.95). After LRT the HOMA and TyG had no significant changes relative to their initial values. Also, IR that was determined on the basis of these metabolic indices more commonly observed in participants.

CONCLUSION

Despite decreasing some anthropometric indices, the diagnosis of IR based on metabolic indices increased following 8 weeks LRT in hypothyroid cases.

An Analysis of Glucose Effectiveness in Subjects With or Without Type 2 Diabetes via Hierarchical Modeling

Glucose effectiveness, defined as the ability of glucose itself to increase glucose utilization and inhibit hepatic glucose production, is an important mechanism maintaining normoglycemia. We conducted a minimal modeling analysis of glucose effectiveness at zero insulin (GEZI) using intravenous glucose tolerance test data from subjects with type 2 diabetes (T2D, n=154) and non-diabetic (ND) subjects (n=343). A hierarchical statistical analysis was performed, which provided a formal mechanism for pooling the data from all study subjects, to yield a single composite population model that quantifies the role of subject specific characteristics such as weight, height, age, sex, and glucose tolerance. Based on the resulting composite population model, GEZI was reduced from 0.021 min-1 (standard error - 0.00078 min-1) in the ND population to 0.011 min-1 (standard error - 0.00045 min-1) in T2D. The resulting model was also employed to calculate the proportion of the non-insulin-dependent net glucose uptake in each subject receiving an intravenous glucose load. Based on individual parameter estimates, the fraction of total glucose disposal independent of insulin was 72.8% ± 12.0% in the 238 ND subjects over the course of the experiment, indicating the major contribution to the whole-body glucose clearance under non-diabetic conditions. This fraction was significantly reduced to 48.8% ± 16.9% in the 30 T2D subjects, although still accounting for approximately half of the total in the T2D population based on our modeling analysis. Given the potential application of glucose effectiveness as a predictor of glucose intolerance and as a potential therapeutic target for treating diabetes, more investigations of glucose effectiveness in other disease conditions can be conducted using the hierarchical modeling framework reported herein.

Standard hypothyroid treatment did not restore proper metabolic response to carbohydrate

PURPOSE

Hypothyroidism is associated with a lower metabolic rate, impaired glucose tolerance, and increased responsiveness of sympathetic nervous system to glucose ingestion. The Levothyroxine (LT4) monotherapy is the standard treatment for hypothyroidism; however to what extent this treatment restores the patients' metabolism has not been verified. The aim of this study was to test the hypothesis that standard LT4 therapy may not restore proper metabolic response to carbohydrate ingestion.

METHODS

Energy expenditure, glucose tolerance, and catecholamine response to glucose ingestion were compared in 18 subjects with pharmacologically compensated hypothyroidism (PCH) and controls, at baseline and during oral glucose tolerance test conditions.

RESULTS

Metabolic rate was significantly lower in PCH (P < 0.0001). Glucose tolerance was decreased in this group with no differences in insulin resistance indicators between both groups. Adrenergic activity (P < 0.05) as well as adrenergic reaction to glucose ingestion (P < 0.001) were stronger in PCH.

CONCLUSIONS

Standard treatment for hypothyroidism does not restore the normal metabolic reaction to carbohydrate which is observed in healthy people.

Consequences of Iodine Deficiency and Excess in Pregnancy and Neonatal Outcomes: A Prospective Cohort Study in Rio de Janeiro, Brazil

Background: Insufficient or excessive iodine intake during gestation may compromise adaptive mechanisms in maternal thyroid function and lead to adverse pregnancy outcomes. In this context, we aimed to study the effects of maternal iodine status in the first and third trimesters of gestation on obstetric and neonatal outcomes in an iodine-sufficient population in Rio de Janeiro, Brazil. Methods: A total of 214 pregnant women in the first trimester of gestation were enrolled and prospectively followed until delivery between 2014 and 2017. All participants were ≥18 and ≤35 years, had a spontaneous single pregnancy, and had no history of thyroid or other chronic diseases, nor were they taking iodine-containing supplements at enrollment. In the first trimester, we obtained clinical information and determined thyroid function and the urinary iodine concentration (UIC) of the participants. Thyroid function and UIC were reassessed in the third trimester. Iodine status was determined by the median of UIC obtained from six urine spot samples by the inductively coupled plasma mass spectrometry method. Pregnancy and neonatal outcomes and delivery information were obtained from medical records. Results: The median UIC in the whole population was 219.7 μg/L. The prevalence of UIC <150 μg/L was 17.2%, and 38.7% had UIC ≥250 μg/L. Gestational diabetes (GDM) was higher in the group with UIC 250-499 μg/L (n = 77) compared with the group with UIC 150-249 μg/L (n = 94) (20.3% vs. 9.7%, p < 0.05). Ultimately, UIC ≥250 μg/L was an independent risk factors for GDM (relative risk [RR] = 2.9 [confidence interval, CI = 1.1-7.46], p = 0.027) and hypertensive disorders of pregnancy (HDP) (RR = 4.6 [CI = 1.1-18.0], p = 0.029). Among 196 live-born newborns, lower birth length was observed in infants whose mothers had UIC <150μg/L (n = 37) in the first trimester compared with those with UIC 150-249 μg/L (n = 86) (median interquartile range: 48.0 [2.2] vs. 49.0 [4.0] cm, p = 0.01). Maternal UIC <150 μg/L was negatively associated with birth length of newborns (Exp (B) = 0.33 [CI = 0.1-0.9], p = 0.03). Conclusions: In a population whose median iodine intake is sufficient, extensive individual variation occurs. Such abnormalities are associated with increased GDM and HDP when UIC is ≥250 μg/L, and lower infant birth length when UIC is <150 μg/L.

Low-free triiodothyronine is associated with poor prognosis of portal hypertension in cirrhosis

BACKGROUND AND AIMS

The role of thyroid function in the portal hypertension development and prognosis remains unclear. This study aimed to investigate the correlation between serum-free triiodothyronine (fT3) levels and the outcomes of cirrhotic portal hypertension.

METHODS

A total of 385 cirrhotic patients with confirmed portal hypertension underwent computed tomography angiography and thyroid function test at a tertiary care referral center from January 2009 to December 2017. The patients were assigned to the low-fT3 (n = 98) and normal-fT3 groups (n = 287).

RESULTS

Child-Pugh (8.88 ± 0.22 vs. 7.09 ± 0.12, P < 0.001) and model for end-stage liver disease (MELD) scores (14.75 ± 0.57 vs. 10.59 ± 0.23, P < 0.001) significantly increased in the low-fT3 group. The hemoglobin level correlated with fT3 (R = 0.299, P < 0.0001) and fT4 (R = 0.310, P < 0.0001), while only fT3 significantly correlated with the albumin level (R = 0.537, P < 0.001). The Kaplan-Meier analysis indicated that the two-year survival rate was 74.51% in the low-fT3 group vs. 94.25% in the normal-fT3 group (P < 0.0001). The Cox regression analysis demonstrated that the serum level of fT3 [hazard ratio: 0.478; 95% confidence interval (CI) 0.391-0.758; P = 0.002] and prothrombin time (hazard ratio: 2.247; 95% CI: 1.316-3.838; P = 0.003) were independent prognostic factors in cirrhotic patients.

