Thyroid function, reduced kidney function and incident chronic kidney disease in a community-based population: the Atherosclerosis Risk in Communities study

The association of thyroid hormone levels and incidence of chronic kidney disease: the Tehran thyroid study (TTS)

BACKGROUND

Evidence regarding the relationship between thyroid hormone levels within the normal range and the incidence of chronic kidney disease (CKD) in adults is scarce. This study aimed to identify the association between thyrotropin (TSH) and free thyroxine (FT4) levels with the incidence of CKD in a large cohort study over long-term follow-up.

METHODS

This prospective cohort study, with an 18-year follow-up, included 4118 adults without CKD from the Tehran thyroid Study (TTS). Participants were categorized by tertiles of normal TSH levels (low-normal, middle-normal, and high-normal) and abnormal TSH. The study outcome was incident CKD, defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2. Multivariable Cox proportional hazard models were used to estimate hazard ratios (HRs) for CKD incidence based on thyroid hormone levels.

RESULTS

The HR for CKD development was 1.08 (95%CI: 1.01-1.15) per 1 SD increase in the TSH levels. Compared with participants with low-normal TSH levels, those with high-normal (HR:1.37; 95%CI: 1.03-1.84) and abnormal TSH (HR:1.24; 95%CI: 1.05-1.46) had a significantly higher risk of developing CKD. In subgroup analyses, the association between TSH level and CKD was significant in participants younger than 60 years, females, non-obese, non-smokers, and those without diabetes and hypertension. No association was observed between FT4 levels and incident CKD (HR: 0.92; 95%CI: 0.79-1.09). However, a significant association was observed between FT4 levels within the normal range and CKD development in those younger than 60 years old (HR: 0.77; 95% CI: 0.61-0.98).

CONCLUSION

Increased TSH levels, even within the normal range, linearly increased the risk of CKD even after adjustment for important risk factors. As a result, TSH may potentially be an independent risk factor for incident CKD.

Thyroid disease in ANCA-associated vasculitis: a clinical and epidemiological study

OBJECTIVES

To describe clinical and laboratory characteristics and outcomes in patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and thyroid disease (TD). We also aimed to calculate incidence and identify predictors of TD in two large cohorts of patients with AAV.

METHODS

The study comprised 644 patients with AAV in a population-based cohort from southern Sweden (n=325) and a cohort from a specialised vasculitis centre in Cambridge, UK (n=319). Diagnosis and classification of AAV and TD were confirmed by medical record review. Person-years (PY) of follow-up were calculated from AAV diagnosis to the earliest of TD, death or the end of study. Cox-regression analysis was employed to study predictors of TD.

RESULTS

At AAV diagnosis, 100 individuals (15.5%, 77 females) had TD, 59 had myeloperoxidase (MPO)-ANCA+ and 34 had proteinase-3 (PR3)-ANCA+. Patients with TD tended to have lower C reactive protein, lower haemoglobin and fewer constitutional symptoms. Survival and renal survival was greater in those patients with AAV with pre-existing TD. During 4522 PY of follow-up, a further 29 subjects developed TD, yielding an incidence rate of 641/100 000 PY. No analysed factor predicted de novo TD in AAV. The prevalence of TD among patients with AAV in southern Sweden was 18%.

CONCLUSION

TD is a common comorbidity in AAV, affecting nearly one in five. While TD diagnosis is more common in females and MPO-ANCA+, these factors do not predict de novo TD after initiation of AAV treatment, necessitating monitoring of all patients with AAV with respect to this comorbidity.

Do not forget the kidney in graves' disease

PURPOSE

To investigate the prevalence of microalbuminuria and factors associated with microalbuminuria in Graves' Disease (GD).

METHODS

This cross-sectional and single-center study included 99 patients with GD and 47 healthy controls (HC). Exclusion criteria such as active infection, uncontrolled diabetes, and chronic kidney disease were applied to the participants. The participants' clinical findings, comorbidities, drug use, laboratory tests, and thyroid antibody levels were recorded. Spot urine samples were collected and stored at - 80 ℃ to analyze the presence of microalbuminuria.

