Correlation between Thyroid Stimulating Hormone and Renal Function in Euthyroid Residents of Japan: Results from the Kyushu and Okinawa Population Study (KOPS)

The Relationship between Subclinical Hypothyroidism and Carotid Intima-Media Thickness as a Potential Marker of Cardiovascular Risk: A Systematic Review and a Meta-Analysis

BACKGROUND AND OBJECTIVES

Thyroid dysfunction is known to have significant consequences on the cardiovascular system. The correlation between carotid intima-media thickness (CIMT) and subclinical hypothyroidism (SCH) has been frequently evaluated in clinical studies in recent years. This study aimed to evaluate the significance of this association through a meta-analysis.

METHODS

We conducted a systematic search of PubMed, MedLine, Scopus, and Web of Science databases using the keywords 'subclinical hypothyroidism and carotid intima-media thickness', from the beginning of each database until January 2023. We established the inclusion and exclusion criteria and considered studies that met the inclusion criteria. We used Jamovi for statistical analysis of the data.

RESULTS

We identified 39 observational studies that met the inclusion criteria, with 3430 subjects: 1545 SCH and 1885 EU. Compared to euthyroid subjects (EU), subjects with subclinical hypothyroidism (SCH) had significantly increased carotid intima-media thickness (CIMT) values; the estimated average mean difference was 0.08 (95% CI 0.05 to 0.10), p < 0.01, I2 = 93.82%. After the sensitivity analysis, a total of 19 from the 39 abovementioned studies were analyzed, with most studies showing a positive association between SCH and thickening of the carotid wall; the estimated average mean difference was 0.04 (95% CI 0.02 to 0.07), p = 0.03, I2 = 77.7. In addition, female sex, advanced age, and high cholesterol levels statistically significantly influenced this association.

CONCLUSIONS

Our meta-analysis indicates a significant positive association between SCH and increased CIMT, but with some limitations.

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.

Subclinical Hypothyroidism, Kidney, and Heart from Normal to Uremic Milieu

Thyroid hormone (TH) imbalances, particularly subclinical hypothyroidism (SCHT), are associated with chronic kidney disease (CKD) and end-stage kidney disease (ESKD). SCHT is more prevalent in CKD and ESKD patients than in the general population, and this condition increases the risk of cardiovascular disease (CVD) morbidity and mortality. The risk of CVD is higher in CKD and ESKD patients compared with the general population. Traditional and nontraditional risk factors, including TH abnormalities, contribute to the high CVD burden in CKD and ESKD patients. The review discusses the link between CKD and hypothyroidism, with a focus on SCHT, and the mechanisms that lead to CVD burden.

Thyroid function, glycemic control, and diabetic nephropathy in patients with type 2 diabetes over 24 months: prospective observational study

BACKGROUND

The higher prevalence of thyroid dysfunction in type 1 diabetes patients has been well established, whereas it is a matter of debate whether that is also observed in type 2 diabetes patients. This study was conducted to reveal whether higher prevalence of thyroid dysfunction is observed in patients with type 2 diabetes.

METHODS

We examined thyroid functions and thyroid autoantibodies in 200 patients with type 2 diabetes and 225 controls, with 24 months follow up for those with type 2 diabetes.

RESULTS

Serum free triiodothyronine (fT3) levels and fT3/free thyroxine (fT4) ratio were significantly lower, while fT4 levels were significantly higher in patients with type 2 diabetes. The number of patients with thyroid dysfunction or patients positive for thyroid autoantibodies were not different between the two groups. The fT3/fT4 ratio was positively and negatively correlated with serum c-peptide and HbA1c levels, respectively, suggesting that the difference can be attributable to insulin resistance and diabetic control. In the follow-up observation, we found no significant correlation between basal thyrotropin (TSH), fT3, fT4 or fT3/fT4 ratio with the amounts of changes of HbA1c levels at 12 or 24 months after the basal measurements. There was a negative relationship between TSH levels and eGFR at baseline measurements, but TSH levels did not seem to predict future decline of eGFR levels. No relationship was observed between urine albumin/ g‧cre levels and thyroid function.

CONCLUSION

Thyroid dysfunction and thyroid autoantibodies were not different in prevalence between patients with type 2 diabetes and controls, although in patients with type 2 diabetes, the fT3/fT4 ratio was decreased. Basal thyroid function did not predict future diabetes control or renal function within 24 months of follow-up.

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 Feedback Quantile-based Index correlates strongly to renal function in euthyroid individuals

BACKGROUND

Previous studies have reported a negative relationship between thyroid-stimulating hormone (TSH) and renal function in euthyroid individuals, but others have found that higher free thyroxine (FT4) was associated with an increased risk of chronic kidney disease. This study was designed to analyze the relationship between thyroid and renal function from a new perspective of sensitivity to thyroid hormone.