CONCLUSION

The low fT3 level was associated with poor prognosis and the progression of cirrhotic portal hypertension.

Relationship between Free Thyroxine and Islet Beta-cell Function in Euthyroid Subjects

Thyroid hormones have a specific effect on glucose-induced insulin secretion from the pancreas. We aimed to investigate the association between euthyroid hormones and islet beta-cell function in general population and non-treated type 2 diabetes mellitus (T2DM) patients. A total of 5089 euthyroid participants (including 4601 general population and 488 non-treated T2DM patients) were identified from a cross-sectional survey on the prevalence of metabolic diseases and risk factors in East China from February 2014 to June 2016. Anthropometric indices, biochemical parameters, and thyroid hormones were measured. Compared with general population, non-treated T2DM patients exhibited higher total thyroxine (TT4) and free thyroxine (FT4) levels but lower ratio of free triiodothyronine (T3):T4 (P<0.01). HOMA-β had prominently negative correlation with FT4 and positive relationship with free T3:T4 in both groups even after adjusting for age, body mass index (BMI) and smoking. When analyzed by quartiles of FT4 or free T3:T4, there were significantly decreased trend of HOMA-β going with the higher FT4 and lower free T3:T4 in both groups. Linear regression analysis showed that FT4 but not FT3 and free T3:T4 was negatively associated with HOMA-β no matter in general population or T2DM patients, which was independent of age, BMI, smoking, hypertension and lipid profiles. FT4 is independently and negatively associated with islet beta-cell function in euthyroid subjects. Thyroid hormone even in reference range could play an important role in the function of pancreatic islets.

Incretin levels in patients with hypothyroidism and the evaluation of incretin levels alterations with treatment

Background

Incretin hormones may influence the effects of thyroid hormones on insulin secretion, insulin resistance, and glucose metabolism. Thyroid hormones regulate insulin secretion, and the risk of diabetes was found to be associated with thyroid hormones.

Objectives

To determine whether incretin hormones influence the effects of thyroid hormones on insulin resistance and glucose metabolism.

Methods

A total of 26 patients were included in 2 groups consisting of 13 patients with hypothyroidism and 13 healthy controls. Levels of glucose, insulin, glucagon-like peptide 1 (GLP-1), and gastric inhibitory polypeptide (GIP) levels were measured in 0, 30, 60, 90, and 120th min during the oral glucose tolerance test in the control group and before and after thyroxine treatment in the hypothyroid group.

Results

In the hypothyroid group, waist circumference decreased after the euthyroid state was achieved (P = 0.026). No statistically significant differences were detected in the GLP-1 and GIP levels at baseline and 30, 60, 90, and 120 min between the hypothyroidism and control groups or after ensuring the euthyroid state in patients with hypothyroidism. Peak GLP-1 levels were observed at 30 min in the control group, whereas peak GLP-1 and GIP levels were detected at 90 min in the hypothyroidism group. After achieving the euthyroid state, peak GLP-1 and GIP levels were detected at 30 min as well.

Conclusion

In patients with hypothyroidism, the incretin hormones, especially the peak response of the incretin system, are significantly affected. Significant changes were observed in the incretin system by correcting hypothyroidism.

Thyroid dysfunction prevalence and relation to glycemic control in patients with type 2 diabetes mellitus

OBJECTIVE

It is usually difficult to clinically identify thyroid abnormalities in diabetics as features of thyroid dysfunction may simulate diabetes symptoms or complications. So, assessing thyroid dysfunction prevalence in patients with type 2 diabetes mellitus (DM) would help better control of DM and its complications. Several studies reported this prevalence, however, some included small sample size or lacked a control group. We aimed to determine thyroid dysfunction prevalence in diabetic patients as well as its relation to glycemic control.

METHODS

A cross-sectional study included 200 patients having type 2 DM and 200 apparently healthy controls. Each participant was tested for fasting and 2-h post-prandial blood glucose, glycated haemoglobin (HbA1C), thyroid function tests: thyroid-stimulating hormone (TSH), free tri-iodothyronine (FT3), free thyroxine (FT4), serum total cholesterol and triglycerides and thyroid antibodies; anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) for hypothyroidism only.

RESULTS

There was a significant increase in serum TSH and T3 levels in diabetics when compared with the controls, (P < 0.001, P = 0.001), respectively. Thyroid dysfunction was significantly more prevalent in patients with HbA1c ≥ 8%, (P = 0.0001), and in those having longer diabetes duration, (P < 0.001).

CONCLUSION

There was a higher prevalence of thyroid dysfunction among patients with type 2 DM. This dysfunction increased with the rise of HbA1c. This could suggest that poor glycemic control may have a role in the development of thyroid dysfunction in type 2 DM patients. Subclinical hypothyroidism was the most prevalent type of thyroid dysfunction in diabetic patients.

Thyroid Dysfunction and Diabetes Mellitus: Two Closely Associated Disorders

Thyroid dysfunction and diabetes mellitus are closely linked. Several studies have documented the increased prevalence of thyroid disorders in patients with diabetes mellitus and vice versa. This review critically discusses the different underlying mechanisms linking type 1 and 2 diabetes and thyroid dysfunction to demonstrate that the association of these two common disorders is unlikely a simple coincidence. We assess the current state of knowledge on the central and peripheral control of thyroid hormone on food intake and glucose and lipid metabolism in target tissues (such as liver, white and brown adipose tissue, pancreatic β cells, and skeletal muscle) to explain the mechanism linking overt and subclinical hypothyroidism to type 2 diabetes and metabolic syndrome. We also elucidate the common susceptibility genes and the pathogenetic mechanisms contributing to the autoimmune mechanism involved in the onset of type 1 diabetes mellitus and autoimmune thyroid disorders. An untreated thyroid dysfunction can impair the metabolic control of diabetic patients, and this association can have important repercussions on the outcome of both of these disorders. Therefore, we offer recommendations for the diagnosis, management, and screening of thyroid disorders in patients with diabetes mellitus, including the treatment of diabetic patients planning a pregnancy. We also discuss the major causes of failure to achieve an optimal management of thyroid dysfunction in diabetic patients and provide recommendations for assessing and treating these disorders during therapy with antidiabetic drugs. An algorithm for a correct approach of these disorders when linked is also provided.

CASE FINDING FOR HYPOTHYROIDISM SHOULD INCLUDE TYPE 2 DIABETES AND METABOLIC SYNDROME PATIENTS: A LATIN AMERICAN THYROID SOCIETY (LATS) POSITION STATEMENT

OBJECTIVE

Latin American Thyroid Society (LATS) Hypothyroidism Clinical Practice Guidelines recommend case finding of hypothyroid patients in multiple and different situations that agree with other Society guidelines. However, the detection of hypothyroidism in type 2 diabetes mellitus (T2DM) or metabolic syndrome (MetS) patients is not mentioned in particular. In the recent years, several basic and epidemiologic studies have appeared showing that a lower thyroid function and MetS/T2DM are associated. Hence, the aim of this review is to manifest the LATS position on the diagnosis of hypothyroidism in both MetS and T2DM patients.

