Can levothyroxine treatment reduce urinary albumin excretion rate in patients with early type 2 diabetic nephropathy and subclinical hypothyroidism? A randomized double-blind and placebo-controlled study

Relationship of Thyroid Function with Renal Hemodynamics and Cholesterol Metabolism in Proteinuric Kidney Disease: A Pilot Study

Nephrotic syndrome and hypothyroidism are respectively reported to influence renal hemodynamics and hypercholesterolemia. However, the relationship of proteinuria-associated thyroid function with renal hemodynamics and cholesterol metabolism has yet to be determined in a simultaneous analysis of thyroid, renal, and cholesterol variables. We investigated the hypothesis that the changes in thyroid hormones by proteinuria may contribute to changes in cholesterol metabolism and renal hemodynamics by proteinuria. Twenty-nine patients (17 men and 12 women) with proteinuric kidney disease (mean age 46 years) were enrolled in a pilot study. Data for serum free triiodothyronine (FT3), free thyroxine (FT4), total cholesterol, and filtration fraction (FF; assessed by para-aminohippuric acid clearance) were used in variable-adjusted correlation analyses. The patients had the following data (mean ± standard deviation): urinary protein 5.18 ± 3.28 g/day, FT3 2.18 ± 0.44 pg/mL, FT4 1.03 ± 0.26 ng/dL, FF 0.27 ± 0.07, and total cholesterol 327 ± 127 mg/dL. There was a significant positive correlation of FT3 with FF (β = 0.58, p = 0.01) and a significant inverse correlation of FT4 with total cholesterol (β = -0.40, p = 0.01). A positive correlation of FT3 with FF and an inverse correlation of FT4 with total cholesterol were demonstrated in patients with proteinuric kidney disease. The proteinuria-associated reduction in serum thyroid hormone levels was correlated with hypercholesterolemia and the reduced glomerular FF. Further studies of these relationships are required.

Systematic review and meta-analysis of levothyroxine effect on blood pressure in patients with subclinical hypothyroidism

This study aims to evaluate the effect of levothyroxine therapy on blood pressure (BP) in patients with subclinical hypothyroidism (SCH). Were searched Six databases, and randomized controlled trials (RCT) and prospective cohort studies evaluating the effect of levothyroxine therapy on BP in patients with SCH were included. 37 articles (9 RCTs and 28 prospective cohorts) were included in this meta-analysis. Pooled analysis of RCT studies was insignificant; however, pooled analysis of 28 prospective cohort studies showed a significant difference before and after the therapy, reducing both systolic blood pressure (SBP) and diastolic blood pressure (DBP) (MD=-4.02 [-6.45, -4.58] and MD=-2.13 [-3.69, -0.56], both P-values<0.05). Levothyroxine therapy can play a role in lowering BP in patients with SCH. However, this effect is more observed in Caucasians, SCH patients with higher initial TSH followed by more remarkable TSH change to normal levels, and SCH patients with hypertension.

Analysis of Thyroid Function in ANCA-Associated Vasculitis Patients with Renal Injury

BACKGROUND

Previous studies indicated common thyroid dysfunction in various kidney diseases. This study aimed to investigate the thyroid function in patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV) with renal injury.

METHODS

Briefly, 174 patients diagnosed as having AAV with renal injury and without previous thyroid disease history were included in the retrospective and prospective study. The clinical parameters were collected and compared between different groups.

RESULTS

Of the patients included, 24 exhibited normal thyroid function, while 150 had thyroid dysfunction, including 55 (36.67%) with hypothyroidism. Those AAV patients with thyroid dysfunction showed different clinical parameters from those with normal thyroid function. The patients were followed up for a median of 68.6 (64.3; 72.8) months. Those with thyroid dysfunction were more prone to progressing to dialysis dependence compared to the group with normal thyroid function. Logistic regression analysis showed advanced age and decreased albumin as independent risk factors for thyroid dysfunction in patients with AAV. Survival analysis and multivariate Cox regression analysis showed that thyroid dysfunction was a risk factor for AAV patients with renal injury to progress to the endpoint of dialysis dependence.

