Homeostatic Model Assessment-Insulin Resistance (HOMA-IR 2) in Mild Subclinical Hypothyroid Subjects

Thyroid-Stimulating Hormone and Thyroid Hormones and Incidence of Diabetes: Prospective Results of the Brazilian Longitudinal Study of Adult Health (ELSA-BRASIL)

Background: There are conflicting data regarding the association of thyroid function with incident diabetes. We prospectively investigated thyrotropin (TSH), free thyroxine (fT4), free triiodothyronine (fT3), and its conversion ratio (fT3:fT4) with the risk of developing diabetes in euthyroid subjects and those with subclinical thyroid dysfunction. Our hypothesis is that this relationship is a U-shaped curve since both subclinical thyroid diseases may be associated with diabetes. Methods: ELSA-Brasil is a highly admixed cohort study of 35-74 years old at baseline (2008-2010). Levels of TSH, fT4, fT3, and fT3:fT4 ratio were evaluated at baseline and incident diabetes was estimated over an 8.2-year follow-up (2017-2019). Diabetes was identified based on medical diagnosis, prescriptions, and laboratory tests. The risk of diabetes was evaluated according to quintiles of TSH, fT4, fT3, and fT3:fT4 ratio using Poisson regression with robust variance presented as relative risk (RR) with confidence interval [CI] of 95% after multivariable adjustment for sociodemographic and cardiovascular risk factors (reference third quintile), and as continuous variables. Results: We included 7948 participants (mean age, 50.2 [standard deviation 8.6] years; 54.4% female): 7177 euthyroid, 726 with subclinical hypothyroidism, and 45 with subclinical hyperthyroidism. Incidence of diabetes was 14.8%. No association was found for TSH, fT4, fT3, and fT3:fT4 ratio quintiles with incident diabetes. Using continuous variables, the increase of 1-unit (1-U) of fT4 decreased the risk of diabetes (RR 0.94 [CI 0.91-0.99]), while the increase of 1-U of the fT3:fT4 ratio increased the diabetes risk (RR 1.37 [CI 1.15-1.63]). The increase of 1-U of fT3 was associated with an increased risk of diabetes, but without significance after multivariable adjustment. In body mass index-stratified analysis, people with overweight or obesity presented a modest significantly higher risk of diabetes in the lowest quintile of fT4 (RR 1.04 [CI 1.01-1.07]) and an inverse association with incident diabetes in the first quintile of fT3:fT4 ratio (RR, 0.95 [CI 0.93-0.98]). The analyses using continuous variables presented similar findings. Conclusion: These findings suggest that fT4 and fT3 levels and the conversion rate might be additional risk factors associated with incident diabetes, especially in the presence of overweight or obesity. However, they need to be confirmed in future studies. (ClinicalTrials.gov Identifier: NCT02320461).

Effect of Subclinical Hypothyroidism on the Association between Hemoglobin A1c and Reduced Renal Function: A Prospective Study

Subclinical hypothyroidism (SCH) was reported to be associated with accelerating endothelial dysfunction, which is recognized as one of the upstream mechanisms that leads to glomerular injury (lower glomerular filtration rate (GFR)). SCH was also reported to be associated with hyperglycemia, which is associated with higher hemoglobin A1c (HbA1c) levels and induces endothelial dysfunction. Therefore, SCH status could influence the association between HbA1c and reduced eGFR. To clarify those associations, we conducted a prospective study of 1580 Japanese individuals who participated in an annual health check-up in 2014 with 2.8 years of follow-up. All participants had free triiodothyronine (T3) and free thyroxine (T4) levels in the normal range. Among study participants, 88 were diagnosed as having SCH. Even though no significant correlation was observed between HbA1c and annual change in estimated GFR among participants without SCH (multi-adjusted standardized parameter estimate (β) = 0.03, p = 0.250), a significant inverse association was observed among participants with SCH (β = −0.26, p = 0.014). When those analyses were performed among participants who were not taking glucose lowering medication, the observed associations were essentially the same: β = 0.03, p = 0.266 for participants without SCH and β = −0.32, p = 0.006 for participants with SCH, respectively. Therefore, SCH status could influence the association between HbA1c and renal function.

Lipid profile in mild subclinical hypothyroidism: systematic review and meta-analysis

INTRODUCTION

Only severe subclinical hypothyroidism (SSCH) with TSH above 10 mIU/L is considered a risk factor of hyperlipidemia and cardiovascular disease. The results of published papers on mild subclinical hypothyroidism (MSCH) with TSH below10 mIU/L are contradictory. The objective of the study was to conduct a systematic review and meta-analysis on lipid profiles in a population of patients with MSCH (TSH10> mIU/L and normal T3, T4) in comparison with euthyroid subjects.

