Thyroid status and renal function in older persons in the general population

The Association Between Thyroid Hormones and Renal Function in Euthyroid Chinese Individuals: A Population-Based Cross-Sectional Study

Objective This population-based cross-sectional study aimed to investigate the association between thyroid hormones and renal function in euthyroid Chinese individuals, as the relationship between thyroid hormones and renal function in this population remains unclear. Methods A total of 661 participants were included in the study after excluding individuals with thyroid diseases, incomplete clinical measurements, or those taking medications affecting thyroid function. Participants were categorized into three groups based on serum thyroid hormone and antibody levels. The study adjusted for covariates and assessed the glomerular filtration rate (GFR) and urine albumin-to-creatinine ratio (ACR) in relation to thyroid hormone levels. Results After adjusting for covariates, the study found a significant increase in GFR in the middle and highest tertiles of free triiodothyronine (FT3) and the highest tertile of total triiodothyronine (TT3). Serum FT3 and TT3 levels were significantly associated with GFR. Additionally, the study observed a significantly lower GFR in the highest tertile of thyroid-stimulating hormone (TSH) compared to the lowest tertile. However, thyroid hormone and antibody levels were not associated with the ACR. Furthermore, the highest tertiles of TT3 and total thyroxine (TT4) were associated with a decreased risk of chronic kidney disease (CKD). Conclusion In our study among euthyroid Chinese individuals, we observed a significant association between thyroid function and GFR. Specifically, lower FT3, TT3, and higher TSH were associated with reduced GFR, indicating a potential role for thyroid hormones in maintaining renal function. Furthermore, lower levels of TT3 and TT4 were associated with an increased risk of CKD. These findings suggest a direct link between thyroid and renal function, even in euthyroid individuals, emphasizing the need for further investigation to elucidate the underlying mechanisms and potential therapeutic implications.

Increased risk of incident gout in patients with hyperthyroidism: a nationwide retrospective cohort study

Previous studies have reported that thyroid dysfunction is associated with increased serum uric acid levels; however, the relationship between hyperthyroidism and incidence of clinical manifestations of gout has not been fully investigated. Therefore, this study aimed to longitudinally investigate the risk of gout in patients with hyperthyroidism. This nationwide retrospective cohort study used data from the Korean National Health Claims Database. We included 76,494 patients with hyperthyroidism and 76,542 age- and sex-matched controls. A Cox proportional hazard regression model was used to adjust for potential confounders and estimate the risk of incident gout in patients with hyperthyroidism. During a mean follow-up of 9 years, incident gout developed in 3,655 (4.8%) patients with hyperthyroidism and 3251 (4.2%) controls. Hyperthyroidism was significantly associated with increased risk of incident gout [adjusted hazard ratio (HR), 1.12; 95% confidence interval (CI) 1.07-1.18], independent of baseline metabolic profiles. The median time from the diagnosis of hyperthyroidism to the development of gout was 6 years. When stratified by age and sex, the risk of gout was still significant in the < 50-year age group (HR: 1.2, 95% CI 1.12-1.29) and males (HR: 1.21, 95% CI 1.12-1.30), but not in the older age group (> 50 years) and females. Hyperthyroidism is an important risk factor for incident gout, particularly in younger age groups (< 50 years) and males. Our results highlight the importance of continuous screening for gout in patients with hyperthyroidism.

Impact of Thyroid Status on Incident Kidney Dysfunction and Chronic Kidney Disease Progression in a Nationally Representative Cohort

OBJECTIVE

To examine the relationship between thyroid status and incident kidney dysfunction/chronic kidney disease (CKD) progression.

PATIENTS AND METHODS

We examined incident thyroid status, ascertained by serum thyrotropin (TSH) levels measured from January 1, 2007, through December 31, 2018, among 4,152,830 patients from the Optum Labs Data Warehouse, containing deidentified retrospective administrative claims data from a large national health insurance plan and electronic health record data from a nationwide network of provider groups. Associations of thyroid status, categorized as hypothyroidism, euthyroidism, or hyperthyroidism (TSH levels >5.0, 0.5-5.0, and <0.5 mIU/L, respectively), with the composite end point of incident kidney dysfunction in patients without baseline kidney dysfunction and CKD progression in those with baseline CKD were examined using Cox models.