CONCLUSION

Thyroid dysfunction, predominantly hypothyroidism, was commonly complicated in AAV patients with renal injury. AAV patients with thyroid dysfunction were presented with different clinical parameters and more prone to progressing to dialysis dependence compared to those with normal thyroid function.

Protocol and Methods: Role of Levothyroxine on the Progression of Chronic Kidney Disease in Subclinical Hypothyroid Populations (LP-CKD) - A Multicenter Randomized Controlled Trial

Introduction

Subclinical hypothyroidism (SCH) is highly prevalent and associated with chronic kidney disease (CKD). However, it is still unanswered whether the restoration of euthyroid status in these patients will be beneficial in retarding a decline in glomerular filtration rate in early CKD patients. We aim to evaluate the efficacy of levothyroxine therapy versus placebo in slowing estimated glomerular filtration rate (eGFR) decline among CKD patients (stage 2-4) with SCH.

Methods

This study will be a multicentric, double-blind, randomized, parallel-group, placebo-controlled study. A total of 500 CKD patients, 250 patients in the treatment group and 250 patients in the placebo group, will be randomized. The randomization between the treatment arm and placebo arm will be performed as per the computer-generated random number table in a 1:1 ratio. The sample size was calculated based on the assumed reduction in eGFR after 1-year follow-up in the treatment and placebo groups of 10% and 25%, respectively, at a minimum two-sided 99% confidence interval and 90% power of the study and considering 20% loss on follow-up. Each patient will be followed every 3 months for at least 1 year after randomization. Individuals completing 1-year follow-up visits will be considered for analysis. The baseline and follow-up data will be compared between the treatment and placebo groups. The study will evaluate the efficacy and safety of levothyroxine therapy versus placebo in slowing eGFR decline among CKD patients (stage 2-4) with SCH. The primary endpoint will be the end of follow-up of the patients, reduction of eGFR by ≥50% from a baseline of that patient, or development of ESKD or death of the patients. The secondary endpoint will be any cardiovascular event or arrhythmia after the institution of the drug.

Management of traditional risk factors for the development and progression of chronic kidney disease

Chronic kidney disease (CKD) and its downstream complications (i.e. cardiovascular) are a major source of morbidity worldwide. Additionally, deaths due to CKD or CKD-attributable cardiovascular disease account for a sizeable proportion of global mortality. However, the advent of new pharmacotherapies, diagnostic tools, and global initiatives are directing greater attention to kidney health in the public health agenda, including the implementation of effective strategies that (i) prevent kidney disease, (ii) provide early CKD detection, and (iii) ameliorate CKD progression and its related complications. In this Review, we discuss major risk factors for incident CKD and CKD progression categorized across cardiovascular (i.e. hypertension, dyslipidemia, cardiorenal syndrome), endocrine (i.e. diabetes mellitus, hypothyroidism, testosterone), lifestyle (i.e. obesity, dietary factors, smoking), and genetic/environmental (i.e. CKDu/Mesoamerican nephropathy, APOL1, herbal nephropathy) domains, as well as scope, mechanistic underpinnings, and management.

Systematic Review to Gauge the Effect of Levothyroxine Substitution on Progression of Diabetic Nephropathy in Patients With Hypothyroidism and Type 2 Diabetes Mellitus