EVIDENCE ACQUISITION

The electronic databases PubMed, CIANHL, Scopus, and Web of Science were searched systematically between August 20, 2018 and September 15, 2018, without limitation on the date of publication or the language. Titles, abstracts and articles were reviewed to identify papers that evaluated lipid profiles in patients with MSCH compared to euthyroid.

EVIDENCE SYNTHESIS

A systematic review of the studies and a meta-analysis using R software (version 3.6.1) were performed. Thirty-five case control and cohort studies were included in the meta-analysis. Total cholesterol (TC), low density lipoprotein (LDL), and triglycerides (TG) were significantly higher and high-density lipoprotein (HDL) was significantly lower in MSCH patients compared to euthyroid individuals. Mean differences (MD) [95% CI] were 12.75 [6.02, 19.48], 10.95 [6.37, 15.54], 19.27 [10.90, 27.64], and -1.81 [-3.38, -0.23], respectively. No significant difference was observed for very low-density lipoproteins (VLDL), apolipoprotein A1 (apoA1), or apolipoprotein B (apoB). The studies were of fair to good quality.

CONCLUSIONS

MSCH is associated with an increase in major atherogenic lipoproteins and should be viewed as a cardiovascular risk factor.

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.

Infliximab ameliorates tumor necrosis factor-alpha exacerbated renal insulin resistance induced in rats by regulating insulin signaling pathway

Infliximab (IFX), a monoclonal antibody for tumor necrosis factor-alpha (TNF-α), is known to restore blood glucose homeostasis. However, its effects on improving renal insulin resistance (IR) are not yet studied. So we investigate the impact of infliximab on renal insulin signaling pathway in IR rat model regarding to metformin (MET). The induced IR was confirmed by a high oral glucose tolerance test, an elevation of lipid profile and the homeostatic model assessment of insulin resistance 2 (HOMA-IR 2) values. Subsequently, IR rats were concurrently treated with either MET (100 mg/kg/day) or IFX (one dose 5 mg/kg) besides IR and normal control (NC) groups. Four weeks later, IR control rats displayed hyperglycemia, hyperinsulinemia and elevation in HOMA-IR 2, renal function markers and renal tissue TNF-α, interleukins-1β and 6 (Il-1β, IL-6) and suppressor of cytokines signaling 3 (SOCS3) contents as well as glomerulosclerosis when compared to NC group. Additionally, the phosphorylation of renal insulin receptor substrate 1 (IRS1), phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) were markedly impaired. Treatment with either MET or IFX significantly improved IR and kidney functions. The effects of the drugs were achieved by the downregulation of renal inflammatory cytokines and SOCS3 levels and the amelioration of the renal IRS1/PI3K/Akt pathway. In conclusion, MET and IFX ameliorated the TNF-α worsening effect on IR in rat renal tissues by regulating insulin signaling. Interestingly, infliximab was superior to metformin in regulating insulin signaling pathway. Therefore, infliximab could be used as an adjuvant therapy in improving renal IR.

Metabolic profile and prolactin serum levels in men with type 2 diabetes mellitus: Old-new rubric

Background:

Prolactin (PRL) is involved in the regulation of glucose metabolism since high PRL serum levels are associated with low incidence of type 2 diabetes mellitus (T2DM). Therefore, the aim of the present study was to assess the metabolic effects of PRL on glucose homeostasis in men with T2DM.

Methods:

Eighty male patients with T2DM compared with 25 male healthy controls matched with patients for age and weight were divided into four groups: Group (A): patients with T2DM on metformin (n = 29), Group (B): patients with T2DM on glyburide (n = 30), Group (C): patients with T2DM on glyburide plus metformin (n = 21), and Group (D): healthy male subjects as control (n = 25). Body mass index (BMI) and blood pressure measurements were determined. Fasting blood glucose (FBG), glycated hemoglobin, total cholesterol, triglyceride (TG), high-density lipoprotein, low-density lipoprotein, atherogenic index, fasting serum insulin, insulin resistance (IR), and β-cell function of the pancreas were determined by homeostatic model assessment-2 (HOMA-IR). Furthermore, C-reactive protein and PRL serum level were determined in patients with T2DM and healthy control men.

Results:

BMI of T2DM patients was higher as compared with control (P = 0.003). Combination therapy (glyburide plus metformin) in patients with T2DM showed better effect on most of glycemic indices and lipid profile than glyburide or metformin monotherapy (P < 0.05). PRL serum level was higher in patients with T2DM as compared with control (P = 0.001). PRL serum level was high in glyburide-treated patients as compared with metformin-treated patients (P = 0.002).