RESULTS

Patients with hypothyroidism and hyperthyroidism had higher risk of incident kidney dysfunction/CKD progression in expanded case-mix analyses (reference: euthyroidism): adjusted hazard ratios (aHRs) (95% CIs) were 1.37 (1.34 to 1.40) and 1.42 (1.39 to 1.45), respectively. Incrementally higher TSH levels in the upper reference range and TSH ranges for subclinical, mild overt, and overt hypothyroidism (≥3.0-5.0, >5.0-10.0, >10.0-20.0, and >20.0 mIU/L, respectively) were associated with increasingly higher risk of the composite end point (reference: TSH level, 0.5 to <3.0 mIU/L): aHRs (95% CIs) were 1.10 (1.09 to 1.11), 1.37 (1.34 to 1.40), 1.70 (1.59 to 1.83), and 1.70 (1.50 to 1.93), respectively. Incrementally lower TSH levels in the subclinical (<0.5 mIU/L) and overt (<0.1 mIU/L) hyperthyroid ranges were also associated with the composite end point: aHRs (95% CIs) were 1.44 (1.41 to 1.47) and 1.48 (1.39 to 1.59), respectively.

CONCLUSION

In a national cohort, TSH levels in the upper reference range or higher (≥3.0 mIU/L) and below the reference range (<0.5 mIU/L) were associated with incident kidney dysfunction/CKD progression.

The optimal healthy ranges of thyroid function defined by the risk of cardiovascular disease and mortality: systematic review and individual participant data meta-analysis

BACKGROUND

Reference intervals of thyroid-stimulating hormone (TSH) and free thyroxine (FT4) are statistically defined by the 2·5-97·5th percentiles, without accounting for potential risk of clinical outcomes. We aimed to define the optimal healthy ranges of TSH and FT4 based on the risk of cardiovascular disease and mortality.

METHODS

This systematic review and individual participant data (IPD) meta-analysis identified eligible prospective cohorts through the Thyroid Studies Collaboration, supplemented with a systematic search via Embase, MEDLINE (Ovid), Web of science, the Cochrane Central Register of Controlled Trials, and Google Scholar from Jan 1, 2011, to Feb 12, 2017 with an updated search to Oct 13, 2022 (cohorts found in the second search were not included in the IPD). We included cohorts that collected TSH or FT4, and cardiovascular outcomes or mortality for adults (aged ≥18 years). We excluded cohorts that included solely pregnant women, individuals with overt thyroid diseases, and individuals with cardiovascular disease. We contacted the study investigators of eligible cohorts to provide IPD on demographics, TSH, FT4, thyroid peroxidase antibodies, history of cardiovascular disease and risk factors, medication use, cardiovascular disease events, cardiovascular disease mortality, and all-cause mortality. The primary outcome was a composite outcome including cardiovascular disease events (coronary heart disease, stroke, and heart failure) and all-cause mortality. Secondary outcomes were the separate assessment of cardiovascular disease events, all-cause mortality, and cardiovascular disease mortality. We performed one-step (cohort-stratified Cox models) and two-step (random-effects models) meta-analyses adjusting for age, sex, smoking, systolic blood pressure, diabetes, and total cholesterol. The study was registered with PROSPERO, CRD42017057576.

FINDINGS

We identified 3935 studies, of which 53 cohorts fulfilled the inclusion criteria and 26 cohorts agreed to participate. We included IPD on 134 346 participants with a median age of 59 years (range 18-106) at baseline. There was a J-shaped association of FT4 with the composite outcome and secondary outcomes, with the 20th (median 13·5 pmol/L [IQR 11·2-13·9]) to 40th percentiles (median 14·8 pmol/L [12·3-15·0]) conveying the lowest risk. Compared with the 20-40th percentiles, the age-adjusted and sex-adjusted hazard ratio (HR) for FT4 in the 80-100th percentiles was 1·20 (95% CI 1·11-1·31) for the composite outcome, 1·34 (1·20-1·49) for all-cause mortality, 1·57 (1·31-1·89) for cardiovascular disease mortality, and 1·22 (1·11-1·33) for cardiovascular disease events. In individuals aged 70 years and older, the 10-year absolute risk of composite outcome increased over 5% for women with FT4 greater than the 85th percentile (median 17·6 pmol/L [IQR 15·0-18·3]), and men with FT4 greater than the 75th percentile (16·7 pmol/L [14·0-17·4]). Non-linear associations were identified for TSH, with the 60th (median 1·90 mIU/L [IQR 1·68-2·25]) to 80th percentiles (2·90 mIU/L [2·41-3·32]) associated with the lowest risk of cardiovascular disease and mortality. Compared with the 60-80th percentiles, the age-adjusted and sex-adjusted HR of TSH in the 0-20th percentiles was 1·07 (95% CI 1·02-1·12) for the composite outcome, 1·09 (1·05-1·14) for all-cause mortality, and 1·07 (0·99-1·16) for cardiovascular disease mortality.

INTERPRETATION

There was a J-shaped association of FT4 with cardiovascular disease and mortality. Low concentrations of TSH were associated with a higher risk of all-cause mortality and cardiovascular disease mortality. The 20-40th percentiles of FT4 and the 60-80th percentiles of TSH could represent the optimal healthy ranges of thyroid function based on the risk of cardiovascular disease and mortality, with more than 5% increase of 10-year composite risk identified for FT4 greater than the 85th percentile in women and men older than 70 years. We propose a feasible approach to establish the optimal healthy ranges of thyroid function, allowing for better identification of individuals with a higher risk of thyroid-related outcomes.