METHODS

A search was made in PubMed using the following terms: "hypothyroidism" AND "diabetes" OR "metabolic syndrome." The most relevant studies describing the prevalence and complications due to hypothyroidism in both MetS and T2DM patients were selected.

RESULTS

The current document reviews new information from studies that have shown that the prevalence of hypothyroidism is higher in T2DM patients (odds ratio [OR], 3.45; 95% confidence interval [CI], 2.5 to 4.7) and that diabetic complications are more prevalent in subclinical hypothyroidism (ScH). The incidence of T2DM is 1.09-fold higher with each doubling of thyroid-stimulating hormone (TSH) mIU/L (95% CI, 1.06 to 1.12), and the incidence of prediabetes increases 15% (hazard ratio, 1.15; 95% CI, 1.04 to 1.26) in patients with TSH >5 mIU/L. Similarly, MetS is more prevalent in ScH compared to euthyroid individuals (OR, 1.31; 95% CI, 1.08 to 1.60).

CONCLUSION

Thyroid function is affected in MetS and T2DM, and hypothyroidism is more common in these patients. Diabetic complications are more frequent in ScH patients. Therefore, LATS now recommends aggressive case finding of hypothyroidism in both MetS and T2DM patients.

ABBREVIATIONS

CI = confidence interval; GLUT4 = glucose transporter 4; HOMA-IR = homeostatic model assessment for insulin resistance; HR = hazard ratio; LATS = Latin American Thyroid Society; MetS = metabolic syndrome; OR = odds ratio; ScH = subclinical hypothyroidism; T2DM = type 2 diabetes mellitus; T3 = triiodothyronine; T4 = thyroxine; TSH = thyroid-stimulating hormone.

Pathogenesis of hypothyroidism-induced NAFLD: Evidence for a distinct disease entity?

Nonalcoholic fatty liver disease (NAFLD), the most common liver disease worldwide, may be associated with primary hypothyroidism. However, the pathogenesis underlying such an association is complex and not completely understood. Here, we specifically discuss the pathogenic mechanisms potentially involved in hypothyroidism-induced NAFLD. To this end, we summarize the general pathophysiology of thyroid hormones (TH). Next, we analyze the published data from rodent studies by discussing whether hypothyroid rats may develop NAFLD via hyperphagia; whether mitochondria become energetically more efficient; what the overall energy balance is and if diversion of fatty substrates occurs; and the latest advancements in molecular pathogenesis brought about by metabolomics, cell imaging, lipophagy, autophagy and genetically engineered mouse models. Moreover, we discuss the data published regarding humans on the pathogenic role of TH, metabolic syndrome and other risk factors in hypothyroidism-related NAFLD as well as the putative mechanisms underlying the development of NAFLD-related hepatocellular carcinoma in hypothyroidism. In conclusion, although many research questions still remain unanswered, the pathophysiology of hypothyroidism-induced NAFLD makes this a potentially curable and distinct disease entity. However, further studies are needed to better elucidate the underlying mechanisms, and to ascertain whether treatment with either TH or thyromimetic agents improves NAFLD.

Insulin resistance and diabetes in hyperthyroidism: a possible role for oxygen and nitrogen reactive species

In addition to insulin, glycemic control involves thyroid hormones. However, an excess of thyroid hormone can disturb the blood glucose equilibrium, leading to alterations of carbohydrate metabolism and, eventually, diabetes. Indeed, experimental and clinical hyperthyroidism is often accompanied by abnormal glucose tolerance. A common characteristic of hyperthyroidism and type 2 diabetes is the altered mitochondrial efficiency caused by the enhanced production of reactive oxygen and nitrogen species. It is known that an excess of thyroid hormone leads to increased oxidant production and mitochondrial oxidative damage. It can be hypothesised that these species represent the link between hyperthyroidism and development of insulin resistance and diabetes, even though direct evidence of this relationship is lacking. In this review, we examine the literature concerning the effects of insulin and thyroid hormones on glucose metabolism and discuss alterations of glucose metabolism in hyperthyroid conditions and the cellular and molecular mechanisms that may underline them.

Jinlida Granules Improve Dysfunction of Hypothalamic-Pituitary-Thyroid Axis in Diabetic Rats Induced by STZ

Objective

We aim to explore the effects and mechanisms of Jinlida granules on the dysfunction of hypothalamic-pituitary-thyroid (HPT) axis in diabetic rats induced by streptozotocin.

Methods

A total of 48 SD rats were randomized into normal control group (NC, n = 6) and diabetic group (n = 42). Rats in diabetic group were randomly divided into diabetes mellitus (DM) control group, low, medium, and high doses of Jinlida group (JL, JM, and JH), medium dose of Jinlida plus Tongxinluo group (JM + T), metformin group (Met), and Saxagliptin group (Sax) (n = 6 in each group). Diabetic rats were obtained by intraperitoneal injection of streptozotocin and sacrificed at 8 weeks to examine the function of HPT axis.

Results

Levels of fasting blood glucose (P < 0.05), pIκB, TNFα (P < 0.05), pNF-κB, and IL-6 (P < 0.01) in liver tissue and TSHR mRNA expression (P < 0.01) in diabetic group were significantly increased, while levels of serum T3 and T4, thyroid hormone receptor (TR) mRNA and Dio1 mRNA in liver tissue, and sodium iodide symporter (NIS) mRNA in thyroid tissue in diabetic group were significantly decreased compared with those in NC group (P < 0.01). Among diabetic groups, level of fasting blood glucose in JH, JM + T and Met group was lower (P < 0.05) compared with DM group. However, levels of serum T3 and T4, TR mRNA in liver tissue, TSHR, and NIS mRNA in thyroid tissue in JH, JM + T, Met, and Sax group were significantly increased (P < 0.01) compared to DM group. In contrast, levels of Dio1 mRNA, pI-κB in Met and JM + T groups, pNF-κB in JH, JM + T, and Met group, and TNFα and IL-6 in JM, JH, JM + T, and Met group were significantly decreased (P < 0.05). HE staining showed reduced thyroid follicular epithelium and follicular area, as well as increased colloid area in DM group, indicating impaired synthesis, reabsorption, and secretory of TH in diabetes, which was significantly improved in JH, JM + T, and Met groups.

Conclusion

HPT axis dysfunction in DM could be significantly improved by Jinlida granules. The mechanism might be associated with the anti-inflammatory effects involving NF-κB pathway. Our findings suggested the potential benefit of Jinlida granules for patients with HPT axis dysfunction and DM, which was to be verified by more experimental and clinical studies.

Hypothyroidism and nonalcoholic fatty liver disease - a chance association?

