TSH-lowering effect of metformin in type 2 diabetic patients: differences between euthyroid, untreated hypothyroid, and euthyroid on L-T4 therapy patients

Impaired sensitivity to thyroid hormones is associated with different grades of hypertension: A multicenter cross-sectional study

BACKGROUND AND AIM

Accumulating evidence suggests a potential link between thyroid function with hypertension. However, the research results are limited, and there is no research to explore the relationship between central and peripheral thyroid hormones (THs) sensitivity and different grades of hypertension in patients with coronary heart disease (CHD). This study aims to prove the complex interaction between thyroid system and blood pressure, and provides new ideas for the assessment of hypertension in patients with CHD.

METHODS AND RESULTS

Calculate parameters representing central and peripheral sensitivity to THs. Logistic regression analysis was used to analyze the relationship between central and peripheral THs sensitivity of CHD patients and different grades of hypertension, especially in different ages, sexes, blood glucose levels, smoking, and drinking statuses. Among the 34,310 participants, 19,610 (57.16 %) were diagnosed with hypertension. The risk of hypertension and TSHI (OR: 0.88; 95 % CI: 0.87-0.90; P < 0.001), TT4RI (OR: 0.998; 95 % CI: 0.998-0.999; P < 0.001), TFQI (OR: 0.63; 95 % CI: 0.60-0.67; P < 0.001), PTFQI (OR: 0.63; 95 % CI: 0.59-0.67; P < 0.001) was negatively associated. The risk of hypertension was positively associated with FT3/FT4 (OR: 1.20; 95 % CI: 1.17-1.22; P < 0.001). After stratified analysis, these associations remained significant at different ages, sexes, blood glucose levels, grades of hypertension, smoking, and drinking statuses (P < 0.001).

CONCLUSIONS

This study shows that the decrease in central THs sensitivity index and the increase in peripheral THs sensitivity index are associated with a higher risk of hypertension in CHD patients.

Association of thyroid hormone sensitivity index with stroke in patients with coronary artery disease

BACKGROUND AND AIMS

Thyroid hormones (THs) will affect the occurrence and prognosis of stroke, and the research on THs sensitivity index and stroke in patients with coronary heart disease (CHD) is scarce. The goal of this study is to look into the relationship between central and peripheral THs sensitivity index and stroke in patients with CHD.

METHODS

Between January 1, 2014, and September 30, 2020, 30,160 patients with CHD were enrolled in this study. By computing the thyroid feedback quantile index (TFQI), thyroid stimulating hormone index (TSHI), and thyrotropin thyroxine resistance index (TT4RI), the central sensitivity indexes to THs was assessed, and the ratio of serum free triiodothyronine (FT3) to serum free thyroxine (FT4) was used to assess peripheral THs sensitivity. The relationship between central and peripheral THs sensitivity index and stroke was investigated using logistic regression, especially in different types of stroke, ages, sexes, and blood glucose levels.

RESULTS

Stroke risk is positive associated with TSHI, TFQI, and PTFQI. In subgroup analysis, the OR values of these relationships are higher in people younger than 65 years old, male, and diagnosed with diabetes. In addition, stroke risk was negatively associated with FT3/FT4, and the OR values of these relationships were lower in people older than 65 years, female, and diagnosed with prediabetes.

CONCLUSIONS

This study demonstrates that the increase in the central THs sensitivity index and the decrease in the peripheral THs sensitivity index are associated with a higher risk of stroke in CHD patients, and provides new ideas for the assessment of stroke in patients with CHD.

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.

The effect of metformin therapy on serum thyrotropin and free thyroxine concentrations in patients with type 2 diabetes: a meta-analysis

Type 2 diabetes and thyroid function disorders are two common chronic endocrine disorders with the high prevalence in various populations. Metformin is well established as the first-line drug therapy for managing diabetes mellitus. In this meta-analysis, we aimed to determine the effect of metformin on serum TSH and FT4 concentrations in patients with type 2 diabetes. We searched PubMed, Scopus, web of science, Cochrane library, and google scholar to collect information on the effect of metformin on serum TSH and FT4 levels. Demographic and clinical information and serum TSH and FT4 concentrations before and after metformin treatment were extracted. Studies on patients over 18 years of age were included. A total of 11 studies including 1147 patients were selected for the final analysis. In hypothyroid patients, the TSH level decreased significantly after treatment with metformin (Hedges's g:1.55, 95%CI 0.93-2.16, p-value < 0.001); FT4 level increased slightly after taking metformin, but the increase was not significant (Heddges's g: - 0.30, 95%CI  - 0.90,0.31, p-value = 0.34). In euthyroid subjects, the slight decrease found in TSH and FT4 concentrations was not statistically significant. Metformin reduces TSH levels in hypothyroid patients; however, it has no effect on TSH levels in euthyroid patients. Metformin does not affect serum FT4 levels in euthyroid and hypothyroid patients.

Association Between Thyroid Parameters and Subclinical Atherosclerosis in Hospitalised Euthyroid Patients with Type 2 Diabetes Mellitus

Purpose

To explore the association between thyroid parameters and subclinical atherosclerosis (AS) in hospitalised euthyroid patients with type 2 diabetes mellitus (T2DM).

Patients and Methods

A retrospective analysis was conducted involving 1245 inpatients with T2DM. Free triiodothyronine (FT3), free thyroxine (FT4), and thyroid stimulating hormone (TSH) levels were measured, and carotid artery ultrasonography was performed. Thyroid hormone (TH) sensitivity was evaluated using thyroid feedback quantile-based index (TFQI), TSH index (TSHI), thyrotropin thyroxine resistance index (TT4RI), and free triiodothyronine/free thyroxine ratio (FT3/FT4).

Results

In inpatients with T2DM having normal thyroid function, the incidence of subclinical AS declined with increasing levels of FT3, FT4, and FT3/FT4 (P trend < 0.05). Logistic regression analysis revealed that FT4 (OR, 0.914; 95% CI, 0.845-0.989), FT3 (OR, 0.374; 95% CI, 0.277-0.504), and FT3/FT4 (OR, 0.036; 95% CI, 0.013-0.061) were independently associated with subclinical AS (P < 0.05). However, TSH, TFQI, TSHI, and TT4RI levels were not associated with subclinical AS (P > 0.05). FT3/FT4 demonstrated superior predictive accuracy for subclinical AS than that of FT3 or FT4 alone (P < 0.001), with a cutoff point of 0.25.

Conclusion

In euthyroid inpatients with T2DM, subclinical AS exhibited negative correlation with FT3, FT4, and FT3/FT4 levels, independent of other risk factors for AS. Additionally, FT3/FT4 ratio had a good predictive value for subclinical AS.

Medications and Food Interfering with the Bioavailability of Levothyroxine: A Systematic Review

Purpose

Levothyroxine is a common prescribed drug. Many medications and food, however, can interfere with its bioavailability. The aim of this review was to summarize the medications, food and beverages that interact with levothyroxine and to assess their effects, mechanisms and treatments.

Methods

A systematic review on interfering substances that interact with levothyroxine was performed. Web of Science, Embase, PubMed, the Cochrane library, grey literature from other sources and the lists of references were searched for human studies comparing the levothyroxine efficacy with and without interfering substances. The patient characteristics, drug classes, effects and mechanism were extracted. The NHLBI study quality assessment tools and the JBI critical appraisal checklist were used to assess the quality of included studies.

Results

A total of 107 articles with 128 studies were included. Drugs interactions were revealed in calcium and iron supplements, proton pump inhibitors, bile acid sequestrants, phosphate binders, sex hormones, anticonvulsants and other drugs. Some food and beverage could also induce malabsorption. Proposed mechanisms included direct complexing, alkalization, alteration of serum thyroxine-binding globulin levels and acceleration of levothyroxine catabolism via deiodination. Dose adjustment, administration separation and discontinuation of interfering substances can eliminate the interactions. Liquid solutions and soft-gel capsules could eliminate the malabsorption due to chelation and alkalization. The qualities of most included studies were moderate.