FUNDING

None.

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.

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.

A Study to Evaluate the Association Between Thyroid Function and Serum Potassium Level in Diagnosed Cases of Diabetic Nephropathy

Introduction Coexistence of diabetes mellitus and thyroid diseases is common. One of the main microvascular complications of diabetes is diabetic nephropathy (DN) and it is found to be the leading cause of chronic kidney disease. The aim of the present study was to assess the association between hypothyroidism and serum potassium levels in diabetic nephropathy patients. Materials and methods A cross-sectional study was conducted from March 2020 to January 2021. We enrolled 100 patients with DN along with 50 healthy controls belonging to the same localities. Serum potassium, creatinine, thyroid-stimulating hormone (TSH) and total triiodothyronine (T3) levels of all the cases were measured to establish the correlation of serum potassium along with each parameter separately. Results Serum potassium, creatinine, TSH levels were increased in all the cases of diabetic nephropathy showing positive correlations of serum potassium with serum TSH and serum creatinine levels with correlation coefficient values 0.71 and 0.7 respectively and serum T3 levels were decreased in all the cases significantly showing negative correlation with serum potassium levels with correlation coefficient value -0.34. Conclusion Estimation of serum TSH and T3 levels along with serum potassium levels is important and helpful in patients with diabetic renal disease. Changes in thyroid parameters like decreased TSH or increased T3 are significantly associated with deterioration in the severity of renal function in diabetic patients.

A long-term nationwide study on chronic kidney disease-related mortality in Italy: trends and associated comorbidity

BACKGROUND

Chronic kidney diseases (CKDs) represent a major public health concern worldwide with increasing incidence and prevalence. However, the epidemiological dimension of CKD in Italy is still under evaluation. By analyzing all the conditions reported on death certificates (multiple causes of death), we aimed to investigate the real burden of CKD mortality in Italy over 15 years and identify the main conditions contributing to death in association with CKD.

METHODS

Death certificates of all deaths occurring in Italy from 2003 to 2017 were analyzed. Certificates reporting CKD were identified as CKD-related deaths. CKD-related mortality was investigated through age-standardized mortality rates, by sex and age. Conditions associated with CKD were identified through an indicator (age-standardized proportion ratio) measuring the excess proportion (value > 1) of having such conditions mentioned in the death certificate with and without CKD.

RESULTS

From 2003 to 2017, multiple-cause-based CKD mortality rates increased by 60% in males and by 54% in females. The overall increase was mostly attributable to people aged 80 years or more. Several conditions were associated with CKD, the most relevant being diabetes (age-standardized proportion ratio = 2.2), obesity (2.1), systemic connective tissue disorders (2.3), anemia (2.7), and genitourinary system diseases (2.6).

CONCLUSIONS

Multiple-cause-of-death data revealed a significant increase in CKD-related mortality in recent years, providing a measure of the burden of CKD on overall mortality in Italy. Moreover, multiple cause analysis allowed to identify the main conditions contributing to death in association with CKD, which should be aggressively targeted by clinicians to prevent CKD adverse outcomes.

Subclinical hypothyroidism is independently associated with poor renal outcomes in patients with chronic kidney disease

PURPOSE

It remains unclear whether subclinical hypothyroidism (SCH) is associated with renal prognosis in patients with chronic kidney disease (CKD). Therefore, we prospectively investigated the association of SCH with renal outcomes in CKD.

METHODS

We conducted a prospective observational study of 480 euthyroid patients and 89 patients with SCH. The endpoints were defined as a composite of doubling of serum creatinine (SCr), end-stage renal disease (ESRD), or death, and a composite of doubling of SCr or ESRD was added as an alternative outcome. Logistic regression analyses were used to identify the factors associated with SCH. In addition, a Cox proportional hazards model was performed to determine whether SCH was associated with poor renal outcomes.

RESULTS

During a median follow-up period of 26.1 months, doubling of SCr, ESRD, or death and doubling of SCr or ESRD occurred in 244 and 213 patients, respectively. In univariable logistic regression analyses, SCH was significantly associated with older age, lower hemoglobin, higher proteinuria, lower estimated glomerular filtration rate (eGFR), and higher log B-type natriuretic peptide (BNP). Multivariable Cox analyses showed that SCH was associated with poorer renal outcomes after adjustment for covariates, including eGFR and log BNP [doubling of SCr, ESRD, or death: hazard ratio (HR) 1.61, 95% confidence interval (CI), 1.16-2.23; doubling of SCr or ESRD: HR 1.53, 95% CI 1.07-2.20], compared with euthyroidism.