Background Nonalcoholic fatty liver disease (NAFLD) defines the clinical-pathological spectrum of hepatic lipotoxicity, which may progress to hepatic fibrosis and its complications. Thyroid hormone is a master regulator of cell metabolism and body fat distribution. Whether hypothyroidism is associated or not with an increased risk of developing NAFLD and its fibrotic progression is both clinically and physiopathologically relevant. Indeed, answering this research question would carry major pathogenic and therapeutic implications. Method PubMed database was searched using relevant key-words such as hypothyroidism; NAFLD; nonalcoholic steatohepatitis; cirrhosis; hepatocellular carcinoma; epidemiology; pathogenesis; natural history. The epidemiological studies and the meta-analyses published so far were identified as well as those studies addressing the physiopathology underlying this association. Results Many observational studies have investigated the association between either subclinical or overt hypothyroidism and NAFLD. Data are conflicting: some original and meta-analytical studies demonstrated that hypothyroidism, (mainly subclinical hypothyroidism), was common, occurring in approximately 25% of individuals with imaging-defined or biopsy-proven NAFLD; other studies, however, failed to identify a significant association between hypothyroidism and NAFLD. Moreover, such an association is biologically plausible based on the specific physiopathological impact of thyroid hormone and thyroid stimulating hormone (TSH) on metabolism of hepatocytes and accumulation and distribution of body fat. Conclusions The findings from the present review support a significant association between primary hypothyroidism and risk of development and progression of NAFLD. However, further studies evaluating the relative importance of subclinical versus overt hypothyroidism as well as addressing the mechanisms underlying the association of hypothyroidism with NAFLD are eagerly awaited.

Assessment of glucose effectiveness from short IVGTT in individuals with different degrees of glucose tolerance

AIMS

Minimal model analysis of intravenous glucose tolerance test (IVGTT) data represents the reference method to assess insulin sensitivity (S_I) and glucose effectiveness (S_G) that quantify the insulin-dependent and insulin-independent processes of glucose disappearance, respectively. However, test duration (3 h) and need for modeling expertise limit the applicability of this method. Aim of this study was providing a simple predictor of S_G applicable to short test (1 h), as previously done with S_I.

METHODS

Three groups of subjects reflecting different glucose tolerance degrees underwent a 3 h IVGTT: subjects with normal glucose tolerance (NGT, n = 164), with defective glucose regulation (DGR, n = 191), and with type 2 diabetes (T2D, n = 39). Minimal model analysis provided reference S_G and its components at zero (GEZI) and basal (BIE) insulin. The simple predictor CS_G (calculated S_G) was described by the formula CS_G = α₀ + α₁ × K_G/G_peak, being K_G the glucose disappearance rate (between 10 and 50 min) and G_peak the maximum of the glucose curve during the test; α₀ and α₁ coefficients were provided by linear regression analysis.

RESULTS

CS_G and S_G showed a markedly significant relationship in the whole dataset (r = 0.72, p < 0.0001) and in the single groups (r = 0.70 in NGT, r = 0.71 in DGR and r = 0.70 in T2D, p < 0.0001 for all); α₁ × K_G/G_peak was significantly related to GEZI (r ≥ 0.60).

CONCLUSIONS

The interest for insulin-independent glucose disappearance is increasing, due to the recent availability of SGLT2 pharmacological agents, lowering glycemic levels without requiring insulin action. This study proposes a reliable predictor of S_G based on IVGTT lasting 1 h only, and not requiring mathematical modeling skills.

THYROID HORMONE REPLACEMENT REDUCES THE RISK OF CARDIOVASCULAR DISEASES IN DIABETIC NEPHROPATHY PATIENTS WITH SUBCLINICAL HYPOTHYROIDISM

OBJECTIVE

Patients with diabetic nephropathy (DMN) have an increased risk of cardiovascular disease (CVD). However, strategies to reduce this risk are limited. Thyroid hormone replacement therapy (THRT) in patients with hypothyroidism has been shown to reduce several surrogate markers of CVD. Therefore, we performed a study to determine if THRT would reduce CVD risk in patients with subclinical hypothyroidism (SCH) and DMN.

METHODS

This was a retrospective, nonrandomized study of patients with type 2 diabetes, DMN, and SCH. Those with known thyroid dysfunction or taking THRT at baseline were excluded. Patients receiving THRT for at least 180 days were included in the THRT group, while the remaining patients were assigned to the non-THRT group. The primary outcome was CVD events, which included coronary syndrome, cerebrovascular events, and peripheral artery diseases.

RESULTS

Among the 257 patients, 83 (32.3%) were in the THRT group. The mean ages were 62.7 ± 12.3 and 66.8 ± 12.4 years in the THRT and non-THRT groups, respectively. The corresponding numbers of male patients were 32 (40.0%) and 94 (53.1%). During a mean follow-up of 38.0 ± 29.2 months, 98 CVD events were observed. Acute coronary syndrome and cerebrovascular event prevalence rates were lower in the THRT group than the non-THRT group, but there was no difference for peripheral artery diseases. Multivariate Cox analysis revealed that THRT was independently associated with a decreased CVD event risk.

CONCLUSION

THRT may decrease the risk of CVD in DMN patients with SCH. Randomized trials are needed to verify this finding.

ABBREVIATIONS

CV = cardiovascular DMN = diabetic nephropathy eGFR = estimated glomerular filtration rate fT4 = free thyroxine HbA1c = glycosylated hemoglobin HR = hazard ratio hs-CRP = high-sensitivity C-reactive protein LDL-C = low-density lipoprotein cholesterol SCH = subclinical hypothyroidism T2DM = type 2 diabetes THRT = thyroid hormone replacement therapy TSH = thyroid-stimulating hormone.

The Roles of Thyroid and Thyroid Hormone in Pancreas: Physiology and Pathology

It is widely accepted that thyroid hormones (THs), secreted from the thyroid, play important roles in energy metabolism. It is also known that THs also alter the functioning of other endocrine glands; however, their effects on pancreatic function have not yet been reviewed. One of the main functions of the pancreas is insulin secretion, which is altered in diabetes. Diabetes, therefore, could be related to thyroid dysfunction. Earlier research on this subject focused on TH regulation of pancreas function (such as insulin secretion) or on insulin function through TH-mediated increase of energy metabolism. Afterwards, epidemiological investigations and animal test research found a link between autoimmune diseases, thyroid dysfunction, and pancreas pathology; however, the underlying mechanisms remain unknown. Furthermore, recent studies have shown that THs also play important roles in pancreas development and on islet pathology, both in diabetes and in pancreatic cancer. Therefore, an overview of the effects of thyroid and THs on pancreas physiology and pathology is presented. The topics contained in this review include a summary of the relationship between autoimmune thyroid dysfunction and autoimmune pancreas lesions and the effects of THs on pancreas development and pancreas pathology (diabetes and pancreatic cancer).