Conclusion

Lots of medications and food can impair the bioavailability of levothyroxine. Clinicians, patients and pharmaceutical companies should be aware of the possible interactions. Further well-designed studies are needed to provide more solid evidence on treatment and mechanisms.

Sensitivity to thyroid hormone indices are associated with papillary thyroid carcinoma in Chinese patients with thyroid nodules

BACKGROUND

The association between thyroid hormone sensitivity and thyroid cancer is unknown, and we aimed to investigate the association between sensitivity to thyroid hormone indices and papillary thyroid carcinoma (PTC) in Chinese patients with thyroid nodules (TNs).

METHODS

A total of 1,998 patients undergoing thyroid surgery due to TNs from Nanjing Drum Tower Hospital were included in this study. We evaluated central sensitivity to thyroid hormones, such as thyroid stimulating hormone index (TSHI), TSH T4 resistance index (TT4RI), thyroid feedback quantile-based index (TFQI), and parametric thyroid feedback quantile-based Index (PTFQI). Peripheral sensitivity to thyroid hormone was evaluated by FT3 to FT4 ratio. Multivariate logistic regression analysis was performed to evaluate the association between sensitivity to thyroid hormone indices and PTC risk.

RESULTS

The results showed that central indices of thyroid hormone sensitivity, including TSHI, TT4RI, TFQI, and PTFQI, were positively associated with PTC risk. For each SD increase in TSHI, TT4RI, TFQI, and PTFQI, the odds ratios (OR, 95% CI) of PTC were 1.31 (1.18-1.46), 1.01 (1.01-1.02), 1.94 (1.45-2.60), and 1.82 (1.41-2.34), respectively. On the other hand, the association between peripheral sensitivity to thyroid hormone and PTC was significantly negative. For each SD increase in FT3/FT4 ratio, the OR (95% CI) of PTC was 0.18 (0.03-0.96), and a negative correlation was found between FT3/FT4 ratio and TNM staging of PTC.

CONCLUSIONS

Sensitivity to thyroid hormone indices could be used as new indicators for predicting PTC in Chinese patients with TNs. Future researches are still needed to confirm our findings.

Association between sensitivity to thyroid hormones and dyslipidemia in patients with coronary heart disease

BACKGROUND

Thyroid hormones affect lipid metabolism via central and peripheral regulation. However, there have been few studies on the association between thyroid hormone sensitivity and dyslipidemia. We aimed to investigate the association between thyroid hormone sensitivity and dyslipidemia in patients with coronary heart disease (CHD).

METHODS

A total of 31,678 patients with CHD were included in this large multicenter retrospective study. Central thyroid hormone sensitivity was evaluated using the thyroid feedback quantile-based index (TFQI), parametric thyroid feedback quantile-based index (PTFQI), thyroid-stimulating hormone index (TSHI), and thyrotropin thyroxine resistance index (TT4RI); peripheral thyroid hormone sensitivity was assessed by the ratio of free triiodothyronine (FT3)/free thyroxine (FT4). Logistic regression analysis was used to analyze the association between thyroid hormone sensitivity and dyslipidemia.

RESULTS

Among 31,678 participants, 21,648 (68.34%) had dyslipidemia. In the multi-adjusted models, the risk of dyslipidemia was positively correlated with TFQI (odds ratio [OR]: 1.04; 95% confidence interval [CI]: 1.03-1.05), PTFQI (OR: 1.09; 95% CI: 1.06-1.12), TSHI (OR: 1.08; 95% CI: 1.06-1.11), and TT4RI (OR: 1.08; 95% CI: 1.05-1.11). Conversely, the risk of dyslipidemia was negatively correlated with FT3/FT4 (OR: 0.94; 95% CI: 0.92-0.97). In stratified analyses, the association between thyroid hormone sensitivity and dyslipidemia was statistically significant for different sexes, glucose levels, and blood pressure states.

CONCLUSION

There is a significant association between sensitivity to thyroid hormones and dyslipidemia, regardless of sex, glucose level, or blood pressure. Graphical abstract.

Thyroid Dysfunction and Cardiovascular Events in Patients With Dysglycemia

OBJECTIVES

Subclinical thyroid disease is the most common form of thyroid dysfunction and may be associated with adverse cardiovascular outcomes in people at high risk for cardiovascular events. Our objective in this study was to assess the association of thyroid function and thyroid hormone replacement with cardiovascular outcomes in high-risk individuals with dysglycemia and additional cardiovascular risk factors.

METHODS

The relationship between baseline thyrotropin (TSH) level and incidence of the composite outcome of nonfatal myocardial infarction, nonfatal stroke or cardiovascular death; an expanded composite of this outcome plus revascularization or hospitalization for heart failure; and mortality was assessed in 8,401 ORIGIN trial participants with a baseline measurement of TSH. The hazard of each outcome according to either baseline levothyroxine use or TSH-defined hyperthyroidism, euthyroidism, subclinical hypothyroidism and overt hypothyroidism was estimated before and after adjustment for baseline demographic and clinical characteristics and treatment allocation.

RESULTS

Of all participants, 91.5% were euthyroid, 0.8% were hyperthyroid, 5.5% had subclinical hypothyroidism and 2.2% had overt hypothyroidism. Subclinical hypothyroidism predicted both the expanded cardiovascular outcome (hazard ratio [HR]=1.24, 95% confidence interval [CI] 1.06 to 1.46) and mortality (HR=1.37, 95% CI 1.12 to 1.67), whereas levothyroxine use predicted fewer deaths (HR=0.72, 95% CI 0.56 to 0.94).

CONCLUSION

Subclinical hypothyroidism predicts future cardiovascular events and mortality in people with dysglycemia and other cardiovascular risk factors.

Metformin Attenuates Inflammation and Fibrosis in Thyroid-Associated Ophthalmopathy

The pathogenesis of thyroid-associated ophthalmopathy (TAO) is still unclear, and therapeutic drugs have great limitations. As metformin has multiple therapeutic effects in many autoimmune diseases, we explored the effects of metformin on TAO in an in vitro fibroblast model. We used orbital connective tissues and fibroblasts that were obtained from TAO patients and normal controls. The activity of adenosine monophosphate-activated protein kinase (AMPK) and the levels of inflammatory or fibrotic factors were examined by immunofluorescence (IF) and immunohistochemistry (IHC). Quantitative real-time polymerase chain reaction (qPCR), cytokine quantification by enzyme-linked immunosorbent sssay (ELISA), IF, and western blotting (WB) were used to measure the expression of factors related to inflammation, fibrosis, and autophagy. To determine the anti-inflammatory and antifibrotic mechanisms of metformin, we pretreated cells with metformin, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR, an AMPK activator) or compound C (CC, an AMPK inhibitor) for 24 h and used WB to verify the changes in protein levels in the AMPK/mammalian target of rapamycin (mTOR) pathway. We determined that the low activity of AMPK in the periorbital tissue of TAO patients may be closely related to the occurrence and development of inflammation and fibrosis, and metformin exerts multiple effects by activating AMPK in TAO. Furthermore, we suggest that AMPK may be a potential target of TAO therapy.

Rosuvastatin potentiates the thyrotropin-lowering effect of metformin in men with non-autoimmune subclinical hypothyroidism and prediabetes

WHAT IS KNOWN AND OBJECTIVE

Metformin treatment decreases thyrotropin levels in individuals with hypothyroidism and this effect seems to be mediated by the 5'-adenosine monophosphate-activated protein kinase pathway in the pituitary. The activity of this pathway is also stimulated by statins. The current study was aimed at investigating whether the impact of metformin on hypothalamic-pituitary-thyroid axis activity is affected by statin use.