CONCLUSIONS

In CKD, SCH is independently associated with poor renal outcomes, suggesting that screening for SCH might be needed to accurately predict renal prognosis.

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.

Association of Serum Thyroid Hormones with the Risk and Severity of Chronic Kidney Disease Among 3563 Chinese Adults

Background

Chronic kidney disease (CKD) is a global health problem with an increasing prevalence. We explored the association of serum thyroid hormones with the risk and severity of CKD among Chinese adults.

Material/Methods

This retrospective study involved 3563 participants. CKD was diagnosed according to the clinical practice guidelines of the 2012 Kidney Disease Improving Global Outcomes guidelines. Effect-size estimates are expressed as odds ratio (OR) and 95% confidence interval (CI).

Results

Given the strong magnitude of correlation, only 3 thyroid hormones were analyzed: free triiodothyronine (FT3), free thyroxin (FT4), and thyroid-stimulating hormone (TSH). After propensity score matching on age, sex, diabetes, and hypertension, per 0.2 pg/mL increase in FT3 was significantly associated with 35–38% reduced risk of CKD at stage 1–4, and per 0.3 ng/dL increase in FT4 was only significantly associated with 21% reduced risk of CKD at stage 5 (OR, 95% CI: 0.79, 0.69–0.89), and per 0.5 μIU/mL increment in TSH increased the risk of CKD stage 5 by 8% (1.08, 1.02–1.14). Importantly, 3 thyroid hormones acted interactively, particularly for the interaction between FT3 and FT4 in predicting CKD at stage 5 (OR, 95% CI: 1.81, 1.30–2.55 for high FT3-low FT4, 17.72, 7.18–43.74 for low FT3-high FT4, and 22.28, 9.68–51.30 for low FT3-low FT4).

Conclusions

Our findings indicate that serum FT3 can be used as an early-stage biomarker for CKD, and FT4 and TSH can be used as advanced-stage biomarkers among Chinese adults.

Association of thyroid status prior to transition to end-stage renal disease with early dialysis mortality

BACKGROUND

Advanced chronic kidney disease (CKD) patients, including those receiving dialysis, have a high prevalence of thyroid dysfunction. Although hypothyroidism is associated with higher death risk in end-stage renal disease (ESRD) patients, no studies have examined whether thyroid status in the pre-ESRD period impacts mortality after dialysis initiation.

METHODS

Among US veterans with CKD identified from the national Veterans Affairs database that transitioned to dialysis over the period from October 2007 to September 2011, we examined the association of pre-ESRD serum thyrotropin (TSH) levels averaged over the 1-year pre-dialysis ('prelude') period with all-cause mortality in the first year following dialysis initiation.

RESULTS

Among 15 335 patients in the 1-year prelude cohort, TSH levels >5.0 mIU/L were associated with higher mortality in expanded case-mix Cox models (reference: TSH 0.5-5.0 mIU/L): adjusted hazard ratio (aHR) [95% confidence interval (CI) 1.20 (1.07-1.33). Similar findings were observed for TSH >5.0 mIU/L and mortality in the 2- and 5-year cohorts: aHRs (95% CI) 1.11 (1.02-1.21) and 1.15 (1.07-1.24), respectively. Analyses of finer gradations of TSH in the 1-year prelude cohort demonstrated that incrementally higher levels >5.0 mIU/L were associated with increasingly higher mortality in expanded case-mix models (reference: TSH 0.5-3.0 mIU/L): aHRs (95% CI) 1.18 (1.04-1.33) and 1.28 (1.03-1.59) for TSH levels >5.0-10.0 mIU/L and >10.0 mIU/L, respectively. In the 2- and 5-year cohorts, mortality associations persisted most strongly for those with TSH >10.0 mIU/L, particularly after laboratory covariate adjustment.

CONCLUSIONS

Among new ESRD patients, there is a dose-dependent relationship between higher pre-ESRD TSH levels >5.0 mIU/L and post-ESRD mortality. Further studies are needed to determine the impact of TSH reduction with thyroid hormone supplementation in this population.

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.

RENAL FUNCTION AND PLASMA RENIN ACTIVITY AS POTENTIAL FACTORS CAUSING HYPERKALEMIA IN PATIENTS WITH THYROID CARCINOMA UNDERGOING THYROID HORMONE WITHDRAWAL FOR RADIOACTIVE IODINE THERAPY