Diabetes mellitus (DM) and thyroid dysfunction are two disorders that are closely related. This systematic review aimed to investigate the effect of levothyroxine supplementation on diabetic nephropathy in type 2 diabetic patients with co-existing thyroid dysfunction. We explored medical databases such as PubMed, Medline, Multidisciplinary Digital Publishing Institute (MDPI), and Cochrane Library for relevant medical literature. The papers were screened, and 12 research papers involving 10,371 patients were identified after applying eligibility criteria and quality assessment using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The included papers analyzed the effect of aberrant thyroid profile on kidney disease in diabetic individuals and the role that achieving euthyroid status with levothyroxine supplementation could play in diabetic nephropathy. Reduced free triiodothyronine (FT3) was the most common independent factor associated with diabetic microvascular and macrovascular complications. Levothyroxine (LT4) regimen was more effective than the placebo in lowering urinary albumin excretion rate (UAER), low-density lipoprotein cholesterol, and uric acid and decreasing oxidative stress overall. However, replacement therapy's effect may differ in the short and long terms. Thyroid hormone replacement therapy (THRT) may reduce the risk of diabetic nephropathy and cardiovascular disease (CVD) development in hypothyroid patients, but more randomized trials are needed to confirm the effect of THRT.

Low glomerular filtration rate values are associated with higher TSH in an elderly population at high cardiovascular disease risk

Background

Hypothyroidism is associated with impaired glomerular filtration rate (GFR), a recognized cardiovascular disease (CVD), and mortality risk factor. In older adults, this association remains unexplored. We aimed to determine the relationship of elevated TSH with GFR in an elderly population at high CVD risk.

Methods

Older adults (age>65ys) with high CVD risk defined by two or more CVD risk factors: smoking (S), high blood pressure (HBP), high total cholesterol, low HDL cholesterol, diabetes (DM), metabolic syndrome or previous cardiovascular event, were prospectively included at our ambulatory Endocrine Clinic. Patients under levothyroxine or thyroid disease were excluded. TSH> 6mU/l defined subclinical hypothyroidism (ScH) with normal free T4 levels. Estimated GFR was calculated by the Berlin-Initiative Study (BIS)-1 formula for elderly population. Urinary albumin to creatinine ratio (uACR), IL-6 and TNF-α, and Carotid intima-media thickness (CIMT) were also determined. The U Mann-Whitney test, the Spearman test, and multiple linear regression were used as statistical tests.

Results

Finally 246 patients (68% females) were included and 20 (8%) had ScH. This group, was older (median, Q1-Q3: 77,72-78; 72,68-77 years, p=0.01) and DM was less frequent than in the euthyroid group (35 vs 58%, p=0.039). Lower fasting glucose (-20%,p=0.01), GFR (-14%,p=0.01) and freeT4 (-10%,p<0.001) were found compared to euthyroid patients. A higher prevalence of Kidney failure was found in ScH (80 vs. 46%, p=0.003) vs. euthyroid individuals. Significant correlations with GFR were detected: age (r-0.482,p<0.001), TSH (r-0.172,p=0.004), IL-6 (r-0.150,p=0.047), TNF-α (r-0.274,p<0.001), uACR (r-0.170,p=0.009) and CIMT(r-0.189,p=0.004). By multiple linear regression, in a model adjusted by age, sex, BMI, uACR, S, DM, TNF-α and HBP, TSH (Bst -0.14, p=0.023, R2 = 0.25) was found an independent predictor of GFR.

Conclusion

In older adults with high CVD risk, ScH is associated with lower renal function, and this relationship is present regardless of other cardiometabolic risk factors. These results suggest that ScH could contribute to low GFR and excess CVD risk, although this hypothesis should be addressed in longitudinal studies.

Subclinical hypothyroidism, outcomes and management guidelines: a narrative review and update of recent literature

Subclinical hypothyroidism (SCH) is diagnosed when serum thyroid stimulation hormone (thyrotropin; TSH) levels are above the reference range, accompanied by levels of free thyroxine within its reference range. The management of SCH remains a diagnostic and therapeutic challenge despite many years of research relating to its epidemiology, aetiology, effectiveness of treatment and safety. European Thyroid Association (ETA) guidelines for the management of SCH were published almost a decade ago. This narrative review summarizes the clinical literature relating to SCH and outcomes since the publication of these guidelines. Clinical evidence emerging during the previous decade generally supports the view that SCH is associated with adverse outcomes to an extent that is intermediate between euthyroidism and overt hypothyroidism although evidence that treatment with thyroid hormone replacement is beneficial is lacking. Accordingly, the rationale for the recommendations for intervention in the ETA guidelines based on the age of the patient, level of serum TSH, symptoms and comorbidities remains valid today.