METHODS

The study included three matched groups of men with non-autoimmune hypothyroidism and prediabetes: patients treated for at least 6 months with high-intensity rosuvastatin therapy (20-40 mg daily) [groups A (n = 24) and C (n = 19)] and men not receiving statin therapy [group B (n = 24)]. Over the entire study period (6 months), groups A and B received metformin (2.55-3 g daily). Moreover, groups A and C continued rosuvastatin therapy. The lipid profile, glucose homeostasis markers, and plasma concentrations of thyrotropin, total and free thyroid hormones, prolactin, FSH, LH, ACTH and insulin-like growth factor-1 were determined at baseline and 6 months later.

RESULTS AND DISCUSSION

Fifty-nine patients completed the study. There were differences between groups A and C and group B in baseline values of total cholesterol, LDL-cholesterol, gonadotropins and ACTH. Although observed in both groups of metformin-treated patients, the effect on thyrotropin levels was more pronounced in group A than in group B. The impact on fasting glucose and insulin sensitivity was stronger in group B than group A. In turn, only in group A metformin tended to reduce gonadotropin levels. There were no differences between follow-up and baseline values of lipids, total and free thyroid hormones, prolactin, ACTH and insulin-like growth factor-1 in both these groups. In group C, all assessed variables remained at a similar level.

WHAT IS NEW AND CONCLUSION

The results of the current study suggest that rosuvastatin potentiates the inhibitory effect of metformin on thyrotrope secretory function.

Effects of Slow-Acting Metformin Treatment on the Hormonal and Morphological Thyroid Profile in Patients with Insulin Resistance

Metformin appears to reduce TSH levels in untreated hypothyroid patients. In contrast, in euthyroid patients with type 2 diabetes mellitus (T2DM), metformin is initially devoid of effects on TSH. However, it is followed by a significant reduction in TSH level after twelve months of treatment. Additionally, some evidence suggests that metformin may also improve thyroid morphological abnormalities. This study aimed to evaluate the effects of metformin not only on TSH and thyroid hormone values, but also on thyroid volume and nodules. A total of 50 patients (mean age: 36.9 ± 12.8 years) with insulin resistance (homeostatic model assessment (HOMA) index ≥2.5) and with thyroid uninodular disease were recruited for this study. They were prescribed slow-acting metformin at a daily dose of 500 mg for six months. Treatment with metformin in euthyroid patients with uninodular thyroid disease and insulin resistance reduces TSH levels, increases FT4 and FT3 values, and decreases thyroid and nodule volumes. These data suggest that metformin may be an effective drug not only for the treatment of T2DM and metabolic syndrome, but also for thyroid disease.

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.

Metformin in the Treatment of Amisulpride-Induced Hyperprolactinemia: A Clinical Trial

Objective

To evaluate the efficacy and safety of metformin in the treatment of amisulpride-induced hyperprolactinemia.

Methods

A total of 86 schizophrenic patients who developed hyperprolactinemia after taking amisulpride were screened and randomly assigned to the metformin group (42 patients) and placebo group (44 patients) and followed up for eight weeks. The patients’ serum prolactin levels, blood glucose and lipids were measured at the baseline and the end of the intervention. The treatment emergent symptom scale (TESS) was also assessed.

Results

After eight weeks of intervention, serum prolactin levels in the metformin group decreased from (1737.360 ± 626.918) mIU/L at baseline to (1618.625 ± 640.865) mIU/L, whereas serum prolactin levels in the placebo group increased from (2676.470 ± 1269.234) mIU/L at baseline to (2860.933 ± 1317.376) mIU/L. There was a significant difference in prolactin changes (F^covariance = 9.982, P = 0.002) between the two groups. There was no significant difference in the incidence of adverse drug reactions (P > 0.05) between the two groups.

Conclusion

Metformin is able to improve amisulpride-induced hyperprolactinemia with its safety.

Spectrum of thyroid function test among type 2 diabetic patients attending a rural health facility, southwest Nigeria: A hospital-based study

Objectives:

The thyroid gland produces hormones that have significant influence on carbohydrate metabolism; its disorders may affect carbohydrate metabolism in type 2 diabetic patients (T2DM) more than the non-diabetic (NDM) patients as reported in various studies. We determined the spectrum of thyroid function tests (TFTs) profile among T2DM in our rural health facility.

Methods:

T2DM patients and NDM patients were recruited for the study. The age, educational level, occupation, marital status, and duration of diabetes were extracted from interviewer’s administered questionnaire. The weight, height, body mass indices (BMIs), and the waist and hip circumferences were measured. Waist-hip ratios (WHR) were calculated for all participants. Venous blood was collected and assayed for free triiodothyronine (fT3), free thyroxine (fT4), and thyroid stimulating hormone (TSH) using a Chemiluminescence Immunoassay (CLIA) 2nd Generation Autoanalyzer. The mean, standard deviation, frequencies, and percentages were calculated for the variables. The student’s t-test and chi-square test were also determined as appropriate.

Results:

Seventy-eight patients made up of 56 T2DM and 22 NDM were evaluated in this study. Fifty-one were males while 27 were females; 67.9% and 59.1% of the female participants were T2DM and NDM, respectively. The WHR was significantly higher in T2DM than NDM (0.92 ± 0.05 versus 0.88 ± 0.06). The TSH was higher in T2DM than the NDM. Forty-four (78.6%) of the T2DM had euthyroid (normal) biochemical pattern; 12 (21.4%) showed abnormal biochemical pattern of euthyroid sick syndrome, subclinical hyperthyroid, and subclinical hypothyroid. Thirty (53.6%) of the T2DM were diagnosed less than five years ago. The value of TSH was increasing with the duration of diabetes but not in a statistically significant way. None of the T2DM showed overt hypothyroid or hyperthyroid test result.

Conclusion:

Thyroid function test may identify diabetics with altered thyroid hormone status that may impact on their metabolic control. Knowledge of the functional state of the thyroid gland can help in achieving a better metabolic control and attenuate the development of complications in T2DM.

Links between Thyroid Disorders and Glucose Homeostasis

Thyroid disorders and diabetes mellitus often coexist and are closely related. Several studies have shown a higher prevalence of thyroid disorders in patients with diabetes mellitus and vice versa. Thyroid hormone affects glucose homeostasis by impacting pancreatic β-cell development and glucose metabolism through several organs such as the liver, gastrointestinal tract, pancreas, adipose tissue, skeletal muscles, and the central nervous system. The present review discusses the effect of thyroid hormone on glucose homeostasis. We also review the relationship between thyroid disease and diabetes mellitus: type 1, type 2, and gestational diabetes, as well as guidelines for screening thyroid function with each disorder. Finally, we provide an overview of the effects of antidiabetic drugs on thyroid hormone and thyroid disorders.

Impaired Sensitivity to Thyroid Hormones Is Associated With Elevated Blood Glucose in Coronary Heart Disease

CONTEXT

Thyroid hormones influence glucose homeostasis through central and peripheral regulation. To date, the association between thyroid hormone sensitivity and elevated blood glucose (EBG) in patients with coronary heart disease (CHD) remains unknown. The purpose of this study was to investigate the association between thyroid hormone sensitivity and risk of EBG in patients with CHD, and to further explore their association in different sexes and ages.