[Pharmacological approaches for correction of thyroid dysfunctions in diabetes mellitus]

Thyroid diseases are closely associated with the development of types 1 and 2 diabetes mellitus (DM), and as a consequence, the development of effective approaches for their treatment is one of the urgent problems of endocrinology. Traditionally, thyroid hormones (TH) are used to correct functions of the thyroid system. However, they are characterized by many side effects, such as their negative effect on the cardiovascular system as well as the ability of TH to enhance insulin resistance and to disturb insulin-producing function of pancreas, exacerbating thereby diabetic pathology. Therefore, the analogues of TH, selective for certain types of TH receptors, that do not have these side effects, are being developed. The peptide and low-molecular weight regulators of thyroid-stimulating hormone receptor, which regulate the activity of the thyroid axis at the stage of TH synthesis and secretion in thyrocytes, are being created. Systemic and intranasal administration of insulin, metformin therapy and drugs with antioxidant activity are effective for the treatment of thyroid pathology in types 1 and 2 DM. In the review, the literature data and the results of own investigations on pharmacological approaches for the treatment and prevention of thyroid diseases in patients with types 1 and 2 DM are summarized and analyzed.

High dose of radioactive iodine per se has no effect on glucose metabolism in thyroidectomized rats

PURPOSE

Thyroid concentrates radioactive iodine by sodium-iodide symporter; this is used for treating hyperthyroidism and thyroid cancer. Pancreas expresses NIS and radioactive iodine uptake may damage pancreatic beta-cells and predispose patients to type 2 diabetes. The aim of this study was to determine whether radioactive iodine is associated with glucose metabolism in thyroidectomized rats.

METHODS

Forty male Wistar rats were divided into four groups (n = 10/each); control, thyroidectomized, thyroidectomized-treated with 131-I (TX+I), and thyroidectomized-treated with 131-I and L-thyroxine (TX+I+T₄). At the end of study, serum fasting glucose, insulin, thyroid-stimulating hormone, and free tetraiodothyronine were measured, intraperitoneal glucose tolerance test was performed, and homeostasis model assessment-insulin resistance was calculated. In in vitro experiments, glucose-stimulated insulin secretion from pancreatic islets and sodium-iodide symporter mRNA expression in thyroid and islets were determined.

RESULTS

Compared to control group, free tetraiodothyronine was lower by 41 and 77% and thyroid-stimulating hormone was higher by 36 and 126% in thyroidectomized and TX+I groups, respectively. Compared to controls, rats in TX+I group had glucose intolerance as assessed using the area under curve of intraperitoneal glucose tolerance test (12,376 ± 542 vs. 20,769 ± 1070, P < 0.001) and L-thyroxine replacement therapy restored the value (14,286 ± 328.24) to near normal. Fasting insulin and homeostasis model assessment-insulin resistance were comparable in all groups, however fasting glucose was higher in TX+I group. In in vitro experiments, glucose-stimulated insulin secretion from islets did not differ between groups.

CONCLUSION

Radioactive iodine therapy per se had no effect on glucose metabolism, just intensified thyroid hormone deficiency and the alterations on glucose metabolism in thyroidectomized rats. L-thyroxine therapy restored the glucose intolerance observed in radioactive iodine-treated thyroidectomized rats.

TSH increment and the risk of incident type 2 diabetes mellitus in euthyroid subjects

PURPOSE

Thyroid function is known to influence glucose metabolism, and thyroid-stimulating hormone is the most useful parameter in screening for thyroid dysfunction. Therefore, the aim of this study was to investigate the incidence of type 2 diabetes according to baseline thyroid-stimulating hormone level and thyroid-stimulating hormone change in euthyroid subjects.

METHODS

We identified and enrolled 17,061 euthyroid subjects without diabetes among participants who had undergone consecutive thyroid function tests between 2006 and 2012 as a part of yearly health check-up program. Thyroid-stimulating hormone changes were determined by subtracting baseline thyroid-stimulating hormone level from thyroid-stimulating hormone level at 1 year before diagnosis of diabetes or at the end of follow-up in subjects who did not develope diabetes.

RESULTS

During 84,595 person-years of follow-up, there were 956 new cases of type 2 diabetes. Cox proportional hazards models showed the risk of incident type 2 diabetes was significantly increased with each 1 μIU/mL increment in TSH after adjustment for multiple confounding factors (hazard ratio = 1.13, 95% confidence interval: 1.07-1.20, P < 0.001). Compared with individuals in the lowest tertile (-4.08 to 0.34 μIU/mL), those in the highest thyroid-stimulating hormone change tertile (0.41-10.84 μIU/mL) were at greater risk for incident type 2 diabetes (hazard ratio = 1.25, 95% confidence interval: 1.05-1.48, P for trend = 0.011). However, baseline thyroid-stimulating hormone level and tertile were not associated with the risk for diabetes.

CONCLUSIONS

Prominent increase in thyroid-stimulating hormone concentration can be an additional risk factor for the development of type 2 diabetes in euthyroid subjects.

Correction of Hypothyroidism Leads to Change in Lean Body Mass without Altering Insulin Resistance

BACKGROUND

Hypothyroidism is associated with insulin resistance, dyslipidemia, and abnormal body composition. This study assessed changes in body composition and insulin resistance after thyroxine (T₄) replacement in overt hypothyroidism.

METHODS

In this prospective longitudinal study carried out in a tertiary care center, adult nondiabetic patients with overt hypothyroidism were rendered euthyroid on T₄. Anthropometry including skinfold thickness (SFT) at the triceps and subscapularis was recorded. Patients underwent testing for fasting plasma glucose, creatinine, serum insulin, T₄, thyrotropin (TSH) and body composition analysis by dual-energy X-ray absorptiometry (DEXA) both before and at 2 months after restoration to the euthyroid state.

RESULTS

Twenty-seven patients (20 female and 7 male) aged 35.3 ± 11.0 years (min-max: 17-59 years) with overt hypothyroidism were recruited. Serum T₄ at the time of recruitment was 48.9 ± 24.6 nmol/l (normal range = 64.4-142 nmol/l). All patients had TSH ≥50 µIU/l. Following treatment, there was a mean body weight reduction of 1.7 kg (p = 0.01). Waist circumference as well as triceps and subscapularis SFT decreased significantly (p < 0.001). There was no change in fat mass (FM), percentage of fat (%FM) or bone mineral content in any of the specified regions or in the body as a whole. In contrast, mean lean body mass (LBM) decreased significantly by 0.8 kg (p < 0.01) in the trunk and 1.3 kg (p < 0.01) in the whole body. Insulin resistance and level of glycemia were not affected by treatment with T₄.

CONCLUSION

LBM decreases significantly without affecting FM after correction of hypothyroidism. Insulin resistance was not influenced by T₄ treatment.