The Correlation between Thyroid Hormone Levels and the Kidney Disease Progression Risk in Patients with Type 2 Diabetes

OBJECTIVE

We investigated the relationship between thyroid hormones and the risk of diabetic kidney disease (DKD) progression.

METHODS

A total of 452 patients with type 2 diabetes were included, and a cross-sectional analysis was performed. Urine albumin/creatinine ratio (ACR) and estimated glomerular filtration rate (eGFR) were used to diagnose persistent albuminuria and stage chronic kidney disease, respectively. The Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline was used to describe the risk of DKD progression (low, moderate, and high or very high risks).

RESULTS

The DKD group had higher levels of thyroid-stimulating hormone (TSH) and lower levels of free triiodothyronine (FT3) and free thyroxine (FT4) than the non-DKD group. The prevalence of thyroid dysfunction in the DKD group was significantly higher than in the non-DKD group, especially the prevalence of subclinical hypothyroidism. FT3 levels decreased gradually with the deterioration of DKD. TSH levels increased with an increasing KDIGO category. FT3 and FT4 levels were negatively correlated with serum creatinine levels and ACR, and positively correlated with eGFR. Contrastingly, TSH was positively correlated with ACR, and negatively correlated with eGFR. After adjustment, an increase in FT3 levels significantly reduced the risk of DKD [odds ratio, OR (95% confidence interval, CI)=0.58 (0.42-0.79)] and DKD progression [ORs (95% CIs)=0.65 (0.45-0.93) for the moderate risk group and 0.50 (0.33-0.74) for the high or very high-risk group, using the low-risk group as a reference]. FT3 levels below 4.30 pmol/L in men and 3.99 pmol/L in women were the cut-off points for an increased risk of DKD progression.

CONCLUSION

Low FT3 level is an independent risk factor for DKD and DKD progression. FT3 ≤4.30 pmol/L in men and ≤3.99 pmol/L in women will greatly increase the risk of kidney disease progression in patients with type 2 diabetes.

Association of Thyroid Hormone Levels with Microvascular Complications in Euthyroid Type 2 Diabetes Mellitus Patients

PURPOSE

To examine the prevalence of different microvascular complications and investigate the association between thyroid hormones (THs) and these complications in euthyroid patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 248 T2DM patients were analyzed retrospectively for the study. All patients received a detailed and standard assessment to identify diabetic peripheral neuropathy (DPN), diabetic nephropathy (DN), and diabetic retinopathy (DR). Multivariate logistic regression was carried out to analyze the association between THs and diabetic microvascular complications.

RESULTS

The study found the prevalence of any microangiopathy to be 72.18% (n = 179). At the same time, the prevalence of DPN was 54.84% (n=136), while that of DN was 31.85% (n=79). Likewise, the prevalence of DR was 35.48% (n=88). The odds ratios (ORs) for free triiodothyronine (FT3) developing any microangiopathy, DPN, DN and DR were 0.200, 0.361, 0.310, and 0.588 (P<0.05), respectively. Also, the ORs for free thyroxine (FT4) developing any microangiopathy, DPN, DN and DR were 0.643, 0.800, 0.702 and 0.726 (P<0.05), respectively. Lastly, the ORs for thyroid-stimulating hormone (TSH) developing DPN was 1.57 (95% CI: 1.148-2.137, P=0.005).

CONCLUSION

The study concludes that serum FT3 and FT4 levels are negatively associated with any microangiopathy, DPN, DN and DR in euthyroid patients with T2DM, independent of traditional risk factors. However, the TSH levels are positively associated with DPN. Future larger sample-size studies are needed to confirm the relationship between thyroid hormone levels and microvascular complications in euthyroid patients with T2DM.