RESULTS

The prevalence of microalbuminuria in patients with GD was 12.1%. The median microalbumin/creatinine ratio in spot urine (UACR) in patients with GD (9.49 mg/g [5.09-18.10]) was higher than in the HC group (7.99 mg/g [3.48-12.88], p = 0.033). UACR was correlated with thyroid-stimulating hormone receptor antibody (TRAb), thyroid-stimulating hormone (TSH), and free triiodothyronine (FT3) levels (p = 0.020, p = 0.006, p = 0.009 respectively). In the regression analysis, only the relationship between TRAb level and UACR remained (p = 0.040).

CONCLUSION

This study demonstrates an increased prevalence of microalbuminuria in patients with GD. There was a significant correlation between microalbuminuria and TRAb level in patients with GD. This relationship suggests that one of the underlying mechanisms of microalbuminuria seen in patients with GD may be autoimmunity.

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.

Low Circulating Free Triiodothyronine Levels are Associated with the Progression of Diabetic Nephropathy in Patients with Type 2 Diabetes

Background

Diabetic Nephropathy (DN) is one of the most typical causes of end-stage renal disease and thyroid hormone exerts effects on the kidney. There are few reports on the role of thyroid hormone in the progression of DN. We aimed to assess the relationship between thyroid hormone and DN.

Methods

In this cross-sectional study, 400 patients with type 2 diabetes (T2D) (aged between 35 and 70 years) were divided into two groups T2D control and DN group according to albumin creatinine ratio (ACR). Clinical biochemistry parameters were measured using the Rx Daytona chemistry analyzer and thyroid hormone levels (TT4, TT3, TSH, FT4, and FT3) using the Evidence Biochip analyzer. To assess the relationship between thyroid hormone and DN, multiple logistic regression models were developed.

Results

Serum FT4 and FT3 levels were significantly lower in DN compared to T2D controls (p<0.05). Thyroid hormone levels tend to decrease with the progression of DN. In unadjusted and adjusted logistic regression models, FT3 levels were negatively associated with odds of having DN (OR=0.28, CI=0.128-0.616, p=0.002).

Conclusion

The free triiodothyronine level was negatively associated with the progression of DN. Further longitudinal studies are required to assess the cause of thyroid hormone differences.

Association Between Subclinical Thyroid Dysfunction and Fracture Risk

IMPORTANCE

Clinical hyperthyroidism accelerates bone resorption without compensatory bone formation, reducing bone density and increasing the risk of fracture. The association between subclinical hyperthyroidism and fracture risk is less clear.

OBJECTIVE

To investigate the association of endogenous subclinical thyroid dysfunction and fracture risk, independent of clinical confounders.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included 10 946 participants from the Atherosclerosis Risk in Communities Study, an ongoing prospective cohort study of community-dwelling individuals conducted from 1987-1989 through December 31, 2019, in Washington County, Maryland; Forsyth County, North Carolina; Jackson, Mississippi; and the suburbs of Minneapolis, Minnesota. Participants were not taking thyroid medications and had no history of fractures.

EXPOSURES

Thyrotropin and free thyroxine levels were measured at visit 2 (1990-1992). Subclinical hyperthyroidism was defined as a thyrotropin level lower than 0.56 mIU/L, subclinical hypothyroidism as a thyrotropin level higher than 5.1 mIU/L, and euthyroidism as a thyrotropin level of 0.56 to 5.1 mIU/L, with normal free thyroxine levels from 0.85 to 1.4 ng/dL.

MAIN OUTCOMES AND MEASURES

Incident fracture was ascertained using hospitalization discharge codes through 2019 and linkage to inpatient and outpatient Medicare claims through 2018.

RESULTS

Of 10 946 participants (54.3% women; mean [SD] age, 57 [5.7] years), 93.0% had euthyroidism, 2.6% had subclinical hyperthyroidism, and 4.4% had subclinical hypothyroidism. During a median follow-up of 21 years (IQR, 13.0-27.3 years), there were 3556 incident fractures (167.1 per 10 000 person-years). The adjusted hazard ratios of fracture were 1.34 (95% CI, 1.09-1.65) for those with subclinical hyperthyroidism and 0.90 (95% CI, 0.77-1.05) for those with subclinical hypothyroidism compared with individuals with euthyroidism. Among those with normal free thyroxine levels, thyrotropin levels in the lower-than-normal range were significantly associated with higher fracture-related hospitalization risk; fracture risk was greater among individuals with thyrotropin concentrations below 0.56 mIU/L.