Objective: Hypothyroidism is not commonly considered a cause of hyperkalemia. We previously reported that hyperkalemia was observed mainly in elderly patients treated with renin-angiotensin-aldosterone system (RAS) inhibitors when levothyroxine treatment was withdrawn for the thyroidectomized patients with thyroid carcinoma to undergo radioactive iodine treatment. Here, we investigated whether acute hypothyroidism causes hyperkalemia in patients who were not treated with RAS inhibitors. We also investigated factors influencing potassium metabolism in hypothyroid patients. Methods: We conducted a single-center, prospective cohort study of 46 Japanese patients with thyroid carcinoma undergoing levothyroxine withdrawal prior to radioiodine therapy. All patients were normokalemic before levothyroxine withdrawal. Blood samples were analyzed 3 times: before, and at 3 and 4 weeks after levothyroxine withdrawal. We investigated factors that may be associated with the elevation of serum potassium levels from a euthyroid state to a hypothyroid state. Results: None of the patients developed symptomatic hyperkalemia. The mean serum potassium level was significantly higher at 4 weeks after levothyroxine withdrawal compared to baseline. The serum sodium levels, the estimated glomerular filtration rate (eGFR), and the plasma renin activity (PRA) decreased significantly as hypothyroidism advanced. In contrast, the plasma levels of adrenocorticotropic hormone, cortisol, aldosterone, and antidiuretic hormone were not changed, while serum thyroid hormone decreased. At 4 weeks after their levothyroxine withdrawal, the patients' serum potassium values were significantly correlated with the eGFR and the PRA. Conclusion: Acute hypothyroidism can cause a significant increase in the serum potassium level, which may be associated with a decreased eGFR and decreased circulating RAS. Abbreviations: ACTH = adrenocorticotropic hormone; ADH = antidiuretic hormone; ATPase = adenosine triphosphatase; eGFR = estimated glomerular filtration rate; HbA1c = glycated hemoglobin; K⁺ = potassium; Na⁺ = sodium; PRA = plasma renin activity; RAS = renin-angiotensin-aldosterone system; T4 = thyroxine; TSH = thyroid-stimulating hormone.

Low thyroid function is not associated with an accelerated deterioration in renal function

BACKGROUND

Chronic kidney disease (CKD) is frequently accompanied by thyroid hormone dysfunction. It is currently unclear whether these alterations are the cause or consequence of CKD. This study aimed at studying the effect of thyroid hormone alterations on renal function in cross-sectional and longitudinal analyses in individuals from all adult age groups.

METHODS

Individual participant data (IPD) from 16 independent cohorts having measured thyroid stimulating hormone, free thyroxine levels and creatinine levels were included. Thyroid hormone status was defined using clinical cut-off values. Estimated glomerular filtration rates (eGFR) were calculated by means of the four-variable Modification of Diet in Renal Disease (MDRD) formula. For this IPD meta-analysis, eGFR at baseline and eGFR change during follow-up were computed by fitting linear regression models and linear mixed models in each cohort separately. Effect estimates were pooled using random effects models.

RESULTS

A total of 72 856 individuals from 16 different cohorts were included. At baseline, individuals with overt hypothyroidism (n = 704) and subclinical hypothyroidism (n = 3356) had a average (95% confidence interval) -4.07 (-6.37 to -1.78) and -2.40 (-3.78 to -1.02) mL/min/1.73 m2 lower eGFR as compared with euthyroid subjects (n = 66 542). In (subclinical) hyperthyroid subjects (n = 2254), average eGFR was 3.01 (1.50-4.52) mL/min/1.73 m2 higher. During 329 713 patient years of follow-up, eGFR did not decline more rapidly in individuals with low thyroid function compared with individuals with normal thyroid function.

CONCLUSIONS

Low thyroid function is not associated with a deterioration of renal function. The cross-sectional association may be explained by renal dysfunction causing thyroid hormone alterations.

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.

Gender impact on the correlations between Graves' hyperthyroidism and hyperuricemia in Chinese

OBJECTIVE

An increased level of serum uric acid (SUA) can be observed in patients with hypothyroidism. Nonetheless, data on the relationship between hyperuricemia and hyperthyroidism was still controversial. Thus, we aimed to analyze the association between Graves' hyperthyroidism and hyperuricemia in Chinese men and women.

METHODS

We recruited 103 male and 254 female patients with Graves' hyperthyroidism, as well as the same number of control subjects. Anthropometric measurements and fasting blood tests were collected and analyzed statistically by binary logistic regressions to determine the risk of developing hyperuricemia in hyperthyroidism.

RESULTS

SUA levels in males were significantly higher than that in females in both patients and controls. SUA levels were also significantly increased in hyperthyroid patients compared to in controls in both genders. The incidence of hyperuricemia rose significantly in subjects with hyperthyroidism with a higher prevalence in males than in females. SUA was negatively correlated with age and fasting glucose in male hyperthyroid patients, while it was positively correlated with body height, body weight, free triiodothyronine, and free thyroxine in female patients. Hyperthyroidism was a risk factor for hyperuricemia with an odd ratio of 4.536 for men and 2.730 for women.

CONCLUSIONS

For hyperuricemia, hyperthyroidism was an important risk factor that should not be neglected, especially for men.

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.