METHODS

This retrospective study included 2831 euthyroid individuals who underwent a health examination at the First Hospital of China Medical University between January 2017 and December 2018. Parametric Thyroid Feedback Quantile-based Index (PTFQIFT4), TSH index (TSHI), thyrotroph T4 resistance index (TT4RI), free triiodothyronine to FT4 ratio (FT3/FT4), the secretory capacity of the thyroid gland (SPINA-GT) and the sum activity of peripheral deiodinases (SPINA-GD) were calculated. We also innovated the TT3RI and PTFQIFT3 indices based on FT3 and TSH. Renal function was assessed by estimated glomerular filtration rate (eGFR) CKD-EPI and creatinine-cystatin C-KDIGO equations.

RESULTS

After adjustment of basic characteristics and comorbidities, linear regression showed that eGFR CKD-EPI was positively associated with FT3/FT4 (β = 23.31), and inversely correlated to PTFQI FT4 (β= -2.69) (both p < .001). When comparing the fourth versus the first quartile of PTFQI FT4, the odds ratio (OR) for a reduced renal function was 1.89 (95% CI 1.28-2.80), and the OR was 0.64 (95% CI 0.43-0.95) when comparing quartiles of FT3/FT4 (both pfor trend< .05). In addition, for every 1SD increase in PTFQI FT4, the OR for a reduced renal function was 1.27 (95%CI 1.10-1.47). TSHI, TT4RI and TT3RI also showed a negative correlation to renal function. Similar results were obtained in SPINA-GD as in FT3/FT4.

CONCLUSIONS

In euthyroid individuals, decreased sensitivity to thyroid hormone is associated with reduced renal function. The composite PTFQIFT4 index correlates more strongly to renal function than TSH or T4 alone.KEY MESSAGESDecreased sensitivity to thyroid hormone is associated with reduced renal function in the euthyroid population.The recently developed composite index PTFQIFT4 seems to correlate more strongly to renal function than individual TSH or FT4 parameters.Innovative indices TT3RI and PTFQIFT3 based on the interaction between T3 and TSH may also reflect sensitivity to thyroid hormone.

Association between thyroid-stimulating hormone (TSH) and proteinuria in relation to thyroid cyst in a euthyroid general population

Background

High normal levels of thyroid-stimulating hormone (TSH) have been reported to be associated with chronic kidney disease (CKD) among euthyroid individuals. However, there has been only limited research on the association between TSH and proteinuria, a major risk factor for the progression of renal disease.

Methods

A cross-sectional study of 1595 euthyroid individuals was conducted. All participants were within the normal range for free triiodothyronine (T3), free thyroxine (T4), and TSH. Analyses were stratified by thyroid cyst status to test the hypothesis that the absence of thyroid cysts, an indicator of latent thyroid damage, is associated with declining ability to synthesis thyroid hormone.

Results

For participants with thyroid cysts, a significant inverse association between TSH and proteinuria was observed (adjusted odds ratio (95% confidence intervals) of log-transformed TSH for proteinuria 0.40 (0.18, 0.89)). In participants without thyroid cysts, a significant positive association between those two factors was observed (2.06 (1.09, 3.90)).

Conclusions

Among euthyroid individuals in the general population, being in the normal range of TSH was found to have an ambivalent association with proteinuria. Thyroid cyst status could be an effect modifier for those associations.

Recombinant Human Thyrotropin Worsens Renal Cortical Perfusion and Renal Function in Patients After Total Thyroidectomy Due to Differentiated Thyroid Cancer

Background: Although thyrotropin (TSH) receptors are found in many nonthyroid tissues, we know little about the direct action of TSH on these receptors. Patients after total thyroidectomy for differentiated thyroid cancer (DTC) provide an interesting model for studying this issue. The administration of exogenous TSH in patients with an established thyroid state on levothyroxine (LT4) treatment allows us to study the effect of elevated TSH concentrations independent of thyroid status on the function of various organs, including the kidneys. The aim of this study was to assess the effects of the administration of recombinant human TSH (rhTSH) on renal perfusion and glomerular filtration in this group of patients. Methods: The study included 24 patients after total thyroidectomy due to DTC, without concomitant diseases, receiving only LT4 who qualified for radioiodine treatment (RIT). For two consecutive days, the patients received rhTSH and subsequently the RIT. Clinical and biochemical evaluation of thyroid and renal function was carried out before and 24 hours after the second dose of rhTSH and before the RIT. On the sixth day of hospitalization, the patients' glomerular filtration rate was re-evaluated. Kidney perfusion was assessed using color Doppler ultrasound imaging before and 24 hours after the second dose of rhTSH and before the RIT. Results: The administration of rhTSH to patients after total thyroidectomy due to DTC caused significant deterioration of renal perfusion after the second dose of rhTSH before the RIT, which was followed by a significant reduction in glomerular filtration. Furthermore, rhTSH did not significantly affect the hemodynamic parameters that could worsen renal function. Conclusions: This study indicates that TSH alone, independent of thyroid hormone concentrations, can influence renal perfusion and renal function.

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.