CONCLUSIONS AND RELEVANCE

This community-based cohort study suggests that subclinical hyperthyroidism was an independent risk factor associated with fracture. The increased risk for fracture among individuals with a thyrotropin level lower than 0.56 mIU/L highlights a potential role for more aggressive screening and monitoring of patients with subclinical hyperthyroidism to prevent bone mineral disease.

The association between hypothyroidism and proteinuria in patients with chronic kidney disease: a cross-sectional study

Hypothyroidism is known to be correlated with kidney function and nephrotic range proteinuria. However, it is uncertain whether non-nephrotic proteinuria is associated with hypothyroidism. This study aimed to evaluate the association of proteinuria and hypothyroidism in chronic kidney disease (CKD) patients. We conducted a cross-sectional study composed of 421 CKD patients in a single hospital with measurements of 24-h urine protein excretion (UP) and thyroid function tests. Spearman correlation analysis revealed that 24-h Cr clearance (24hrCcr) was positively (r = 0.273, p < 0.001) and UP was negatively (r = - 0.207, p < 0.001) correlated with free triiodothyronine. Frequency distribution analysis stratified by CKD stage and UP for hypothyroidism revealed that the prevalence of hypothyroidism was higher among participants with higher CKD stage and nephrotic range proteinuria. Multivariate logistic regression analysis revealed that 24hrCcr and UP were significantly correlated with hypothyroidism (24hrCcr/10 mL/min decrease: odds ratio [OR], 1.29; 95% confidence interval [CI], 1.18-1.41; UP/1 g increase: OR, 1.10; 95% CI, 1.03-1.17). In addition, nephrotic range proteinuria, but not moderate UP (UP: 1.5-3.49 g/day), was significantly correlated with hypothyroidism compared to UP < 0.5 g/day. In summary, decreased kidney function and nephrotic range proteinuria, not non-nephrotic proteinuria, are independently associated with the hypothyroidism.

Thyroid function and age-related decline in kidney function in older Chinese adults: a cross-sectional study

Background

Thyroid function may be a factor affecting kidney function in the general population. Kidney and thyroid function vary with age; therefore, the association between thyroid function and decreased kidney function in older adults may be different from that in younger adults and remains controversial. This study aimed to estimate the association between normal-range thyroid function and age-related decline in kidney function in older Chinese adults.

Methods

A total of 15,653 adults, of whom 23.2% (N = 3624) were older adults (age≧65 years), were collected at the Health Management Center of the First Affiliated Hospital of Nanjing Medical University from January 2018 to January 2020. Basic demographic information was collected by a physician-administered questionnaire. The estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI formula. Trends in thyroid function with age were shown by means of free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH) in subgroups every ten years. The association between kidney function and thyroid function was estimated by multiple linear regression using β value and by multivariable logistic regression models using odds ratios (OR) after adjusting for age, gender, body mass index, and serum urine acid.

Results

In the older population, TSH tended to increase with age and FT3 tended to decrease, whereas FT4 was relatively stable. eGFR decreased significantly with increasing TSH (β = -0.081) and decreasing FT3 (β = 0.083) concentrations. Compared with those in the lowest quartile of FT3 (3.10–4.47 pmol/L), the prevalence of eGFR < 75 ml/min/1.73m² decreased significantly by 22.0% for those with FT3 of 4.47–4.81 pmol/L, 27.6% for those with FT3 of 4.82–5.20 pmol/L, and 34.9% for those with FT3 of 5.21–6.8 pmol/L in older individuals (P for trend < .001). The OR was 1.315 (P: 0.025) in subjects with high-normal TSH, using low-normal TSH as a reference. The prevalence of reduced kidney function was not significantly associated with FT4 within the reference range. Similar results were found in association between the prevalence of eGFR < 60 ml/min/1.73m² and thyroid function.

Conclusions

This study demonstrated a significant association between kidney function and thyroid function, particularly FT3, in the older population. Clinicians may need to pay more attention to the assessment and follow-up of kidney function in older individuals with low-normal FT3 and high-normal TSH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02904-z.

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.