METHODS

This large multicenter retrospective study included 30,244 patients with CHD (aged 30-80 years) between 1 January 2014 and 30 September 2020. Parameters representing central and peripheral sensitivity to thyroid hormones were calculated. Central sensitivity to thyroid hormones was assessed by calculating the Thyroid Feedback Quantile-based Index (TFQI), Thyroid-stimulating Hormone Index (TSHI), and Thyrotropin Thyroxine Resistance Index (TT4RI), and Parametric Thyroid Feedback Quantile-based Index (PTFQI); peripheral sensitivity to thyroid hormones was evaluated using the ratio of free triiodothyronine (FT3) /free thyroxine (FT4). Taking normal glucose tolerance (NGT) as a reference, logistic regression was used to analyse the relationship between central and peripheral thyroid hormone sensitivity and EBG in patients with CHD.

RESULTS

Among the 30,244 participants, 15,493 (51.23%) had EBG. The risk of EBG was negatively correlated with TSHI (OR: 0.91; 95%CI: 0.91 to 0.92; P < 0.001), TT4RI (OR: 0.99; 95% CI: 0.99 to 0.99; P<0.001), TFQI (OR: 0.82; 95%CI: 0.80 to 0.84; P <0.001) and PTFQI (OR: 0.76; 95%CI: 0.74 to 0.78; P<0.001). Compared to males and patients aged 60 and below, the OR value for EBG was lower in females and in patients aged over 60 years old. Conversely, EBG risk was positively associated with FT3/FT4 (OR: 1.08; 95% CI: 1.07 to 1.09; P <0.001) and in the sex-categorized subgroups, males had higher OR values than females.

CONCLUSIONS

This study showed that thyroid hormone sensitivity is significantly associated with EBG in patients with CHD. This association is higher in females than in males, and the association in those aged over 60 years old is higher than that in patients aged 60 years and below.

Impaired sensitivity to thyroid hormones and carotid plaque in patients with coronary heart disease: A RCSCD-TCM study in China

CONTEXT

Previous studies on the association between thyroid function and carotid plaque have shown contradictory results, which may be attributable to the sensitivity to thyroid hormone indices. This study aimed to analyze the association between thyroid hormone sensitivity and risk of carotid plaque in patients with coronary heart disease (CHD) and further explore this association according to sex, age, smoking, and drinking status.

METHODS

This large-scale, multi-center, retrospective, cross-sectional study included 6679 patients with CHD (age 35-75). Central sensitivity to thyroid hormone was evaluated by the thyroid feedback quantile-based index (TFQI), parametric thyroid feedback quantile-based index (PTFQI), thyroid-stimulating hormone index (TSHI), and thyrotroph thyroxine resistance index (TT4RI). Peripheral sensitivity to thyroid hormone was assessed by free triiodothyronine/free thyroxine (FT3/FT4) ratio. Taking no carotid plaque as a reference, this study used logistic regression to analyze the association between central and peripheral thyroid hormone sensitivity and carotid plaque in patients with CHD.

RESULTS

Of the 6679 patients with CHD, 4843 (72.50%) had carotid plaque. In the multi-adjusted models, the TFQI (odds ratio [OR]: 1.50; 95% confidence interval [CI]: 1.26-1.78; P < 0.001), PTFQI (OR: 1.76; 95% CI: 1.46-2.12; P < 0.001), TSHI (OR: 1.21; 95% CI: 1.10-1.33; P < 0.001), and TT4RI (OR: 1.00; 95% CI: 1.00-1.01; P = 0.003) were positively associated with the risk of carotid plaque. Compared with that in females and people > 60 years, the OR value for carotid plaque was higher in males and people ≤ 60 years. Similarly, smokers and drinkers had higher OR values for carotid plaque than non-smokers and non-drinkers. Conversely, FT3/FT4 ratio (OR: 0.75; 95% CI: 0.70-0.81; P < 0.001) was negatively associated with carotid plaque, and the OR value for carotid plaque was lower in males, patients ≤ 60 years, smokers, and drinkers.

CONCLUSION

This study showed that thyroid hormone sensitivity is significantly associated with carotid plaque in patients with CHD. This association is more significant in males, patients ≤ 60 years, smokers, and drinkers.

The impact of metformin on hypothalamic-pituitary-thyroid axis activity in postmenopausal women with untreated non-autoimmune subclinical hypothyroidism

Metformin was found to reduce elevated thyrotropin levels in subjects with hypothyroidism. The impact on thyrotropin levels was stronger in women receiving oral contraceptive pills than in women not using any contraception. The aim of the present study was to determine whether physiological levels of oestradiol determine the effect of metformin on hypothalamic-pituitary-thyroid axis activity. The study population included 40 postmenopausal women with prediabetes and untreated non-autoimmune subclinical hypothyroidism, using (group A; n = 18) or not using (group B; n = 22) oestradiol replacement therapy. Over the entire study periods, all subjects were treated with metformin (2.55-3.00 g daily). Plasma levels of glucose, lipids, insulin, thyrotropin, free thyroxine, free triiodothyronine, prolactin, gonadotropins and oestradiol were measured, while the structure parameters of thyroid homeostasis and the degree of insulin sensitivity were calculated at the beginning of the study and 6 months later. At entry, both groups differed in gonadotropin and oestrogen levels. Despite improving insulin sensitivity, thyrotropin levels and Jostel's thyrotropin index in both study groups, these effects were stronger in group A than group B. Only in group A, metformin increased SPINA-GT, while only in group B the drug decreased FSH levels. Levels of the other variables remained at a similar level throughout the study. The effect of treatment on thyrotropin levels correlated with its baseline values, as well as with the improvement of insulin sensitivity. The results obtained suggest that the impact of metformin on hypothalamic-pituitary-thyroid axis activity depends on the oestrogen status of patients.

A breakthrough-like effect of metformin reduces peripheral resistance to triiodothyronine in euthyroid, non-insulin-resistant, type 2 diabetic patients

BACKGROUND

Type 2 diabetes is characterized, beyond the insulin resistance, by polyhormonal resistance. Thyroid hormonal resistance has not yet been described in this population of patients. Metformin is used to decrease insulin resistance, and at present, it is assumed to influence the effect of triiodothyronine, as well.

METHODS

In this open-label, pilot, hypothesis-generating, follow-up study, 21 patients were included; all of them were euthyroid with drug naïve, newly diagnosed type 2 diabetes. Before and after 4 weeks of metformin therapy, fructosamine, homeostasis model assessment for insulin resistance (HOMA-IR), thyroid hormones, T3/T4 ratio, and TSH, as well as blood pressure and heart rate using ambulatory blood pressure monitor were measured. We also conducted an in vitro study to investigate the possible mechanisms of T3 resistance, assessing T3-induced Akt phosphorylation among normal (5 mM) and high (25 mM) glucose levels with or without metformin treatment in a human embryonal kidney cell line.

RESULTS

Metformin decreased the level of T3 (P < 0.001), the ratio of T3/T4 (P = 0.038), fructosamine (P = 0.008) and HOMA-IR (P = 0.022). All these changes were accompanied by an unchanged TSH, T4, triglyceride, plasma glucose, bodyweight, blood pressure, and heart rate. In our in vitro study, T3-induced Akt phosphorylation decreased in cells grown in 25 mM glucose medium compared to those in 5 mM. Metformin could not reverse this effect.

CONCLUSION

Metformin seems to improve T3 sensitivity in the cardiovascular system in euthyroid, type 2 diabetic patients, the mechanism of which may be supracellular.

TSH lowering effects of metformin: a possible mechanism of action

Preliminary clinical evidence suggests that metformin has TSH lowering effects in patients with T2DM and hypothyroidism or in those with TSH serum levels in the upper normal value. Also, metformin may exert a protective role against thyroid nodules growth in patients without insulin-resistance. The cross-talk between tyrosine kinase receptors and the G protein-coupled receptors (which the TSHR belongs to) has been already shown and IRS1 may represent the hub link between TSHR and IR pathways. By influencing IRS1 phosphorylation pattern, metformin may sensitize TSHR to TSH, thus explaining the findings of clinical studies. However, the existence of this molecular pathway must be confirmed through proper studies and further prospective randomized placebo-controlled studies are needed to confirm this hypothesis.