Induction of oxidative stress, suppression of glucose-induced insulin release, ATP production, glucokinase activity, and histomorphometric changes in pancreatic islets of hypothyroid rat

Thyroid hormones have important role in metabolism and impairment of glucose metabolism and insulin secretion has been shown in hypothyroid rats but the exact mechanisms for this defect are poorly understood. The aim of this study was to investigate the effect of hypothyroidism on oxidative stress parameters, insulin secretory pathway and histomorphometric changes of pancreas. In the isolated islets of the control and methimazole -treated hypothyroid insulin secretion and content, ATP production, Glucokinase, and hexokinase specific activity and kATP and L-type channels sensitivity were assayed. In order to determine oxidative stress parameters, antioxidant enzymes and lipid peroxidation were measured in pancreatic homogenates. Histomorphometric changes and histochemistry of the islet in both groups were compared. Results showed that plasma glucose and insulin concentration and their area under the curve during IPGTT in hypothyroid group were respectively higher and lower than the controls. In the hypothyroid islets, glucose stimulated insulin secretion, ATP production, hexokinase and glucokinase activities were decreased. Hypothyroid induced a significant increased lipid peroxidation, and decreased the antioxidant enzyme activity. Compared with the control group, insulin antibody positivity, the total volume of the pancreas, islets, and the total number as well as the mean volume of the beta cells were also significantly decreased in the hypothyroid group. These findings indicate that oxidative stress produced under hypothyroidism could have a role in progression of pancreatic β-cell dysfunction, reduced beta cell mass and decreased glucokinase activity, impairing glucose tolerance and insulin secretion.

Maternal subclinical hypothyroidsm and gestational diabetes mellitus: a meta-analysis

OBJECTIVE

The association between subclinical hypothyroidism (SCH) and gestational diabetes mellitus (GDM) is controversial. This review evaluates whether the risk of GDM is different in pregnant women with SCH compared to euthyroid pregnant women.

METHODS

A computerized search of the MEDLINE and EMBASE databases was conducted from their inceptions to July 2013 and was complemented with the perusal of the reference sections of the retrieved articles. Prespecified criteria were applied to assess eligibility, and standard meta-analytic methodology was employed for evidence synthesis.

RESULTS

Six cohort studies, reporting data on 35,350 pregnant women (1,216 women with SCH), were identified. The risk of GDM in pregnant women with SCH was found to be substantially higher compared to euthyroid pregnant women (5 studies, pooled unadjusted odds ratio [OR]: 1.35, 95% confidence interval [CI]: 1.05-1.75, I2: 41%, Harbord test P = .44). Similarly, the risk of GDM was estimated to be significantly higher in pregnant women with SCH when using adjusted estimates (3 studies, pooled adjusted OR: 1.39, 95% CI: 1.07-1.79, I2: 0%). Neither finding remained significant in sensitivity analyses.

CONCLUSION

A modestly increased risk of GDM might be present in pregnant women with SCH compared to euthyroid pregnant women. Assuming a 5% baseline risk of GDM and that SCH increases the risk of GDM by 50% (in odds) compared to a euthyroid population, then there would be 1 extra case of GDM in every 43 pregnant women with SCH. This preliminary finding warrants further investigation.

Prenatal Exposures to Multiple Thyroid Hormone Disruptors: Effects on Glucose and Lipid Metabolism

Background. Thyroid hormones (THs) are essential for normal human fetal development and play a major role in the regulation of glucose and lipid metabolism. Delivery of TH to target tissues is dependent on processes including TH synthesis, transport, and metabolism. Thyroid hormone endocrine disruptors (TH-EDCs) are chemical substances that interfere with these processes, potentially leading to adverse pregnancy outcomes. Objectives. This review focuses on the effects of prenatal exposures to combinations of TH-EDCs on fetal and neonatal glucose and lipid metabolism and also discusses the various mechanisms by which TH-EDCs interfere with other hormonal pathways. Methods. We conducted a comprehensive narrative review on the effects of TH-EDCs with particular emphasis on exposure during pregnancy. Discussion. TH imbalance has been linked to many metabolic processes and the effects of TH imbalance are particularly pronounced in early fetal development due to fetal dependence on maternal TH for proper growth and development. The pervasive presence of EDCs in the environment results in ubiquitous exposure to either single or mixtures of EDCs with deleterious effects on metabolism. Conclusions. Further evaluation of combined effects of TH-EDCs on fetal metabolic endpoints could improve advice provided to expectant mothers.

Conversion from Tacrolimus to Cyclosporine A Improves Glucose Tolerance in HCV-Positive Renal Transplant Recipients

Background

Calcineurin-inhibitors and hepatitis C virus (HCV) infection increase the risk of post-transplant diabetes mellitus. Chronic HCV infection promotes insulin resistance rather than beta-cell dysfunction. The objective was to elucidate whether a conversion from tacrolimus to cyclosporine A affects fasting and/or dynamic insulin sensitivity, insulin secretion or all in HCV-positive renal transplant recipients.

Methods

In this prospective, single-center study 10 HCV-positive renal transplant recipients underwent 2h-75g-oral glucose tolerance tests before and three months after the conversion of immunosuppression from tacrolimus to cyclosporine A. Established oral glucose tolerance test-based parameters of fasting and dynamic insulin sensitivity and insulin secretion were calculated. Data are expressed as median (IQR).

Results

After conversion, both fasting and challenged glucose levels decreased significantly. This was mainly attributable to a significant amelioration of post-prandial dynamic glucose sensitivity as measured by the oral glucose sensitivity-index OGIS [422.17 (370.82–441.92) vs. 468.80 (414.27–488.57) mL/min/m2, p = 0.005), which also resulted in significant improvements of the disposition index (p = 0.017) and adaptation index (p = 0.017) as markers of overall glucose tolerance and beta-cell function. Fasting insulin sensitivity (p = 0.721), insulinogenic index as marker of first-phase insulin secretion [0.064 (0.032–0.106) vs. 0.083 (0.054–0.144) nmol/mmol, p = 0.093) and hepatic insulin extraction (p = 0.646) remained unaltered. No changes of plasma HCV-RNA levels (p = 0.285) or liver stiffness (hepatic fibrosis and necroinflammation, p = 0.463) were observed after the conversion of immunosuppression.

Conclusions

HCV-positive renal transplant recipients show significantly improved glucose-stimulated insulin sensitivity and overall glucose tolerance after conversion from tacrolimus to cyclosporine A. Considering the HCV-induced insulin resistance, HCV-positive renal transplant recipients may benefit from a cyclosporine A-based immunosuppressive regimen.

Trial Registration

ClinicalTrials.gov NCT02108301

Hypothyroidism is a Risk Factor for New-Onset Diabetes: A Cohort Study

OBJECTIVE

To identify risk factors for the development of statin-associated diabetes mellitus (DM).

RESEARCH DESIGN AND METHODS

The study was conducted in two phases. Phase one involved high-throughput in silico processing of a large amount of biomedical data to identify risk factors for the development of statin-associated DM. In phase two, the most prominent risk factor identified was confirmed in an observational cohort study at Clalit, the largest health care organization in Israel. Time-dependent Poisson regression multivariable models were performed to assess rate ratios (RRs) with 95% CIs for DM occurrence.