Hypothyroidism in hospitalized elderly patients: a sign of worse prognosis

PURPOSE

Overt hypothyroidism has adverse clinical consequences and might worsen prognosis in critically ill elderly patients. However, the difficult interpretation of thyroid function tests (TFT) due to non-thyroidal illness (NTI) has led to discouragement of screening for thyroid dysfunction. Our aim was to determine the prevalence of TFT compatible with hypothyroidism and to study its influence on mortality among hospitalized elderly patients.

METHODS

In this prospective study we consecutively included all patients ≥60 years admitted by the Internal Medicine Department to the hospital ward (n = 451) of the Cesar Milstein Hospital in Buenos Aires, Argentina. TFT were done on day 1 and 8. Thyroid function categories were defined as overt and subclinical hypothyroidism, overt and subclinical hyperthyroidism, euthyroidism and NTI. Stage of chronic kidney disease (CKD), Adult Comorbidity Evaluation (ACE)-27, and intra-hospital mortality were recorded. The association between mortality and TFT categories was studied by Cox regression.

RESULTS

Out of 451 patients (77.0 ± 7.9 years, 54% females) 76% were categorized as NTI, 4% as overt hypothyroid, 10% as subclinical hypothyroid, 1% as subclinical hyperthyroid and 9% as euthyroid. Overt hypothyroid patients showed significantly higher mortality than the rest of the groups (25%, p < 0.05) while ACE-27 was similar among all of them (p = 0.658). In addition, patients within the overt hypothyroid category showed a higher mortality rate than NTI in a model adjusted by Stage 5-CKD, ACE-27, sex and age [HR 3.1 (1.14-8.41), p < 0.026].

CONCLUSION

Overt hypothyroidism during hospitalization was associated with elevated mortality. Further studies would reveal if TFT alterations compatible with hypothyroidism should be diagnosed/treated in hospitalized elderly patients.

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

BACKGROUND

Reduced kidney function is a common public health problem that increases risk for a wide variety of adverse outcomes, making the identification of potentially modifiable factors associated with the development of incident chronic kidney disease (CKD) important. Alterations in the hypothalamic-pituitary-thyroid axis have been linked to reduced kidney function, but the association of thyroid function with the development of incident CKD is largely uncharacterized.

METHODS

Concentrations of thyroid stimulating hormone (TSH), free thyroxine (FT4), triiodothyronine (T3) and thyroid peroxidase antibody (TPOAb) were quantified in 12 785 black and white participants of the ongoing community-based prospective Atherosclerosis Risk in Communities study. Thyroid markers and clinical categories of thyroid dysfunction (euthyroidism, combined subclinical and overt hypothyroidism, combined subclinical and overt hyperthyroidism) were also evaluated for their association with reduced kidney function (estimated glomerular filtration rate <60 mL/min/1.73 m2) at study baseline and with incident CKD over a median follow-up time of 19.6 years.

RESULTS

Higher TSH and FT4 as well as lower T3 concentrations were strongly and independently associated with reduced kidney function at study baseline. The clinical entities hypothyroidism and hyperthyroidism were also associated with higher odds of baseline reduced kidney function, but this was not significant. However, none of the markers of thyroid function nor different clinical categories of thyroid dysfunction (hypothyroidism, hyperthyroidism or TPOAb positivity) were associated with incident CKD in adjusted analyses.

CONCLUSIONS

Elevated TSH, FT4 and reduced T3 concentrations were associated with reduced kidney function cross-sectionally. The lack of association with the development of incident CKD suggests that altered thyroid function in the general population is not causally related to CKD development, but screening for thyroidal status may be especially relevant in persons with reduced kidney function.

Thyroid hormones associate with risk of incident chronic kidney disease and rapid decline in renal function: a prospective investigation

Background

Thyroid hormones have been associated with renal dysfunction in cross-sectional studies. However, prospective studies exploring the effect of thyroid hormones on renal function decline were sparse and got contradictive results. We aimed to prospectively explore the associations of thyroid hormones with incident chronic kidney disease (CKD) and rapid decline in estimated glomerular filtration rate (eGFR) in Chinese adults.

Methods

The participants were from a community-based cohort including 2103 individuals aged 40 years or above without CKD at baseline. Thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxin (FT4) were measured by radioimmunoassay at baseline. Serum creatinine, urinary creatinine and albumin were measured at baseline and follow-up. CKD was defined as eGFR <60 ml/min/1.73 m² or urinary albumin-to-creatinine ratio ≥30 mg/g. Rapid eGFR decline was defined as an annual eGFR decline >3 ml/min/1.73 m².