Evaluation of the Thyroid Characteristics and Correlated Factors in Hospitalized Patients with Newly Diagnosed Type 2 Diabetes

BACKGROUND

Diabetes mellitus (DM) and thyroid dysfunction (TD) are two closely associated disorders. The objective of the present study was to investigate the thyroid status and the relationships between thyroid hormones, diabetic complications and metabolic parameters in hospitalized patients with newly diagnosed type 2 DM (T2DM).

METHODS

This was an observational cross-sectional study, conducting on 340 patients with newly diagnosed T2DM who were admitted to ward of endocrinology department and 120 matched individuals without diabetes. Anthropometric, clinical and biochemical data were collected. Spearman correlation coefficients were calculated to evaluate the correlations between thyroid hormones and other variables. Factors associated with diabetic nephropathy (DN) was analyzed with multivariate logistic regression.

RESULTS

Levels of free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone (TSH) were significantly lower in patients with T2DM as compared to control group without diabetes. The prevalence of TD was 21.2% in patients with diabetes, higher than that in controls (4.2%). The low T3 syndrome was the most frequent TD, shown in 14.7% of patients. The presence of diabetic complications DN, diabetic ketosis or ketoacidosis), metabolic and demographic factors, including age, glycemic control and insulin resistance were factors significantly associated with levels of thyroid hormones. FT3 level was inversely correlated with the level of urinary total protein (mg/24h) and the presence of DN. Multivariate analysis indicated low FT3 level as a strong independent risk factor (OR = 0.364, P = 0.001) for DN.

CONCLUSION

TD is not rarely seen in hospitalized patients with newly diagnosed T2DM. Diabetic complications and diabetes-related metabolic and demographic factors are related to thyroid hormone levels. Decreased FT3 is strongly correlated with the presence of DN.

Gender and Age-Specific Differences in the Association of Thyroid Function and Hyperuricemia in Chinese: A Cross-Sectional Study

OBJECTIVE

We aimed to explore gender and age-specific influences on the association between thyroid function and hyperuricemia (HUA) in a large Chinese population.

METHODS

A total of 19,013 individuals (10,563 males and 8,450 females) were recruited. The association between HUA and thyroid function was analyzed by multivariate logistic regression, and the analyses were stratified by gender and age. Thyroid function subgroups were determined in 2 methods including thyroid status and thyroid-stimulating hormone (TSH) quartiles.

RESULTS

Overall prevalence of serum uric acid (SUA) and HUA was significantly higher in males, while TSH value and thyroid dysfunction were higher in females. Increasing trends of the TSH level in both genders as well as HUA prevalence in females were found positively along with aging. However, males showed a reduced trend in HUA risk negatively with aging. Our population showed that the risk of developing HUA in hyperthyroidism, normal euthyroidism, mild hypothyroidism, and overt hypothyroidism subgroups had adjusted ORs of 0.634, 1.229, 1.370, and 1.408, respectively, in males. Subjects in females showed a similar increased risk of HUA with ORs of 0.770, 1.198, 1.256, and 1.458, respectively. Similar tendency was observed in TSH quartiles; the above two models showed significantly higher risk of HUA in the high TSH group of males, but not of females. Aging was a significant risk factor for HUA, particularly in older females after adjusting for TSH.

CONCLUSION

The risk of HUA was positively associated with an elevation in TSH levels in both genders irrespective of age, indicating the protective effects of low TSH on HUA. Males with high TSH value were more vulnerable to suffer significant risk of HUA.

The Correlation Between Low Serum T3 Levels and All-Cause and Cardiovascular Mortality in Peritoneal Dialysis Patients

Objective

This study is to investigate the correlation between serum triiodothyronine (T3) levels and all-cause and cardiovascular mortality in PD patients.

Methods

A total of 376 end-stage renal disease (ESRD) patients who started maintenance PD treatment in the Department of Nephrology in our hospital and stable treatment for ≥3 months were selected, and the total T3 (TT3) and free T3 (FT3) levels were determined. Among them, 168 cases with FT3 <3.5 pmol/L and/or TT3 <0.92 nmol/L were divided into the low serum T3 level group, and the remaining 208 cases were divided into normal serum T3 level group. The Cox survival analysis method was used to analyze the correlation between low serum T3 levels and all-cause and cardiovascular mortality in PD patient.