Thyroid disorders in elderly: A comprehensive review

The approach to management of thyroid disorders in the elderly differs from that for younger individuals: it considers frailty of the population, coexisting medical illness and medications, clearance rate of medications and drug-drug interactions along with target organ sensitivity to the treatment. We present a comprehensive review of literature for the clinical presentation, pathophysiology, diagnostic evaluation, and management of thyroid disorders in the elderly.

Exploring the Effect of Metformin to Lower Thyroid-Stimulating Hormone in Euthyroid and Hypothyroid Type-2 Diabetic Patients

Introduction

Metformin is one of the safest, first-line oral hypoglycemic agents used in type-2 diabetes mellitus patients. This study aims to study the effect of metformin on thyroid-stimulating hormone (TSH) in hypothyroid and euthyroid individuals, as both these diseases have an increased prevalence and coexistence.

Method

This hospital-based study was conducted in Jinnah Allama Iqbal Institute of Diabetes and Endocrinology (JAIDE), Allama Iqbal Medical College/Jinnah Hospital Lahore, Pakistan, from October 2019 to April 2020. One hundred and sixty type-2 diabetic participants, aged 25-60 years and meeting the inclusion criteria were enrolled in the study after informed consent. They were divided into two groups, the hypothyroid group who were already on levothyroxine therapy and had a stable TSH in the normal range, and a euthyroid group who had no thyroid dysfunction. Both the groups were started on metformin therapy for the control of type-2 diabetes mellitus and followed for six months. Their blood samples for TSH and free thyroid hormone (fT4) were drawn both prior to and after the study period.

Results

Out of the 160 type-2 diabetic patients, TSH levels showed a significant reduction in the hypothyroid patients (2.33 ± 0.70, p < 0.001) with no significant changes in the euthyroid patients (3.87 ± 0.40, p = 0.206) following six months of metformin therapy. However, there was no significant difference in the fT4 levels in either of the groups.

Conclusion

Metformin has the effect of significantly lowering TSH levels in hypothyroid individuals. However, no such effect was observed in euthyroid patients.

Sensitivity to Thyroid Hormones and Risk of Prediabetes: A Cross-Sectional Study

CONTEXT

Thyroid hormone influences glucose homeostasis through central and peripheral regulations. To date, the link between sensitivity to thyroid hormones and prediabetes remains unknown. We aimed to investigate the association between thyroid hormones sensitivity and risk of prediabetes in both general and euthyroid populations.

METHODS

Participants with serum free triiodothyronine (FT3), free thyroxine (FT4), and thyrotropin (TSH) measurements from the health checkup programs of the First Hospital of China Medical University were collected. We measured the parameters representing central and peripheral sensitivities to thyroid hormones (central sensitivity, assessed by calculating Thyroid Feedback Quantile-based Index (TFQI), TSH Index (TSHI), and Thyrotroph Thyroxine Resistance Index (TT4RI); peripheral sensitivity, evaluated by FT3/FT4 ratio). Associations between thyroid hormones sensitivities and risk of prediabetes were assessed with logistic regression.

RESULTS

A total of 4378 participants (mean age ± SD, 49 ± 11 years) were included, with 1457 (33%) subjects had prediabetes. The risk of prediabetes was negatively associated with levels of TSHI (odds ratio [OR] 0.91; 95% confidence interval [CI], 0.85-0.97), TT4RI (OR 0.91; 95% CI, 0.84-0.99) and Parametric TFQI (PTFQI) (OR 0.89; 95% CI, 0.83-0.95) among all subjects. The association remained significant in euthyroid subjects and euthyroid subjects with negative thyroid autoimmunity. Higher FT3/FT4 ratio was associated with a mild increased risk of prediabetes (95% CI 1.09; 1.02-1.16). Compared with subjects in the lowest quartile of PTFQI, those in the highest quartile had lower risk of prediabetes (0.70; 95% CI, 0.58-0.84).

CONCLUSIONS

Decreased central sensitivity to thyroid hormones is associated with lower risk of prediabetes. This demonstrates the complex interaction between thyroid system and glucose metabolism. Future studies are warranted to confirm our findings and underlying mechanisms.

L-T4 Therapy in the Presence of Pharmacological Interferents

Pharmacological interference on L-thyroxine (L-T4) therapy can be exerted at several levels, namely from the hypothalamus/pituitary through the intestine, where the absorption of exogenous L-T4 takes place. A number of medications interfere with L-T4 therapy, some of them also being the cause of hypothyroidism. The clinician should be aware that some medications simply affect thyroid function tests with no need of modifying the dose of L-T4 that the patient was taking prior to their prescription. Usually, the topic of pharmacological interference on L-T4 therapy addresses the patient with primary hypothyroidism, in whom periodic measurement of serum thyrotropin (TSH) is the biochemical target. However, this minireview also addresses the patient with central hypothyroidism, in whom the biochemical target is serum free thyroxine (FT4). This minireview also addresses two additional topics. One is the costs associated with frequent monitoring of the biochemical target when L-T4 is taken simultaneously with the interfering drug. The second topic is the issue of metabolic/cardiovascular complications associated with undertreated hypothyroidism.

Thyroid scintigraphy in the era of fine-needle aspiration cytology

PURPOSE

To evaluate whether thyroid scintigraphy would alter the clinical management of patients referred for fine-needle aspiration cytology (FNA).

METHODS

We reviewed the medical and imaging records of patients referred to our Department between 2016 and 2019. All the patients had to take a serum thyrotropin test administered in our hospital at least two months before the FNA; where the TSH level was ≤1.5 mIU/L, the patients were subjected to a scan and subsequently to FNA, where indicated. We selected only healthy patients with no previous history of thyroid disease, who were not taking any drugs and who had a TSH level of ≤1.5 mIU/L. We excluded patients with multinodular goitre.

RESULTS

A total of 176 patients were analysed. A total of 67/176 patients (38%) showed a serum of TSH ≤ 0.27 mIU/L. Scintigraphy identified a hot nodule in 142 lesions (80.7%), a warm nodule in 8 lesions (4.5%) and a cold nodule in 26 lesions (14.8%). The ROC curve analysis indicated that a TSH value of ≤0.42 mIU/L identified patients with hyperfunctioning nodules with a sensitivity of 65% and a specificity of 77%. All patients with cold and warm nodules were submitted to FNA: 22/26 (85%) and 5/8 (63%) lesions showed suspected malignancy or were compatible with malignancy, respectively.

CONCLUSION

Speculating on our data, if we had subjected our patients to FNA as indicated by the 2015 ATA guidelines, we would have subjected 117 patients to cytology, from whom 83 had undetected hot nodules. Conversely, by adopting scintigraphy for all patients with TSH ≤ 1.5 mIU/L, 109 patients have avoided FNA. However, our study was performed in a region with a history of mild iodine deficiency. Therefore, we cannot claim that our observation is valid for patients born and living in areas with sufficient iodine uptake. We recommend thyroid scintigraphy for treating single thyroid nodules in euthyroid patients born and living in regions with an iodine deficiency, when TSH levels are below 1.5 mIU/L before FNA.

Metformin: Up to Date

BACKGROUND

Metformin is an oral hypoglycemic agent extensively used as first-line therapy for type 2 diabetes. It improves hyperglycemia by suppressing hepatic glucose production and increasing glucose uptake in muscles. Metformin improves insulin sensitivity and shows a beneficial effect on weight control. Besides its metabolic positive effects, Metformin has direct effects on inflammation and can have immunomodulatory and antineoplastic properties.