Results

During 4 years of follow-up, 198 participants developed CKD and 165 experienced rapid eGFR decline. Compared to tertile 1, tertile 3 of FT4 levels were associated with 1.88-folds (95% confidence interval [CI], 1.27–2.77) increased risk of incident CKD; and 1.64-folds (95% CI, 1.07–2.50) increased risk of rapid eGFR decline (both P for trend ≤0.02), after adjustment for confounders. Each 1-pmol/l of FT4 was associated with 12% increased risk of incident CKD and 10% of rapid eGFR decline. Among the incident CKD individuals, FT4 was significantly associated with higher risk of concurrent complications and further outcomes of CKD. We did not find associations of FT3 or TSH with CKD or rapid eGFR decline.

Conclusions

Higher FT4, but not TSH and FT3, was associated with increased risk of incident CKD and rapid eGFR decline in middle-aged and elderly Chinese.

The association of thyroid function and the risk of kidney function decline: a population-based cohort study

OBJECTIVES

Thyroid dysfunction has been associated with kidney function decline, but mainly in cross-sectional studies. Therefore, we aimed to determine the association between thyroid and kidney function in a prospective population-based cohort study longitudinally.

DESIGN

Prospective cohort study.

METHODS

Participants aged ≥45 years from the Rotterdam Study with thyroid and kidney function assessment were included. Kidney function and new onset chronic kidney disease (CKD) were defined using estimated glomerular filtration ate (eGFR), with CKD defined as eGFR <60 mL/min/1.73 m² according to the CKD-EPI formula.

RESULTS

We included 5103 participants (mean age of 63.6 years) with a mean follow-up of 8.1 years. Cross-sectionally, higher TSH levels were associated with lower eGFR (Beta (β): -1.75 mL/min; 95% confidence interval (CI): -2.17, -1.33), in multivariable models adjusting for several cardiovascular risk factors including smoking, hypertension and history of coronary heart disease among others. In contrast, longitudinally, higher TSH levels were associated with less annual eGFR decline (β: -0.06 mL/min; CI: -0.11, -0.01) and lower CKD incidence (odds ratio 0.85, CI; 0.75, 0.96). Compared with euthyroid participants, subclinical hyperthyroid individuals had an increased risk for CKD whereas hypothyroid individuals had a decreased risk (P for trend = 0.04).

CONCLUSIONS

Hyperactive thyroid function is associated with increased risk of kidney function decline while hypothyroidism is associated with a decreased CKD risk. More insight is needed in the pathophysiological pathways connecting high thyroid function and kidney function decline.

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.

Low free triiodothyronine levels are related to symptomatic intracranial hemorrhage and poor functional outcomes after intravenous thrombolysis in acute ischemic stroke patients

BACKGROUND AND OBJECTIVE

Low free triiodothyronine (fT3) levels have been associated with increased mortality and poor functional outcomes in patients with stroke. However, the research of relationship between fT3 levels and acute ischemic stroke (AIS) patients with intravenous thrombolysis (IVT) is scarce. We aimed to investigate the association of fT3 levels with symptomatic intracranial hemorrhage (sICH) and functional outcomes at discharge in AIS patients with IVT.

METHODS

Patients with AIS admitted to West China hospital, Sichuan University, who had underwent IVT treatment, were consecutively and retrospectively included. Demographic and clinical information were collected and analyzed according to the levels of fT3. We used logistic regression analysis to estimate the multivariable adjusted association of fT3 levels and post-IVT sICH, and functional outcomes at discharge.

RESULTS

Among the 46 patients (26 males; mean age, 63.6 years) in the final analysis, 17 patients (37.0%) had fT3 levels lower than the reference range. After adjustment for age, gender, and statistically important variables (NIHSS on admission, urea levels and creatinine levels), low fT3 levels were significantly associated with post-IVT sICH (p = 0.01, OR = 0.27, 95% CI 0.10-0.77) and poor functional outcomes at discharge (p = 0.04 OR = 2.58, 95% CI 1.05-6.35).

CONCLUSION

We found that lower free T3 levels are independently related to post-IVT sICH and poor functional outcomes at discharge in AIS patients with IVT, which should be verified and extended in large cohorts in the future.

Methodology used in studies reporting chronic kidney disease prevalence: a systematic literature review

Background

Many publications report the prevalence of chronic kidney disease (CKD) in the general population. Comparisons across studies are hampered as CKD prevalence estimations are influenced by study population characteristics and laboratory methods.

Methods

For this systematic review, two researchers independently searched PubMed, MEDLINE and EMBASE to identify all original research articles that were published between 1 January 2003 and 1 November 2014 reporting the prevalence of CKD in the European adult general population. Data on study methodology and reporting of CKD prevalence results were independently extracted by two researchers.