RESULTS

A total of 39,263 statin nonusers were matched by propensity score to 20,334 highly compliant statin initiators in 2004-2005 and followed until the end of 2010. Within 59,597 statin users and nonusers in a multivariable model, hypothyroidism and subclinical hypothyroidism carried an increased risk for DM (RR 1.53 [95% CI 1.31-1.79] and 1.75 [1.40-2.18], respectively). Hypothyroidism increased DM risk irrespective of statin treatment (RR 2.06 [1.42-2.99] and 1.66 [1.05-2.64] in statin users and nonusers, respectively). Subclinical hypothyroidism risk for DM was prominent only upon statin use (RR 1.94 [1.13-3.34] and 1.20 [0.52-2.75] in statin users and nonusers, respectively). Patients with hypothyroidism treated with thyroid hormone replacement therapy were not at increased risk for DM.

CONCLUSIONS

Hypothyroidism is a risk factor for DM. Subclinical hypothyroidism-associated risk for DM is prominent only upon statin use. Identifying and treating hypothyroidism and subclinical hypothyroidism might reduce DM risk. Future clinical studies are needed to confirm the findings.

Low-normal thyroid function and the pathogenesis of common cardio-metabolic disorders

BACKGROUND

Subclinical hypothyroidism may adversely affect the development of cardiovascular disease (CVD). Less is known about the role of low-normal thyroid function, that is higher thyroid-stimulating hormone and/or lower free thyroxine levels within the euthyroid reference range, in the development of cardio-metabolic disorders. This review is focused on the relationship of low-normal thyroid function with CVD, plasma lipids and lipoprotein function, as well as with metabolic syndrome (MetS), chronic kidney disease (CKD) and nonalcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This narrative review, which includes results from previously published systematic reviews and meta-analyses, is based on clinical and basic research papers, obtained via MEDLINE and PubMed up to November 2014.

RESULTS

Low-normal thyroid function could adversely affect the development of (subclinical) atherosclerotic manifestations. It is likely that low-normal thyroid function relates to modest increases in plasma total cholesterol, LDL cholesterol and triglycerides, and may convey pro-atherogenic changes in lipoprotein metabolism and in HDL function. Most available data support the concept that low-normal thyroid function is associated with MetS, insulin resistance and CKD, but not with high blood pressure. Inconsistent effects of low-normal thyroid function on NAFLD have been reported so far.

CONCLUSIONS

Observational studies suggest that low-normal thyroid function may be implicated in the pathogenesis of CVD. Low-normal thyroid function could also play a role in the development of MetS, insulin resistance and CKD, but the relationship with NAFLD is uncertain. The extent to which low-normal thyroid function prospectively predicts cardio-metabolic disorders has been insufficiently established so far.

Low-normal thyroid function and novel cardiometabolic biomarkers

The concept is emerging that low-normal thyroid function, i.e., either higher thyroid-stimulating hormone or lower free thyroxine levels within the euthyroid reference range, could contribute to the development of atherosclerotic cardiovascular disease. It is possible that adverse effects of low-normal thyroid function on cardiovascular outcome may be particularly relevant for specific populations, such as younger people and subjects with high cardiovascular risk. Low-normal thyroid function probably relates to modest increases in plasma total cholesterol, low density lipoprotein cholesterol, triglycerides and insulin resistance, but effects on high density lipoprotein (HDL) cholesterol and non-alcoholic fatty liver disease are inconsistent. Low-normal thyroid function may enhance plasma cholesteryl ester transfer, and contribute to an impaired ability of HDL to inhibit oxidative modification of LDL, reflecting pro-atherogenic alterations in lipoprotein metabolism and HDL function, respectively. Low-normal thyroid function also confers lower levels of bilirubin, a strong natural anti-oxidant. Remarkably, all these effects of low-normal thyroid functional status appear to be more outspoken in the context of chronic hyperglycemia and/or insulin resistance. Collectively, these data support the concept that low-normal thyroid function may adversely affect several processes which conceivably contribute to the pathogenesis of atherosclerotic cardiovascular disease, beyond effects on conventional lipoprotein measures.

Euthyroid sick syndrome in children with diabetic ketoacidosis

OBJECTIVES

To investigate characteristics of euthyroid sick syndrome (ESS) in children with diabetic ketoacidosis (DKA).

METHODS

This retrospective study was carried out between May 2010 and April 2013 at the Pediatric Department of Shandong Provincial Hospital, Shandong University, Shandong, China. Diabetic ketoacidosis children were divided into 2 groups: euthyroidism (group one, n=30) and ESS (group 2, n=40). C-peptide, glycosylated hemoglobin (HbA1c), bicarbonate, anion gap (AG), free triiodothyronine (FT3), free thyroxine (FT4), and thyrotropin (TSH) levels were measured before and after 7 days of insulin treatment. Daily blood glucose (BG) profiles were recorded.

RESULTS

Glycosylated hemoglobin, AG, the mean daily BG, and fasting blood glucose levels were higher, and bicarbonate, FT3, FT4, and TSH levels were lower in group 2 than in group one (all p&lt;0.05). Free triiodothyronine (r=-0.593, p&lt;0.001) and FT4 (r=-0.402, p=0.001) were negatively correlated with HbA1c. Free triiodothyronine (r=-0.438, p&lt;0.001) and FT4 (r=-0.505, p&lt;0.001) were negatively correlated with AG, and FT3 (r=0.503, p&lt;0.001) and FT4 (r=0.448, p&lt;0.001) were positively correlated with bicarbonate.

CONCLUSION

Diabetic ketoacidosis children with ESS have poor diabetic control. Free thyroid hormones are associated with the severity of DKA.

Insulin resistance in hypothyroid patients under Levothyroxine therapy: a comparison between those with and without thyroid autoimmunity

Background

A chronic inflammation resulting from an imbalance between pro-inflammatory and anti-inflammatory cytokines in Hashimoto’s thyroiditis (HT) might be responsible for IR in hypothyroidism. This study was performed to investigate a probable association between autoimmune background of hypothyroidism and IR.

Methods

In this clinical study, 63 subjects with Hashimoto’s thyroiditis and 49 subjects with post-ablation hypothyroidism were enrolled. All the participants were euthyroid for more than one year through Levothyroxine therapy. Serum concentrations of Thyroid-stimulating Hormone (TSH), Free Thyroxin (FT4, FT3), Anti-Thyroid Peroxidase Antibodies (Anti-TPO Abs), Total Cholesterol (TC), HDL-Cholesterol (HDL-C), Triglyceride (TG), Fasting Blood Glucose (FBG), and insulin levels were measured and Oral Glucose Tolerance Test (OGTT) was performed for all of the subjects. Participants with anti TPO levels more than 1000 IU /ml were classified as having highly positive antibodies.

Results

No significant differences regarding to plasma insulin, glucose and lipid concentration, were detected between subjects with and without Hashimoto’s thyroiditis. However, subjects with highly positive Anti TPO Abs had higher prevalence of elevated fasting insulin level than those with lower titers of Anti TPO Abs and subjects without autoimmune background (94.1% vs. 62.8% and 71.4% respectively, P = 0.05). Subjects with highly positive titers of Abs also had a lower serum HDL-c levels than the rest of the subjects (40.6 ± 2.1 vs. 47.2 ± 1.7 and 47.4 ± 1.4, P = 0.04).