Thyroid hormone status in patients with impaired kidney function

PURPOSE

We aimed to investigate the prevalence of thyroid hormone abnormalities and the relationship between free triiodothyronine (fT3), thyroid stimulating hormone (TSH) and free thyroxine (fT4) serum levels with kidney function and proteinuria in 4108 subsequent patients admitted to a Nephrology Clinic at a tertiary Medical Centre.

METHODS

All patients were categorized based on their estimated glomerular filtration rate (eGFR) as follows: normal-eGFR ≥ 60 ml/min, mild kidney impairment-30 ≤ eGFR < 60 ml/min, and severe kidney impairment-eGFR < 30 ml/min.

RESULTS

Subjects with normal eGFR presented a laboratory constellation of hypothyroidism in 3.38% and "low-T3 syndrome" in 8.28%, while subjects with severe kidney impairment were diagnosed with hypothyroidism in 2.82% and "low-T3 syndrome" in 22.9%. Multivariate regression analysis showed that eGFR was a strong independent predictor of serum fT3 levels in patients with eGFR < 60 ml/min. Impaired kidney function was associated with low fT4 and fT3 but not TSH. Our findings showed an inverse correlation of fT3 and fT4 levels and proteinuria range. FT4 inversely correlated with the extent of proteinuria in all subgroups of patients. In contrast, the inverse correlation of fT3 serum levels and proteinuria disappeared in patients with eGFR < 60 ml/min.

CONCLUSION

In a large cohort of inpatients, the prevalence of low-T3 syndrome was 2.5 times higher in patients with advanced kidney disease, compared to those with normal kidney function. In advanced CKD, both eGFR and proteinuria were strongly correlated with thyroid hormones. Therefore, close screening of the "thyroid profile" in patients with any stage of CKD, especially to those with proteinuria, might be warranted.

Levothyroxine in the treatment of overt or subclinical hypothyroidism: a systematic review and meta-analysis

The goal of this study was to review relevant randomized controlled trials in order to determine the clinical efficacy of levothyroxine in the treatment of overt or subclinical hypothyroidism. Using appropriate keywords, we identified relevant studies using PubMed, the Cochrane library, and Embase. Key pertinent sources in the literature were also reviewed, and all articles published through December 2019 were considered for inclusion. For each study, we assessed odds ratios (ORs), mean difference (MD), and 95% confidence interval (95%CI) to assess and synthesize outcomes. We included 25 studies with totally 1,735 patients in the meta-analysis. In the patients with hypothyroidism, compared with L-T4, L-T4 plus L-T3 significantly decreased TSH levels and increased FT3 levels. Compared with placebo, L-T4 significantly increased FT4 levels and decreased TSH levels. In patients with subclinical hypothyroidism, compared with placebo, L-T4 significantly decreased SBP, TSH, T3 and TC and increased FT3 and FT4.