AIM

The aim of this narrative review was to summarize the up-to-date evidence from the current literature about the metabolic and non-metabolic effects of Metformin.

METHODS

We reviewed the current literature dealing with different effects and properties of Metformin and current recommendations about the use of this drug. We identified keywords and MeSH terms in Pubmed and the terms Metformin and type 2 diabetes, type 1 diabetes, pregnancy, heart failure, PCOS, etc, were searched, selecting only significant original articles and review in English, in particular of the last five years.

CONCLUSION

Even if many new effective hypoglycemic agents have been launched in the market in the last few years, Metformin would always keep a place in the treatment of type 2 diabetes and its comorbidities because of its multiple positive effects and low cost.

Could Serum TSH Levels Predict Malignancy in Euthyroid Patients Affected by Thyroid Nodules with Indeterminate Cytology?

BACKGROUND

Serum TSH levels in the upper-normal range were reported to be associated with increased risk of thyroid malignancy. However, measurement of TSH levels is currently not recommended for assessing the risk of malignancy in patients with newly diagnosed thyroid nodules.

OBJECTIVE

To evaluate a possible relationship between the serum levels of TSH and the histological outcome of patients undergoing thyroidectomy for thyroid nodules with indeterminate cytology.

MATERIALS AND METHODS

We collected the clinical data of all patients who had performed ultrasound-guided FNA of thyroid nodules with cytological diagnosis of indeterminate lesions (TIR3A and TIR3B) and serum TSH levels within the normal range. All patients had been submitted to thyroid surgery (hemi or thyroidectomy, as appropriate), and histological diagnosis had been performed.

RESULTS

A histological diagnosis of thyroid malignancy was rendered in 74/378 (19.6%) nodules. Patients with histologically proven thyroid malignancy were characterized by higher serum levels of TSH as compared to patients with histologically proven benign nodules (3.03 ± 1.16 vs. 2.37 ± 1.19 mIU/L, p < 0.001). To further analyze the role of serum TSH in predicting thyroid cancer, patients were stratified in 4 groups according to quartiles of TSH concentrations. The prevalence of malignancy was 12.2% for the first quartile and 50.0% for the last quartile. ROC curve analysis identified that a serum TSH level of ≥2.7 mIU/L predicted thyroid malignancy with a sensitivity of 61% and a specificity of 65%.

CONCLUSIONS

TSH levels in the upper-normal range are associated with an increased risk of thyroid malignancy in patients affected by thyroid nodules with indeterminate cytology at FNA. The measurement of serum TSH levels represents an easily performed additional tool for decision-making in patients with indeterminate cytological findings.

Effect of metformin on thyroid function tests in patients with subclinical hypothyroidism: an open-label randomised controlled trial

PURPOSE

Though most of the observational studies have shown that metformin can reduce serum thyroid stimulating hormone (TSH) level in patients of hypothyroidism with diabetes or polycystic ovarian disease, randomised controlled trials are sparse. The primary objective of this study was to evaluate the effect of metformin on thyroid function tests (TSH, free T4, and free T3) in patients with subclinical hypothyroidism (SCH).

METHODOLOGY

In this open label, parallel arm, randomised controlled trial, 60 patients of SCH (TSH 5.5-10 mIU/L) were randomised to either metformin group (1500 mg/day) or control group.

RESULT

A total of 46 patients (23 in each group) completed the study and no significant difference in serum TSH, free T4 or free T3 was found in between the 2 groups. Neither there was any significant change in serum TSH, free T4 or free T3 (pre and post 6 months) within the individual groups. However, the rate of normalisation of serum TSH in patients with negative thyroid antibody was significantly higher than patients with positive thyroid antibody (71.4% vs. 18.8%; P = 0.026) in metformin group in post hoc analysis. Fasting plasma glucose, serum high-density lipoprotein and indices of insulin sensitivity significantly improved in metformin group. Four patients (17%) had mild gastrointestinal adverse effects in the metformin group.

CONCLUSION

We did not find any significant change in thyroid function test in patients with SCH with metformin therapy.

Challenges in Interpreting Thyroid Stimulating Hormone Results in the Diagnosis of Thyroid Dysfunction

The pituitary hormone, thyrotropin (TSH), is regarded as the primary biomarker for evaluating thyroid function and is useful in guiding treatment with levothyroxine for patients with hypothyroidism. The amplified response of TSH to slight changes in thyroid hormone levels provides a large and easily measured signal in the routine care setting. Laboratories provide reference ranges with upper and lower cutoffs for TSH to define normal thyroid function. The upper limit of the range, used to diagnose subclinical (mild) hypothyroidism, is itself a matter for debate, with authoritative guidelines recommending treatment to within the lower half of the range. Concomitant diseases, medications, supplements, age, gender, ethnicity, iodine status, time of day, time of year, autoantibodies, heterophilic antibodies, smoking, and other factors influence the level of TSH, or the performance of current TSH assays. The long-term prognostic implications of small deviations of TSH from the reference range are unclear. Correction of TSH to within the reference range does not always bring thyroid and other biomarkers into range and will not always resolve the patient's symptoms. Overt hypothyroidism requires intervention with levothyroxine. It remains important that physicians managing a patient with symptoms suggestive of thyroid disease consider all of the patient's relevant disease, lifestyle, and other factors before intervening on the basis of a marginally raised TSH level alone. Finally, these limitations of TSH testing mitigate against screening the population for the undoubtedly substantial prevalence of undiagnosed thyroid disease, until appropriately designed randomised trials have quantified the benefits and harms from this approach.

The Impact of Ethinyl Estradiol on Metformin Action on Prolactin Levels in Women with Hyperprolactinemia

Background Metformin reduced prolactin levels only in women with hyperprolactinemia.

Objective The purpose of this case-control study was to compare metformin action on lactoctrope function between women receiving oral contraceptive pills and women not using hormonal contraception.

Methods The study included two groups of matched women with elevated prolactin levels and new-onset prediabetes or diabetes. The first group consisted of 20 women using oral contraceptive pills for at least 12 months before entering the study, while the second group included 20 patients not using any hormonal contraception. Over the whole study period, all women were treated with metformin (1.7–3 g daily). Circulating levels of glucose, insulin, prolactin, thyrotropin, free thyroid hormones, adrenocorticotropic hormone, gonadotropins and insulin-like growth factor-1 were measured at the beginning and at the end of the study (16 weeks later).

Results Thirty-eight patients completed the study. Metformin reduced plasma glucose levels and improved insulin sensitivity but the latter effect was stronger in women receiving oral contraceptive pills than in women not using any contraception. Although metformin treatment decreased plasma prolactin levels in both study groups, this effect was stronger in women taking oral contraceptive pills. Only in this group of women, metformin increased plasma luteinizing hormone levels. The changes in plasma prolactin correlated with their baseline insulin sensitivity and the effect of metformin on insulin sensitivity. Metformin did not affect plasma levels of thyrotropin, free thyroxine, free triiodothyronine, follicle-stimulating hormone, adrenocorticotropic hormone and insulin-like growth factor-1.

Conclusions The obtained results suggest that the effect of metformin on overactive lactotropes depends on estrogen levels.

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.

Role of Metformin in the Treatment of Patients with Thyroid Nodules and Insulin Resistance: A Systematic Review and Meta-Analysis

BACKGROUND

Metformin is the most-prescribed oral medication to lower blood glucose worldwide. Some data suggest that metformin may have a role in the treatment of patients with thyroid nodules, but contrasting results are reported in different settings. This study explores and critically reevaluates the knowledge on this topic.