Results

Compared with the normal serum T3 level group, patients with low serum T3 levels had higher systolic blood pressure and a higher proportion of heart disease, and lower levels of total T4, free T4, hemoglobin, serum albumin, blood calcium, serum total bilirubin, alanine aminotransferase, and 24-h urine volume (all P < 0.05). Binary Logistic regression analysis showed that heart disease (P = 0.003, OR: 2.628, 95% CI: 1.382–4.997) and high TT4 level (P < 0.001, OR: 0.968, 95% CI: 0.956–0.979) were related to low serum T3 levels in PD patients. Multivariate Cox regression analysis showed that low serum FT3 level was an independent risk factor for all-cause death in PD patients (HR = 0.633, 95% CI = 0.431–0.930; P < 0.020).

Conclusion

Low serum T3 levels in PD patients were associated with heart disease and TT4 levels. Low serum FT3 levels were associated with the risk of all-cause death in PD patients.

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.

Thyroid function, renal events and mortality in chronic kidney disease patients: the German Chronic Kidney Disease study

BACKGROUND

Hypothyroidism and low free triiodothyronine (FT3) syndrome [low FT3 levels with normal thyroid-stimulating hormone (TSH)] have been associated with reduced kidney function cross-sectionally in chronic kidney disease (CKD) patients with severely reduced estimated glomerular filtration rate (eGFR) or end-stage kidney disease (ESKD). Results on the prospective effects of impaired thyroid function on renal events and mortality for patients with severely reduced eGFR or from population-based cohorts are conflicting. Here we evaluated the association between thyroid and kidney function with eGFR (cross-sectionally) as well as renal events and mortality (prospectively) in a large, prospective cohort of CKD patients with mild to moderately reduced kidney function.

METHODS

Thyroid markers were measured among CKD patients from the German Chronic Kidney Disease study. Incident renal endpoints (combined ESKD, acute kidney injury and renal death) and all-cause mortality were abstracted from hospital records and death certificates. Time to first event analysis of complete data from baseline to the 4-year follow-up (median follow-up time 4.04 years) of 4600 patients was conducted. Multivariable linear regression and Cox proportional hazards models were fitted for single and combined continuous thyroid markers [TSH, free thyroxine (FT4), FT3] and thyroid status.

RESULTS

Cross-sectionally, the presence of low-FT3 syndrome showed a significant inverse association with eGFR and continuous FT3 levels alone showed a significant positive association with eGFR; in combination with FT4 and TSH, FT3 levels also showed a positive association and FT4 levels showed a negative association with eGFR. Prospectively, higher FT4 and lower FT3 levels were significantly associated with a higher risk of all-cause mortality (N events = 297). Per picomole per litre higher FT3 levels the risk of reaching the composite renal endpoint was 0.73-fold lower (95% confidence interval 0.65-0.82; N events = 615). Compared with euthyroid patients, patients with low-FT3 syndrome had a 2.2-fold higher risk and patients with hypothyroidism had a 1.6-fold higher risk of experiencing the composite renal endpoint.

CONCLUSIONS

Patients with mild to moderate CKD suffering from thyroid function abnormalities are at an increased risk of adverse renal events and all-cause mortality over time.

The Interplay Between Thyroid Dysfunction and Kidney Disease

Hypothyroidism is a highly prevalent endocrine complication in chronic kidney disease (CKD) patients. A large body of evidence has shown that there is a bidirectional relationship between thyroid dysfunction and kidney disease, yet there are many remaining gaps in knowledge in regards to the clinical management of CKD patients with hypothyroidism, including those receiving hemodialysis and peritoneal dialysis. Given that hypothyroidism has been associated with many deleterious outcomes including a higher risk of (1) mortality, (2) cardiovascular disease, (3) impaired health-related quality of life, and (4) altered body composition in both non-CKD and CKD patients, future research is needed to establish the appropriate screening, diagnosis, and treatment approaches in these populations.

A Polymorphism in the Gene Encoding the Insulin Receptor Binding Protein ENPP-1 Is Associated with Decreased Glomerular Filtration Rate in an Under-Investigated Indigenous African Population

INTRODUCTION

The C allele of the ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP-1) rs1044498 polymorphism has previously been associated with increased binding of ENPP-1 to the insulin receptor (IR), resulting in decreased IR signalling and enhanced insulin resistance. It has also been associated with reduced kidney function in participants with diabetes of predominantly European and Asian descent. The association of this polymorphism with kidney disease in healthy Black South African participants has yet to be ascertained.