Results

We identified 82 eligible publications and included 48 publications of individual studies for the data extraction. There was considerable variation in population sample selection. The majority of studies did not report the sampling frame used, and the response ranged from 10 to 87%. With regard to the assessment of kidney function, 67% used a Jaffe assay, whereas 13% used the enzymatic assay for creatinine determination. Isotope dilution mass spectrometry calibration was used in 29%. The CKD-EPI (52%) and MDRD (75%) equations were most often used to estimate glomerular filtration rate (GFR). CKD was defined as estimated GFR (eGFR) <60 mL/min/1.73 m² in 92% of studies. Urinary markers of CKD were assessed in 60% of the studies. CKD prevalence was reported by sex and age strata in 54 and 50% of the studies, respectively. In publications with a primary objective of reporting CKD prevalence, 39% reported a 95% confidence interval.

Conclusions

The findings from this systematic review showed considerable variation in methods for sampling the general population and assessment of kidney function across studies reporting CKD prevalence. These results are utilized to provide recommendations to help optimize both the design and the reporting of future CKD prevalence studies, which will enhance comparability of study results.

Hyperkalemia develops in some thyroidectomized patients undergoing thyroid hormone withdrawal in preparation for radioactive iodine ablation for thyroid carcinoma

OBJECTIVE

Hyponatremia is observed in hypothyroidism, but it is not known if hypo- or hyperkalemia is associated with hypothyroidism. To study these questions, we determined serum potassium (K(+)) levels in thyroidectomized patients undergoing levothyroxine withdrawal before radioactive iodine (RAI) therapy for thyroid carcinoma.

METHODS

We retrospectively studied the records of 108 patients who had undergone total thyroidectomy for thyroid carcinoma followed by levothyroxine withdrawal and then ablation with RAI at Nagasaki University Hospital from 2009-2013. Blood samples were analyzed for serum K(+) concentrations when patients were euthyroid just before levothyroxine withdrawal and hypothyroid 21 days after levothyroxine withdrawal. We determined the proportion of patients who developed hyperkalemia (K(+) ≥5 mEq/L) and hypokalemia (K(+) ≤3.5 mEq/L).

RESULTS

Five (4.6%) patients developed hyperkalemia and 2 (1.9%) patients developed hypokalemia after levothyroxine withdrawal. The mean serum K(+) level after levothyroxine withdrawal was significantly higher than before levothyroxine withdrawal (4.23 ± 0.50 mEq/L vs. 4.09 ± 0.34 mEq/L; P<.001). After levothyroxine withdrawal, serum K(+) values were significantly correlated with age, serum sodium and creatinine levels, and the estimated glomerular filtration rate but not with serum free thyroxine or thyroid-stimulating hormone concentrations. The finding of an elevated serum K(+) of >0.5 mEq/L after levothyroxine withdrawal was more prevalent with age >60 years (odds ratio [OR], 4.66; P = .026) and with the use of angiotensin-II receptor blockers or angiotensin-converting enzyme inhibitors (OR, 3.53; P = .033) in a multivariate analysis.

CONCLUSION

Hyperkalemia develops in a small percentage of hypothyroid patients after thyroid hormone withdrawal, especially in patients over 60 years of age who are using antihypertensive agents that inhibit the reninangiotensin-aldosterone system.

The relationship between thyroid function and estimated glomerular filtration rate in patients with chronic kidney disease

BACKGROUND

Recent studies have shown an increasing risk of hypothyroidism with incrementally lower estimated glomerular filtration rate (eGFR) in cohorts comprised of patients with normal to mildly impaired kidney function. We sought to confirm these findings in a nationally representative cohort of Veterans Affairs patients with moderate-to-severe chronic kidney disease (CKD).

METHODS

This study examined the association between kidney function and hypothyroidism among 461 607 veterans with Stage 3 to 5 CKD who underwent repeated measurements of serum creatinine and thyrotropin (TSH) at identical time points between October 2004 and September 2006. Kidney function was defined by eGFR using the Chronic Kidney Disease Epidemiology Collaboration formula. In primary analyses, the association between eGFR and hypothyroidism (defined as serum TSH > 5 mIU/L and/or receipt of thyroid hormone supplementation) was estimated using multivariable random effects logistic regression. In secondary analyses, the association between eGFR and serum TSH level was estimated using multivariable random effects linear regression.

RESULTS

At baseline, 68.9, 25.5, 5.3 and 0.3% of patients had Stage 3A, 3B, 4 and 5 CKD, respectively. For every 10 mL/min/1.73 m(2) lower eGFR, there was an 18% higher risk of hypothyroidism: adjusted odds ratio 1.18 [95% confidence interval (CI) 1.17-1.20, P < 0.001]. In secondary analyses, we observed that a 10 mL/min/1.73 m(2) lower eGFR was associated with a 0.11 mIU/L higher serum TSH (95% CI 0.10-0.11 mIU/L higher serum TSH, P < 0.001).

CONCLUSIONS

In a nationally representative cohort of patients with moderate-to-severe CKD, there is an inverse association between eGFR and risk of hypothyroidism.