Hypothyroidism and Kidney Function: A Mendelian Randomization Study

Background: Uncertainty in the mechanism and directionality of observational associations between thyroid function and kidney function may be addressed by genetic analysis with an instrumental variable method termed bidirectional Mendelian randomization (MR). Methods: In the Women's Genome Health Study (WGHS), observational associations between thyroid measures and kidney function were evaluated. Genetic instruments for MR were from recent genome-wide association studies (GWAS) of hypothyroidism, thyrotropin (TSH), and free thyroxine (fT4) concentrations within the reference range, thyroid peroxidase antibodies (TPOAb), estimated glomerular filtration rate from creatinine (eGFR_crea), eGFR from cystatin C (eGFR_cys), and chronic kidney disease (CKD). In WGHS individual-level data, these instruments were used for bidirectional MR between thyroid (N = 3336) and kidney (N = 23,186) functions. To increase power, MR was also performed using GWAS summary statistics from the Chronic Kidney Disease Genetics Consortium (CKDGen) for eGFR_crea (N = 567,460), eGFR_cys (N = 24,063), CKD [N(total) = 480,698, N(cases) = 41,395], and urinary albumin/creatinine ratio (UACR/N = 54,450). Results: In the WGHS, hypothyroidism was observationally associated with decreased eGFR_crea [beta (standard error, SE): -0.024 (0.009) ln(mL/min/1.73 m²), p = 0.01]. By MR, hypothyroidism was associated with decreased eGFR_crea in the WGHS [beta (SE): -0.007 (0.002) per doubled odds hypothyroidism, p = 1.7 × 10^-3] and in CKDGen [beta (SE): -0.004 (0.0005), p = 2.0 × 10^-22], and robust to sensitivity analysis. Hypothyroidism was also associated by MR with increased CKD in CKDGen (odds ratio, OR [confidence interval, CI]: 1.05 [1.03-1.08], p = 3.3 × 10^-5), but not in the WGHS (OR [CI]: 1.02 [0.95-1.10], p = 0.57). Increased TSH within the reference range had an MR association with increased eGFR_crea in the WGHS [beta (SE): -0.018 (0.007) ln(mL/min/1.73 m²)/standard deviation, SD, p = 6.5 × 10^-3] and CKDGen [beta (SE): -0.008 (0.001) ln(mL/min/1.73 m²)/SD, p = 6.8 × 10^-17], and with CKD in CKDGen (OR [CI]: 1.10 [1.04-1.15], p = 3.1 × 10^-4). There were no MR associations of hypothyroidism or TSH with eGFR_cys or UACR, and MR associations of fT4 in the reference range with kidney function were inconsistent in both the WGHS and CKDGen. However, by MR in CKDGen, TPOAb were robustly associated with decreased eGFR_crea [beta (SE): -0.041 (0.009), p = 6.2 × 10^-6] and decreased eGFR_cys [beta (SE): -0.294 (0.065), p = 6.2 × 10^-6]. TPOAb were less robustly associated with CKD but not associated with UACR. In reverse MR in the WGHS, kidney function was not consistently associated with thyroid function. Conclusions: Bidirectional MR supports a directional association from hypothyroidism, increased TSH, and TPOAb, but not fT4, to decreased eGFR_crea and increased CKD.

Screening for thyroid dysfunction and treatment of screen-detected thyroid dysfunction in asymptomatic, community-dwelling adults: a systematic review

BACKGROUND

This systematic review was conducted to inform the Canadian Task Force on Preventive Health Care recommendations on screening for thyroid dysfunction (TD). The review sought to answer key questions on the benefits and harms of screening for TD, patients' values and preferences for screening, and the benefits and harms of treating screen-detected TD.

METHODS

This review followed Canadian Task Force on Preventive Health Care methods, which include the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. The search strategy used for benefits and harms of screening and treatment was an update to the 2014 review by the US Preventive Services Task Force and searched MEDLINE and the Cochrane Library. MEDLINE, Embase, ProQuest Public Health, and SCOPUS were searched for patients' values and preferences for screening. Outcomes of interest included all-cause mortality, deaths due to cardiovascular diseases, fatal and non-fatal cardiovascular events, atrial fibrillation, fractures, quality of life, cognitive function, and harms due to TD treatment. Two reviewers independently screened abstracts and full texts according to pre-determined inclusion criteria and assessed the risk of bias for each study included. Strength and quality of the evidence was assessed for each outcome. A narrative synthesis was conducted due to heterogeneity of the included studies.

RESULTS

No studies were found on screening for TD, treatment of subclinical hyperthyroidism, or patients' values and preferences for screening for TD. Twenty-two studies (from 24 publications) on the treatment of TD in patients with screen-detected subclinical hypothyroidism were included. Results from the included randomized controlled trials suggested no benefit of treatment for subclinical hypothyroidism for the large majority of outcomes. We found very low-quality evidence (from two cohort studies) for a small reduction in all-cause mortality among adults < 65 or 40-70 years who were treated for TD compared to those who were not.

CONCLUSIONS

This review found moderate to very low-quality evidence on the benefits and harms of treatment for subclinical hypothyroidism, with most of the evidence showing no benefit of treatment.

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.