OBJECTIVE

This study, therefore, aimed to determine whether the K121Q polymorphism is associated with estimated glomerular filtration rate (eGFR) in a Black South African cohort.

METHODS

Black South African participants (n = 348) from an existing cohort with known eGFR levels were genotyped for the K121Q polymorphism using PCR-RFLP and assessed for any statistical association between genotype and kidney function.

RESULTS

Individuals with the A allele had significantly lower eGFR levels than individuals with the CC genotype (86.52 ± 18.95 vs. 93.29 ± 23.55 mL/min; p = 0.022). The association of the A allele with lower eGFR levels remained after controlling for sex, blood pressure, insulin resistance, age, smoking, thyroid-stimulating hormone, insulin-like growth factor-1, and BMI (R2 = 0.030, p < 0.001).

CONCLUSION

The rs1044498 A allele was significantly associated with lower eGFR levels in a cohort of apparently healthy Black South Africans, through an unknown mechanism that was independent of insulin resistance. It is possible that the rs1044498 polymorphism affects kidney function by altering the role of ENPP-1 in endothelial wound healing, podocyte signalling, or oxidative stress. Thus, the presence of this polymorphism may predispose individuals to a greater risk of CKD even in the absence of diabetes.

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.

Association of Subclinical Thyroid Dysfunction with Chronic Kidney Disease: A Systematic Review and Meta-analysis

Background: The association of subclinical thyroid dysfunction (SCTD) with chronic kidney disease (CKD) among community population remains inconclusive. Our aim was to evaluate the association between SCTD and the risk of CKD by conducting a meta-analysis.Methods: Multiple databases were searched to identify studies on the association between SCTD and risk of CKD, up to October 2018. Relevant information for analysis was extracted. A random-effects model was used to calculate the pooled risk estimate.Results: Eight articles were included in this meta-analysis, with three cohort and five cross-sectional studies. The pooled odds ratio (OR) of subclinical hypothyroidism for CKD was 1.37 (95% CI: 1.13-1.67, P = .000, n = 8) in a multivariable-adjusted model. A significant association was observed in subgroup younger than 70 years (OR = 1.40, 95% CI: 1.09-1.79, P = .000, n = 6), but not in subgroup older than 70 years (OR = 1.28, 95% CI: 0.89-1.83, P = .186, n = 2). For subclinical hyperthyroidism, the summary OR was 1.16 (95%CI: 0.97-1.39, P = .115, n = 5) and subgroup analyses by age and study design did not alter the results significantly.Conclusions: Our findings demonstrated that subclinical hypothyroidism was significantly associated with a higher risk of CKD independent of some conventional risk factors among community population and age might have modifying effects on the association.

Thyroid Parameters and Kidney Disorder in Type 2 Diabetes: Results from the METAL Study

OBJECTIVE

Diabetic kidney disease is one of the most common microvascular complications of diabetes mellitus. We aimed to analyze the association of thyroid parameters with kidney disorders, especially in euthyroid participants.

METHODS

The data were obtained from a cross-sectional study, the METAL study. Thyroid parameters, including thyroid-stimulating hormone (TSH), free triiodothyronine (FT₃), free thyroxine (FT₄), triiodothyronine (T₃), thyroxin (T₄), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb), of 4136 participants with type 2 diabetes were measured. Two structure parameters of thyroid homeostasis, including the sum activity of step-up deiodinases (SPINA-G_D) and thyroid secretory capacity (SPINA-G_T), and two pituitary thyrotropic function indices, including Jostel's TSH index (TSHI) and the thyrotroph thyroid hormone resistance index (TTSI), were also calculated. Kidney disorders were described according to the presence of reduced estimated glomerular filtration rate (eGFR) and/or higher urinary albumin to creatinine ratio (UACR).