Conclusion:

This study concludes that elevated PRL serum level in patients with T2DM is associated with diabetic complications. Diabetic pharmacotherapy mainly metformin reduced PRL serum level in patients with T2DM through amelioration of IR.

Study of Vitamin D Level and Vitamin D Receptor Polymorphism in Hypothyroid Egyptian Patients

Purpose

The current study aimed at assessing vitamin D level and vitamin D receptor polymorphism in hypothyroid Egyptian patients and its effect on hypothyroidism and thyroid morphology, also to find a causal relation between vitamin D and hypothyroidism.

Methods

This case-control study was conducted on 35 hypothyroid patients and 35 matched unrelated healthy controls. Total serum 25-hydroxyvitamin D3 and thyroid antibodies were measured using a human ELISA kit. Genotyping was performed by using real-time PCR. HOMA-IR was also calculated (fasting insulin in mIU/L × fasting glucose in mg/dL/405). All subjects were assessed for thyroid morphology by thyroid ultrasonography.

Results

Vitamin D level was lower in hypothyroid patients than in control subjects. Vitamin D was also inversely related to TSH, HOMA-IR, and levels of anti-TG and anti-TPO. VDR polymorphism (Fok1 and Apa1) had no relation to TSH or vitamin D levels in both patients and control groups. Low vitamin D levels were associated with increased thyroid vascularity and nodularity; furthermore, vitamin D was inversely proportional to thyroid gland volume. Correlation of HOMA-IR with the levels of both anti-TG and anti-TPO in the 70 subjects proved that HOMA-IR was positively correlated to both antibodies.

Conclusion

This study confirmed the association of vitamin D deficiency with hypothyroidism, thyroid autoimmunity, increased volume, nodularity, and vascularity of thyroid gland in hypothyroid patients as well as increased HOMA-IR. It proved the association between HOMA-IR and thyroid autoimmunity. The study proved no association between VDR polymorphisms (Fok1 and Apa1) with either vitamin D levels or TSH levels.

Exercise training-induced changes in metabolic syndrome parameters, carotid wall thickness, and thyroid function in middle-aged women with subclinical hypothyroidism

This study analyzed the differences in effects of a 12-week combination of exercise training program with resistance training and aerobic exercises on the risk factors of metabolic syndrome, carotid wall thickness, and thyroid function, between subclinical hypothyroidism patients and obese groups, in middle-aged women. Subjects consisted of either 20 middle-aged women in the subclinical hypothyroidism (SCH) group or 20 obese (body mass indices [BMI], ≥ 25 kg/m²) women without hypothyroidism in the obese (OB) group. The body composition, blood lipid factors, hormones associated with thyroid functions, blood pressure (BP), and carotid intima-media thickness were measured, while physical fitness was ascertained. In the SCH group, waist circumference (WC) and high-density lipoprotein cholesterol values were outside the normal ranges, while WC and systolic BP (SBP) were outside the normal ranges in the OB group. Following the 12-week training program, significantly positive changes occurred in body fat percentage, sit and reach test results, and SBP (p < 0.05) in the SCH group, while in the OB group, significantly positive changes in BMI, WC, sit and reach test results, SBP, and diastolic BP (DBP, p < 0.05) were observed. In addition, both groups showed significant decreases in intima-media thickness of the right carotid bifurcation (p < 0.05). However, in the two groups, the 12-week exercise training program did not have similar significant impact on the hormones related to thyroid functions and blood lipids. Therefore, further research on exercise training that can effectively induce changes in the hormones associated with thyroid functions in patients with subclinical hypothyroidism is necessary.

Effects of diabetic pharmacotherapy on prolactin hormone in patients with type 2 diabetes mellitus: Bane or Boon

Prolactin is a polypeptide hormone secreted from the anterior part of the pituitary gland which was implicated as a diabetogenic factor in the pathogenesis of type 2 diabetes mellitus (T2DM). Therefore, the aim of the present study was to evaluate prolactin serum levels in patients with T2DM regarding the effect of diabetic pharmacotherapy. Eighty patients with T2DM compared with 25 male healthy controls were recruited and divided into four groups: Group I - 29 patients with T2DM treated with metformin, Group II - 30 patients with T2DM treated with glyburide, Group III - 21 patients with T2DM treated with glyburide plus metformin, and Group IV - 25 control male healthy patients. Prolactin serum levels were high in patients with T2DM compared with controls (P < 0.01). Prolactin serum levels were higher in glyburide-treated patients compared with metformin-treated patients (P < 0.01). This study concludes that high prolactin levels in patients with T2DM are linked with diabetic complications and regarded as a beneficial phenomena to overcome IR and diabetic complications. Metformin but not glyburide reduced prolactin levels due to the improvement of insulin resistance.