METHODS

A literature search identified 250 records. Studies evaluating the size of thyroid nodules before and after metformin treatment were included. Assessed outcomes were the size of thyroid nodules, thyrotropin (TSH) level, thyroid gland volume, and insulin resistance index (HOMA-IR). After screening and full-text assessment, five studies were included in the systematic review. Random-effects meta-analyses of the standardized mean difference (SMD) were performed for the four outcomes of interest. Heterogeneity was estimated using I², and the quality of evidence was assessed for each outcome using the Grading of Recommendations Assessment, Development, and Evaluation guidelines.

RESULTS

A total of 189 patients were included in the final analysis. After metformin treatment, a slight but significant reduction in thyroid nodule size was found in four studies, which included a total of 167 patients (SMD 0.46 [confidence interval (CI) 0.00-0.93]; p = 0.05). Similarly, in four studies reporting on a total of 146 patients, significant reductions in TSH level (SMD 0.30 [CI 0.07-0.53]; p = 0.01) and HOMA-IR level (SMD 0.90 [CI 0.12-1.67]; p = 0.02) were reported after treatment with metformin. In two studies, which included 114 patients, no change in thyroid gland volume was discovered after treatment with metformin (SMD 0.21 [CI -0.05 to 0.47]; p = 0.11). Quality of evidence was generally assessed as low or very low.

CONCLUSIONS

Metformin induces reductions in thyroid nodule size and TSH and HOMA-IR levels in patients with thyroid nodules and insulin resistance. In contrast, no change in thyroid gland volumes was found. Whether metformin treatment for thyroid nodules has clinical significance remains to be demonstrated.

Effects of Metformin on TSH Levels and Benign Nodular Goiter Volume in Patients Without Insulin Resistance or Iodine Insufficiency

Objectives: To evaluate the impact of metformin (MTF) use on TSH levels, thyroid volume and volume of benign thyroid nodules (TNs). Additionally, to study if iodine status influences the outcomes. Methods: A total of 23 euthyroid patients (42 TNs) with benign thyroid nodules, diagnosed by fine needle aspiration biopsy, were randomly assigned to MTF or placebo (P) use for 6 months. Serum TSH, homeostatic model assessment for insulin resistance (HOMA-IR), and urinary iodine concentrations (UIC) were assessed. Ultrasound was used to evaluate TNs and thyroid volumes (TV) and their variations throughout the study. Diabetic patients, those undergoing levothyroxine replacement, and/or using thyroid- or insulin level-influencing drugs were excluded. Results: The sample consisted predominantly of patients without IR. Both intervention groups were similar regarding several confounding variables and showed a comparable median UIC. Serum TSH decreased significantly after MTF (-0.21 vs. 0.09 mUI/L in the P group; p = 0.015). At 6 months, no significant variations were found between groups with respect to TN volumes, TV, HOMA-IR, or body mass index (BMI). However, a tendency toward enlargement of TV with placebo (16.0%; p = 0.09) and a protective effect of MTF on growing TN (OR: 0.25; CI 0.05-1.20) was detected after excluding patients with IR (a lower UIC subgroup). The reduction on TSH levels with MTF maintained in the population without iodine insufficiency (-0.24 vs. +0.07 in the P group; p = 0.046) and was accentuated in those with excessive or more than adequate UIC (-0.69; p = 0.043). A protective effect of MTF on growing TN was suggested (OR: 0.11; IC: 0.02-0.84) in those with higher UIC. Conclusions: This study demonstrated that MTF caused a reduction in TSH levels in benign nodular goiter. This effect was more accentuated in patients with higher levels of UIC and was accompanied by a suggested protective effect on TN enlargement.

TSH evaluation in hypothyroid patients assuming liquid levothyroxine at breakfast or 30 min before breakfast

PURPOSE

To compare TSH levels of hypothyroid patients treated with liquid LT4 at breakfast or 30 min before breakfast.

PATIENTS AND METHODS

Subjects, aged 18-75 years old, were eligible if they presented hypothyroidism, due to Hashimoto's thyroiditis or after thyroidectomy for proven benign goiter. Seven hundred ninety-eight patients were recruited and enrolled in the study. Thirty-seven subjects withdrew from the trial. A total of 761 patients (mean age 46.2 ± 10.8 years) completed the study. The starting dose of LT4 was determined through clinical judgment, taking into account TSH levels, estimated residual thyroid function, age, body weight and comorbidities. All patients underwent TSH, fT4, and fT3 evaluation to verify achievement of euthyroidism with their initial fasting state assumption of LT4 after 8 weeks of therapy. If euthyroidism was not achieved, an appropriately adjusted LT4 dose was administered for 8 weeks, after which thyroid function parameters were checked again. If euthyroidism was achieved, the patients were asked to take LT4 at breakfast and hormone levels were checked again after 6 months.

RESULTS

At the end of the study period, no significant differences in serum TSH level were observed whether LT4 was ingested at breakfast or 30 min prior in a fasting state: 2.61 ± 1.79 vs. 2.54 ± 1.86 mIU/L, respectively (p = 0.455).

CONCLUSIONS

This study confirms in a large set of patients that a liquid LT4 formulation can be taken directly at breakfast and potentially improve therapeutic compliance.

TSH oscillations in young patients with type 1 diabetes may be due to glycemic variability

PURPOSE

A relationship between thyroid dysfunction and diabetes mellitus has been described by several authors but the role of glycemic variability is still unclear. We planned the present study to evaluate the influence of glycemic variability on thyroid hormones and TSH concentrations in patients with type 1 diabetes mellitus (T1DM).

METHODS

Seventy-seven young patients with T1DM were enrolled and evaluated for basal glucose concentrations, HbA1c, thyroid hormones and TSH concentrations. Glucose variability was investigated by considering the standard deviation of blood glucose readings and by calculating the mean amplitude of glycemic excursions and continuous overlapping net glycemic action (CONGA). The low (LBGI) and high (HBGI) blood glucose indices were also calculated. The correlations between TSH, thyroid hormones, glycemia and HbA1c were studied in patients and in controls, whereas those between TSH, thyroid hormones and indices of glucose variability only in patients.

RESULTS

No correlations were observed in T1DM patients between free thyroid hormones and glycemic values, HbA1c and indices of glucose variability, while an inverse correlation was observed between TSH levels and glycemic values (r = -0.27; p = 0.01), CONGA index (r = -0.35; p = 0.001) and HBGI (r = -0.28; p = 0.01) but not with HbA1c (r = -0.1; p = 0.47).

CONCLUSIONS

Our results suggest a direct action of glycemic excursions on TSH secretion, regardless of variations of thyroid hormone concentrations. Thus, the evaluation of thyroid function through the assay of TSH concentrations in these patients should be made, if possible, by multiple samples on patients in euglycemic state to avoid underestimation or overestimation of thyroid dysfunction due to a wrong diagnosis of euthyroidism or dysthyroidism with consequent inappropriate choice of therapeutic options.

Hyperthyroxinemia is positively associated with prevalent and incident type 2 diabetes mellitus in two population-based samples from Northeast Germany and Denmark

BACKGROUND AND AIMS

A potential causal relationship between thyroid function and type 2 diabetes mellitus is currently under debate, but the current state of research is limited. Our aim was to investigate the association of thyroid hormone levels with prevalent and incident type 2 diabetes mellitus (T2DM) in two representative studies.