Association between thyroid function and diabetic nephropathy in euthyroid subjects with type 2 diabetes mellitus: a cross-sectional study in China

Previous studies have suggested that even in euthyroid subjects, thyroid function may affect the risk factors of diabetic nephropathy (DN). Thus, we investigated the association between thyroid parameters and DN in euthyroid subjects with type 2 diabetes mellitus (T2DM). This was a cross-sectional study of 1,071 euthyroid subjects with T2DM (mean age of 61.90 ± 12.74 years; 622 men). Clinical factors, including levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), thyroid autoantibodies, albumin excretion rate were measured. DN was present in 400 (37.35%) individuals. Patients with DN exhibited higher serum TSH and lower serum FT3 and FT4 levels than those without DN (P<0.05). After adjusting traditional risk factors of DN, the levels of both FT3 (per-SD increase, odds ratio [OR] 0.606 [95% confidence interval (CI), 0.481-0.762], P<0.001) and FT4 (per-SD increase, OR 0.944 [0.894-0.998], P = 0.040) were inversely correlated with DN. Meanwhile, we found that serum TSH levels were positively correlated with DN (per-SD increase, OR1.179 [1.033-1.346], P = 0.015). Low-to-normal thyroid hormones (THs) were also associated with the presence of macroalbuminuria. In conclusion, the relatively low levels of THs were significantly associated with DN in euthyroid subjects with T2DM.

Effect of Levothyroxine on Blood Pressure in Patients With Subclinical Hypothyroidism: A Systematic Review and Meta-Analysis

Background: Patients with subclinical hypothyroidism (SCH) have elevated blood pressure, but the effect of levothyroxine (LT4) therapy on blood pressure among those patients is still unclear. This study aimed to assess whether LT4 therapy could reduce blood pressure in SCH patients through a systematic review and meta-analysis. Methods: PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science were searched. Randomized controlled trials (RCTs) assessing the effect of LT4 therapy on blood pressure or prospective follow-up studies comparing the blood pressure level before and after LT4 treatment were included, and the mean difference of systolic blood pressure (SBP) or diastolic blood pressure (DBP) was pooled using random-effect meta-analysis. Results: Twenty-nine studies including 10 RCTs and 19 prospective follow-up studies were eligible for the analysis. Meta-analysis of 10 RCTs suggested that LT4 therapy could significantly reduce SBP in SCH patients by 2.48 mmHg (95% CI -4.63 to -0.33, P = 0.024). No heterogeneity was observed among these 10 RCTs (I² = 0%). Meta-analysis of the 19 prospective follow-up studies found that LT4 therapy significantly decreased SBP and DBP by 4.80 mmHg (95%CI -6.50 to -3.09, P < 0.001) and 2.74 mmHg (95%CI -4.06 to -1.43, P < 0.001), respectively. Conclusion: The findings suggest that LT4 replacement therapy can reduce blood pressure in SCH patients, which needs to be validated in more clinical trials with larger samples.

The effect of L-thyroxine substitution on oxidative stress in early-stage diabetic nephropathy patients with subclinical hypothyroidism: a randomized double-blind and placebo-controlled study

PURPOSE

To study oxidative stress status of early type 2 diabetic nephropathy (DN) patients with subclinical hypothyroidism (SCH) and to assess effect of L-thyroxine therapy on the oxidative stress in these patients.

METHODS

It is a randomized double-blind and placebo-controlled trial. A total of 48 patients with early type 2 DN were included as Euthyroid group, and 92 early type 2 DN with SCH were selected and randomly assigned to L-thyroxine treatment group (LT4 group) and placebo group (SCH group). Changes in urinary albumin excretion rate (UAER), serum malondialdehyde (MDA), superoxide dismutase (SOD) activity, urine 8-hydroxyl deoxyguanosine (8-OHdG), serum creatinine, estimated glomerular filtration rate, and lipid profile before and after 24 weeks of follow-up were examined and compared.