RESULTS

The prevalence of kidney disorders increased with decreasing FT₃ or T₃ and increasing FT₄ or T₄ quartile levels (all P < 0.05). After full adjustment, linear regression showed that UACR levels were negatively associated with FT₃ and T₃ (P < 0.001). In addition, eGFR was positively associated with FT₃ and T₃ and was negatively associated with TSH and FT₄ levels and TgAb positivity (all P < 0.05). By using binary logistic regression, higher TSH and FT₄ and lower FT₃ and T₃ were associated with kidney disorders (all P < 0.05). Similar results were seen in sensitivity analyses, which were performed in 3035 euthyroid diabetic participants; however, TSH was no longer related to them. The area under the receiver operating characteristic curve (AUROC) of lower FT₃ for existing kidney disorder was greater than that for any other thyroid hormones (all P < 0.001). The cutoff value of FT₃ for reduced eGFR was 4.39 pmol/L. Regarding thyroid homeostasis parameters, SPINA-G_D was negatively associated with three statuses of kidney disorders, and TSHI and TTSI were positively associated with reduced eGFR (all P < 0.05).

CONCLUSIONS

Among patients with type 2 diabetes, elevated TSH and FT₄ (or T₄), lower FT₃ (or T₃), TgAb positivity, lower SPINA-G_D, and higher TSHI and TTSI were associated with kidney disorders. The lower FT₃, even within the normal range (<4.38 pmol/L), may be the factor most related to reduced eGFR compared with other thyroid hormones in diabetic patients.

Prevalence and Risk Factors of Thyroid Dysfunction in Older Adults in the Community

Prevalence estimates and evidence informing treatment targets for thyroid dysfunction largely come from studies of middle-aged adults. We conducted a cross-sectional analysis to determine the prevalence of thyroid dysfunction and risk factors for abnormal thyroid tests in participants aged ≥65 in the Atherosclerosis Risk in Communities (ARIC) study (N = 5,392). We measured serum concentrations of triiodothyronine (T3), free thyroxine (FT4), thyroid peroxidase antibody (Anti-TPO), and thyroid stimulating hormone (TSH). In this population (58% women, 22% black), 17% reported medication use for thyroid dysfunction. Among those not on treatment, the prevalence of overt and subclinical hypothyroidism was 0.82% and 6.06%, respectively. Overt and subclinical hyperthyroidism affected 0.26% and 0.78%, respectively. Multivariable adjusted TSH, FT4 and T3 levels were 25%, 1.3% and 3.9% lower in blacks compared to whites, respectively. Men were less likely to be anti-TPO positive compared to women (p < 0.001). Former and never smoking were associated with lower T3 and FT4 levels compared to current smoking. The prevalence of thyroid dysfunction in older adults is nearly 25%. Multiple illnesses can interact to contribute to declines in health. Additional attention to thyroid dysfunction and screening in this age group is recommended.

Functional Abnormalities and Thyroid Nodules in Patients with End-stage Renal Disease

BACKGROUND/AIM

Clinical and subclinical hypothyroidism is more common in patients with end-stage renal disease (ESRD) than in the general population. Patients with ESRD with hypothyroidism are more susceptible to cardiovascular disease, with an increased risk of mortality than those with normal thyroid function. Moreover, these patients have higher incidence of benign and malignant nodules.

PATIENTS AND METHODS

This was a retrospective study on 2,147 patients with ESRD on the renal transplant waiting list between 2000 and 2015 aimed at identifying the presence of hypothyroidism and associated variables.

RESULTS

Hypothyroidism was detected in 437/2,147 (20.3%) patients, 289 of them having the subclinical form. Cardiovascular disease and older age were significantly associated with hypothyroidism, and autosomal polycystic kidney disease was correlated to goiter (p<0.001).

CONCLUSION

Thyroid abnormalities, particularly hypothyroidism with nodules, should be investigated in patients with ESRD on a waiting list for renal transplant to control cardiovascular complications and cancer risk.

ROSACEA IS ASSOCIATED WITH THYROID AUTOIMMUNITY: A CASE CONTROL STUDY

BACKGROUND AND AIMS

There are numerous intrinsic and extrinsic factors associated with the pathophysiology of rosacea, including immune dysregulation. The aim of this study is to determine the relationship between rosacea and thyroid autoimmunity.

METHODS

Seventy-two patients with rosacea and 62 rosacea-free control subjects were included in the study. Serum free triiodothyronine (fT3), free thyroxine (fT4), thyrotropin releasing hormone (TSH), antithyroidperoxidase antibody (ATPO), antithyroglobulin (anti-Tg), prolactin, dehydroepiandrosterone sulfate (DHEAS), basal cortisol, serum CRP concentrations and erythrocyte sedimentation rate were measured.