Conclusions

There is no obvious association between thyroid autoimmunity and metabolic indexes of hypothyroid patients. Only patients with Ani TPO antibody levels more than 1000 IU/ml may experience higher insulin level and less HDL-c with the same BMI.

Effects of levothyroxine treatment on insulin sensitivity, endothelial function and risk factors of atherosclerosis in hypothyroid women

OBJECTIVES

Contradictory results are encountered in literature regarding the effects of hypothyroidism on the risk factors of atherosclerosis. We aimed to explore the changes in atherosclerotic risk factors and insulin sensitivity before and after levothyroxine replacement therapy in women with primary hypothyroidism and compare with that of healthy controls.

PATIENTS AND METHODS

Twelve patients (mean age of 34±11.7years) without an evident disease except for primary hypothyroidism (TSH≥20mIU/L) and eleven euthyroid, age-matched (33.8±8.4years) female volunteers as controls were included. Baseline thyroid hormones, lipid parameters, homocysteine, fibrinogen levels were measured in both groups. Flow-mediated endothelial-dependent vasodilatation (FMD) method was used to evaluate endothelial dysfunction. Insulin sensitivity was assessed by M values based on euglycemic hyperinsulinemic clamp technique. The same measurements were performed after 6months of levothyroxine treatment and recovery of euthyroid state in hypothyroid patients.

RESULTS

Treatment reduced total cholesterol (P<0.005), LDL-cholesterol (P<0.005), lipoprotein(a) (P<0.01), fibrinogen (P<0.0001) and homocysteine (P<0.0005) levels. Treatment significantly improved M values of hypothyroid patients (3.68±1.53mg/kg.min vs 6.02±1.21mg/kg.min, P<0.0001) and FMD (9.1±3.7% vs 16.4±4.4%, hypothyroid vs euthyroid, P<0.0001). Significant correlations were found between M values and TSH (r=-0.6, P<0.005), fibrinogen (r=-0.53, P<0.01) measurements, free T3 (r=0.51, P<0.02) and free T4 (r=0.49, P<0.02) levels. FMD was significantly correlated with fibrinogen levels (r=-0.49, P<0.05).

CONCLUSION

Insulin resistance, endothelial dysfunction, atherosclerotic risk markers improves with treatment of hypothyroidism.

Treatment with thyroid hormone

Thyroid hormone deficiency can have important repercussions. Treatment with thyroid hormone in replacement doses is essential in patients with hypothyroidism. In this review, we critically discuss the thyroid hormone formulations that are available and approaches to correct replacement therapy with thyroid hormone in primary and central hypothyroidism in different periods of life such as pregnancy, birth, infancy, childhood, and adolescence as well as in adult patients, the elderly, and in patients with comorbidities. Despite the frequent and long term use of l-T4, several studies have documented frequent under- and overtreatment during replacement therapy in hypothyroid patients. We assess the factors determining l-T4 requirements (sex, age, gender, menstrual status, body weight, and lean body mass), the major causes of failure to achieve optimal serum TSH levels in undertreated patients (poor patient compliance, timing of l-T4 administration, interferences with absorption, gastrointestinal diseases, and drugs), and the adverse consequences of unintentional TSH suppression in overtreated patients. Opinions differ regarding the treatment of mild thyroid hormone deficiency, and we examine the recent evidence favoring treatment of this condition. New data suggesting that combined therapy with T3 and T4 could be indicated in some patients with hypothyroidism are assessed, and the indications for TSH suppression with l-T4 in patients with euthyroid multinodular goiter and in those with differentiated thyroid cancer are reviewed. Lastly, we address the potential use of thyroid hormones or their analogs in obese patients and in severe cardiac diseases, dyslipidemia, and nonthyroidal illnesses.

Different levels of thyroid hormones between impaired fasting glucose and impaired glucose tolerance: free T3 affects the prevalence of impaired fasting glucose and impaired glucose tolerance in opposite ways

CONTEXT

There is an association between thyroid disorders and diabetes mellitus.

OBJECTIVE

To investigate thyroid hormone levels in different glucose metabolic statuses, analyse relationships between thyroid hormone levels and different categories of prediabetes and metabolic parameters within a large euthyroid nondiabetic population.

METHODS

A total of 3328 subjects without diabetes or thyroid dysfunction were included in this cross-sectional study. Subjects were divided in to four groups [normal glucose tolerance (NGR), impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and combined glucose intolerance (CGI)] according to the results of oral glucose tolerance test. Participants were then divided into four groups according to the quartile of free T3 (FT3) in their blood.

RESULTS

Subjects with IFG had higher levels of FT3 and ratio of FT3 to FT4 (FT3/FT4), but lower level of free T4 (FT4) than subjects with IGT. FT3/FT4 was negatively associated with postprandial plasma glucose (PPG) [standardized β (β) = -0·087; P < 0·001]. The prevalence of IFG and CGI was increased with the level of FT3, while the prevalence of IGT was decreased with the level of FT3 (P for trend: <0·001, 0·003 and <0·001, respectively). FT3 was negatively associated with the risk of IGT (OR = 0·409, 95% CI 0·179-0·935), whereas FT4 was positively associated with the risk of IGT (OR = 1·296, 95% CI 1·004-1·673).

CONCLUSIONS

Free thyroid hormone levels were different between subjects with IFG and IGT. FT3 affects the prevalence of IFG and IGT in opposite ways. The difference in thyroid hormone levels may play an important role in the different pathological mechanisms of IFG and IGT.

Impaired oxidative endoplasmic reticulum stress response caused by deficiency of thyroid hormone receptor α

Thyroid hormone receptor α (TRα) is critical to postnatal pancreatic β-cell maintenance. To investigate the association between TRα and the survival of pancreatic β-cells under endoplasmic reticulum (ER) stress, the expression of endogenous TRα was inhibited by infection with an adenovirus expressing double-stranded short hairpin RNA against TRα (AdshTRα). In control adenovirus-infected pancreatic β-cells, palmitate enhanced the expression of activating transcription factor 4 (ATF4) and heme oxygenase 1, which facilitates adaptation to oxidative ER stress. However, in AdshTRα-infected pancreatic β-cells, palmitate did not induce ATF4-mediated integrated stress response, and oxidative stress-associated apoptotic cell death was significantly enhanced. TRα-deficient mice or wild-type mice (WT) were fed a high fat diet (HFD) for 30 weeks, and the effect of oxidative ER stress on pancreatic β-cells was analyzed. HFD-treated TRα-deficient mice had high blood glucose levels and low plasma insulin levels. In HFD-treated TRα-deficient mice, ATF4 was not induced, and apoptosis was enhanced compared with HFD-treated WT mice. Furthermore, the expression level of 8-hydroxydeoxyguanosine, an oxidative stress marker, was enhanced in the β-cells of HFD-treated TRα-deficient mice. These results indicate that endogenous TRα plays an important role for the expression of ATF4 and facilitates reduced apoptosis in pancreatic β-cells under ER stress.