RESULTS

The levels of UAER, MDA, 8-OHdG were higher, while the SOD activity was lower in DN patients with SCH than in DN patients (p < 0.05 for all). In the LT4 group, the levels of UAER, MDA, 8-OHdG decreased significantly (p < 0.05) to levels no longer different from the Euthyroid group. The SOD activity increased significantly. But in SCH group, the levels of mAlb, MDA, 8-OHdG were greater after 24 weeks of follow-up and greater than patients in the Euthyroid group. SOD activity decreased significantly after 24 weeks in the SCH group (p < 0.05).

CONCLUSION

Oxidative stress is greater in the DN patients with SCH, and SCH may exacerbate kidney injury in early DN patients. The LT4 treatment may decrease the oxidative stress and attenuate renal injury in DN patient with SCH.

The lipid-lowering effect of levothyroxine in patients with subclinical hypothyroidism: A systematic review and meta-analysis of randomized controlled trials

OBJECTIVES

Dyslipidaemia is common in patients with subclinical hypothyroidism (SCH). To date, there is no universal agreement regarding the lipid-lowering effect of substitution treatment with L-T4 in patients with SCH. We aimed to clarify the effect by conducting this systematic review and meta-analysis of randomized controlled trials (RCTs).

DESIGN

We systematically searched PubMed, the Cochrane Library, ClinicalTrials.gov and EMBASE for RCTs comparing substitution treatment to placebo treatment or observation. We focused on the primary outcomes of changes from baseline of total, low-density lipoprotein and high-density lipoprotein cholesterol (TC, LDL-C and HLD-C) and triglycerides. Subgroup analyses were performed, assessing the effect of treatment duration, disease severity and ethnicity on the occurrence of discrepancy.

RESULTS

Twelve trials, with 940 participants, were eligible for analysis. Compared with the control group, levothyroxine substitution yielded a mean reduction in TC (-0.29 mmol/L, [-0.42 to -0.16]) and LDL-C (-0.22 mmol/L, [-0.36 to -0.09]), with no significant effects on HDL-C (-0.04 mmol/L, [-0.08 to 0.01]) or triglycerides (-0.04 mmol/L, [-0.08 to 0.00]). Trials in which only patients with mild SCH (thyrotropin <10 mIU/L) were enrolled showed equivalent effects. The lowering effects were weaker, but still significant, in long-term treatment (>6 months) compared with short-term treatment (≤6 months) for TC (-0.19 mmol/L [-0.35, -0.03] vs -0.50 mmol/L [-0.68, -0.31], P=.047) and LDL-C (-0.09 mmol/L [-0.16, -0.02] vs -0.46 mmol/L [-0.68, -0.25], P=.006).

CONCLUSIONS

Levothyroxine treatment has clear benefits on TC and LDL-C in SCH patients, including those with mild SCH.

The interaction between thyroid and kidney disease: an overview of the evidence

PURPOSE OF REVIEW

Hypothyroidism is highly prevalent in chronic kidney disease (CKD) patients, including those receiving dialysis. This review examines potential mechanistic links between thyroid and kidney disease; current evidence for hypothyroidism as a risk factor for de novo CKD and CKD progression; and studies of thyroid functional disorders, cardiovascular disease, and death in the CKD population.

RECENT FINDINGS

Epidemiologic data have demonstrated an incrementally higher prevalence of hypothyroidism with increasing severity of kidney dysfunction. Various thyroid functional test abnormalities are also commonly observed in CKD due to alterations in thyroid hormone synthesis, metabolism, and regulation. Although the mechanistic link between thyroid and kidney disease remains unclear, observational studies suggest that hypothyroidism is associated with abnormal kidney structure and function. Previously thought to be a physiologic adaptation, recent studies show that hypothyroidism is associated with higher risk of cardiovascular disease and death in CKD.

SUMMARY

A growing body of evidence suggests that hypothyroidism is a risk factor for incident CKD, CKD progression, and higher death risk in kidney disease patients. Rigorous studies are needed to determine the impact of thyroid hormone replacement upon kidney disease progression, cardiovascular disease, and mortality, which may shed light onto the causal implications of hypothyroidism in CKD.