METHODS AND RESULTS

Analyses are based on data from the Study of Health in Pomerania (SHIP), a German population based cohort with 4308 individuals at baseline and 3300 individuals at a five-year follow-up, and from INTER99, a Danish population-based randomized controlled trial with 6784 individuals at baseline and 4516 individuals at the five-year-follow-up. Serum thyroid-stimulating hormone (TSH) and free thyroxine (fT4) concentrations were measured in both studies, while free triiodothyronine was measured in SHIP only. T2DM was defined by self report or intake of anti-diabetic medication. Neither in SHIP nor in INTER99 we detected significant associations of serum TSH levels with prevalent or incident T2DM. Serum fT4 levels were significantly positively associated with prevalent T2DM in SHIP and INTER99. In longitudinal analyses baseline levels of fT4 were significantly positively associated with incident T2DM in SHIP (RR per pmol/L = 1.07; 95%-CI = 1.05-1.10), while this association barely missed statistical significance in INTER99 (RR per pmol/L = 1.03; 95%-CI = 0.99-1.06). In SHIP baseline fT3 levels were significantly associated with incident T2DM (RR per pmol/L = 1.21; 95%-CI = 1.16-1.27).

CONCLUSION

We demonstrated positive associations of thyroid hormones with prevalent and incident type 2 diabetes mellitus suggesting that hyperthyroxinemia may contribute to the pathogenesis of this condition.

Thyroid Status in Patients with Type 2 Diabetes Attending a Tertiary Care Hospital in Eastern India

OBJECTIVE

Type 2 diabetes mellitus and thyroid dysfunction (TD) are two major public health endocrine problem, but the prevalence of TD and iodine status in patients with T2 DM in India is less studied. The study objective was to explore the prevalence of TD and to evaluate iodine health in type 2 diabetes patients attending a tertiary care center in Eastern India.

METHODS

Consecutive 100 patients with diabetes attending outpatient department were evaluated clinically and biochemically (thyrotropin [TSH], free thyroxine, anti-TPO antibody, and urinary iodine). We excluded pregnant women or patients taking drugs that can alter thyroid function. Subclinical hypothyroid and overt hypothyroidism were diagnosed as per standard definitions.

RESULTS

Out of 100 patients were analyzed, 51 (51%) were male. Mean (±standard deviation) age was 45.4 ± 11.2 years, body mass index 24.1 ± 4.28 kg/m², and duration of diabetes 7.76 ± 5.77 years. The prevalence of subclinical hypothyroidism and overt hypothyroidism was 23/100 (23%) and 3/100 (3%), respectively. Thyroid autoantibody was positive in 13 (13.1%) patients. All patients were iodine sufficient. A trend toward increased neuropathy (r = 0.45) and nephropathy (r = -0.29) was associated with rising TSH.

CONCLUSION

Almost one in four people living with diabetes are suffering from TD. Thus, routine screening should be implemented. Salt iodination program is a huge success in this part of the country.

Relationship between Thyroid Function and Kidney Function in Patients with Type 2 Diabetes

PURPOSE

To determine if the TSH is related to estimated glomerular filtration rate (eGFR) in T2D patients without overt thyroid dysfunction.

METHODS

A cohort study of 5936 T2D patients was assessed for thyroid and kidney functions, in whom 248 with subclinical hyperthyroidism and 362 with subclinical hypothyroidism. Serum creatinine and 24-hour urine albumin excretion (UAE) were collected. Chronic kidney disease (CKD) was defined as eGFR < 60 ml/min/1.73 m².

RESULTS

Compared with euthyroid subjects, the patients with subclinical hypothyroidism had lower eGFR (82.7 ± 22.4 vs. 90.5 ± 22.4 ml/min/1.73 m², p < 0.01), higher UAE (114 ± 278 vs. 88 ± 229 mg/24 h, p < 0.05), and high incidence of CKD (16.0% vs. 10.1%, p < 0.05). The participants with a TSH level between 0.55 and 3.0 μIU/ml had a higher eGFR (91.4 ± 22.2 ml/min/1.73 m²) and a lower prevalence of CKD (9.5%) than those with higher TSH (3.01-4.78 μIU/ml, 85.6 ± 22.7 ml/min/1.73 m², p < 0.01 and 13.1%, p < 0.01). Linear logistic regression analysis showed that the eGFR was significantly negatively associated with TSH (OR: 0.519, 95% CI: 0.291-0.927, p < 0.05), after adjustment of confounders.

CONCLUSION

High TSH was independently associated with decreased eGFR in type 2 diabetes patients without overt thyroid dysfunction. Our findings indicate that doctors who treat T2D patients should routinely measure the thyroid function.

Metformin effect on TSH in subclinical hypothyroidism: randomized, double-blind, placebo-controlled clinical trial

INTRODUCTION

Non-randomized trials suggest that metformin may reduce TSH levels through unknown mechanisms.

OBJECTIVE

To evaluate whether metformin can reduce TSH levels in subjects with subclinical hypothyroidism.

PATIENTS AND METHODS

This is a randomized, double-blind, placebo controlled clinical trial with 3 months duration that enrolled 48 individuals, between 18 and 65 years, with subclinical hypothyroidism. The patients were randomized to the use of metformin 850 mg or placebo twice a day for 3 months. The primary outcome was the absolute decrease in TSH levels. Secondary outcomes were changes in the clinical and laboratory assessment, as well as in blood pressure assessed by ambulatory blood pressure monitoring.

RESULTS

After 3 months, 93.75% of participants completed the follow-up. The post treatment value of TSH in the metformin and placebo groups were 6.48 ± 3.11 and 7.02 ± 3.28 mIU/L, respectively (p = 0.57). Patients who achieved status of euthyroidism in the metformin and placebo groups were 21.7 and 18.2%, respectively (p = 0.76). There was no significant reduction of TSH within the groups [delta for TSH of 0.63 ± 0.56 (p = 0.28) and 0.54 ± 0.60 mIU/L (p = 0.38), in metformin and placebo groups, respectively]. There was a small increase in HDL cholesterol (1.62 ± 0.45 vs. 1.34 ± 0.39 mmol/L, p = 0.03) favoring the metformin group.

CONCLUSION

Since the sample size was small, the study was inconclusive and the results should be considered preliminary data of a study that needs to enroll 1626 patients to show a 0.5 mIU/L difference in TSH between the groups, with 90% power.

Efficacy of Metformin for Benign Thyroid Nodules in Subjects With Insulin Resistance: A Systematic Review and Meta-Analysis

Background: To evaluate the effect of metformin therapy on decreasing benign thyroid nodule volume in subjects with insulin resistance (IR). Method: Randomized controlled trials (RCTs) and self-controlled trials for the meta-analysis published, before January 31, 2018 were selected from the PubMed, Cochrane Library, Embase, Web of Science, Chinese Biomedical Literature Database, National Knowledge Infrastructure, WANFANG and VIP Database. Pooled standard mean difference with 95% confidence interval was estimated by fixed- or random-effects model depending on heterogeneity. The risk of bias using the Cochrane Collaboration's tool was used to assess the quality of the RCTs contained. The quality of self-controlled studies was evaluated using the Methodological index for non-randomized studies (MINORS) method. Results: 7 studies (3 RCTs and 4 prospective self-controlled studies) with 240 patients were considered to be appropriate for the meta-analysis. The results of the meta-analysis indicated that the volume of thyroid nodule decreased significantly after metformin therapy (SMD -0.62, 95% CI -0.98 ~ -0.27). 6 studies reported the changes of the level of TSH. TSH levels decreased significantly after metformin therapy (SMD -0.27, 95% CI -0.47 ~ -0.07). The pooled data indicated an increase in FT3 level, and an unchanged FT4 level after metformin therapy (FT3, SMD 0.25, 95% CI 0.05 ~ 0.45; FT4, SMD -0.07, 95% CI -0.27 ~ 0.13). HOMA-IR levels decreased significantly after metformin therapy based on the pooled results of 3 RCTs and 3 prospective self-controlled studies (SMD -1.08, 95% CI -1.69 ~ -0.47). Conclusion: The meta-analysis demonstrated that metformin was safe and useful in shrinking benign thyroid nodules volume, improving thyroid function and IR. A large number of high-quality prospective studies still need to be carried out.