RESULTS

The number of the cases with high levels of CRP, anti-M and prolactin in rosacea group were significantly higher than the controls (p<0.05), there was no significant difference according to other parameters in both groups (p>0.05). There was no significant difference according to the presence of a thyroid disease in both groups (p>0.05). The decrease in the CRP parameter in patients with the disease duration of 1-5 years was found to be statistically significant (βCRP=-0.251, pCRP<0.05). There was no statistically significant difference according to disease severity or disease duration (p>0.05).

CONCLUSIONS

Rosacea may be associated with high thyroid autoantibodies, prolactin and CRP levels, in which immune-endocrine interactions are important.

Circulating antithyroid antibodies contribute to the decrease of glomerular filtration rate in lithium-treated patients: a longitudinal study

Background

Concerns about the adverse effects of long-term treatment with lithium include reduced renal function. In the present study, we examined comorbidities which may be associated with chronic kidney disease in a cohort of patients treated with lithium for up to 41 years.

Methods

We studied 394 patients who were treated with lithium for ≥ 5 years. The potential role of comorbidities (diabetes, concurrent antihypertensive medication, treatment with l-thyroxine, and presence of antithyroid peroxidase/microsomes, anti-thyroglobulin, and/or anti-thyrotropin-receptor antibodies) was analysed. We focused on the categories of patients with an estimated glomerular filtration rate (eGFR) lower than 60 or 45 mL/min/1.73 m² as calculated from serum creatinine according to the Modification of Diet in Renal Disease Study Group. We applied multivariate regression analysis and Cox survival analysis to study the effects exerted by sex, age, duration of lithium treatment, and comorbidities using eGFR categories as the dependent variable. Kaplan–Meier curves were generated to measure the time to decline to an eGFR lower than 45 mL/min/1.73 m² in patients with positive or negative thyroid antibodies.

Results

Age was associated with a decline to an eGFR lower than 60 mL/min/1.73 m² after controlling for sex, duration of lithium treatment, and comorbidities. Circulating thyroid antibodies were associated with a decline to an eGFR lower than 45 mL/min/1.73 m².

Conclusions

The present study is the first to suggest a potential role of circulating thyroid antibodies in the severe decline of eGFR in lithium-treated patients.

Glomerular filtration rate is associated with free triiodothyronine in euthyroid subjects: Comparison between various equations to estimate renal function and creatinine clearance

BACKGROUND

Effects of variations in thyroid function within the euthyroid range on renal function are unclear. Cystatin C-based equations to estimate glomerular filtration rate (GFR) are currently advocated for mortality and renal risk prediction. However, the applicability of cystatin C-based equations is discouraged in patients with overt thyroid dysfunction, since serum cystatin C and creatinine levels are oppositely affected by thyroid dysfunction. Here, we compared relationships of thyroid stimulating hormone (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) with various measures of kidney function in euthyroid subjects.

METHODS

Relationships of eGFR, based on creatinine (eGFRcrea), cystatin C (eGFRcysC), creatinine+cystatin C combined (eGFRcrea-cysC) and creatinine clearance (CrCl) with TSH, FT4 and FT3 were determined in 2180 euthyroid subjects (TSH, FT4 and FT3 all within the reference range; anti-thyroid peroxidase autoantibodies negative) who did not use thyroid hormones, anti-thyroid drugs, amiodarone or lithium carbonate.

RESULTS

In multivariable models including TSH, FT3 and FT4 together, eGFRcrea, eGFRcysC and eGFRcrea-cysC and CrCl were all positively related to FT3 (P≤0.001), translating into a 2.61 to 2.83mL/min/1.73m² increase in eGFR measures and a 3.92mL/min increase in CrCl per 1pmol/L increment in FT3. These relationships with FT3 remained taking account of relevant covariates.

CONCLUSIONS

In euthyroid subjects renal function is associated with thyroid function status, especially by serum FT3, irrespective of the eGFR equation applied. In the euthyroid state, cystatin C-based eGFR equations are appropriate to assess the relationship of renal function with variation in thyroid function status.