Impact of Hypothyroidism and Heart Failure on Hospitalization Risk

The Association Between Elevated Thyroid-Stimulating Hormone Levels and Prolonged Length of Stay Among Adult Diabetic Patients Hospitalized in Internal Medicine Departments: A Large Historical Cohort Study

Background/Objectives: Type 2 diabetes mellitus (DM2) and hypothyroidism are two of the most common endocrine disorders in clinical practice. Hospital length of stay (LOS) is a quality metric of the health systems. We evaluated the association between elevated thyroid-stimulating hormone (TSH) levels and prolonged LOS among all adult patients (age ≥ 18 years) with DM admitted to our Internal Medicine departments between 2014 and 2022. Methods: Data on patient characteristics, LOS, and in-hospital mortality were collected. A TSH level > 4.7 μIU/mL was considered as being elevated. A LOS > 75th percentile and in-hospital mortality were defined as being prolonged. Univariate and multivariable analyses were applied, and propensity score matching controlled for differences between patients with normal and those with elevated TSH levels. Results: Of the 19,066 study participants (median age 75.6 years, IQR 75.9-83.3), 1524 (7.9%) had elevated TSH levels, and prolonged LOS was significantly more common among them (before matching: 38.6% vs. 29.1%, p < 0.001; after matching: 38.7% vs. 32.6%, p = 0.001). After adjustment for potential confounders, elevated TSH levels were also associated with prolonged LOS (OR = 1.22, 95% CI 1.07-1.39, p = 0.002). Conclusions: Elevated TSH levels in diabetic patients hospitalized in Internal Medicine departments are associated with prolonged LOS, emphasizing the importance of identifying hypothyroidism among them.

Hypothyroidism and Cardiovascular Disease: A Review

Hypothyroidism is an endocrine disorder more commonly in older adults. Simultaneously, this population has an increased incidence of cardiovascular risk factors and disease, which remains the leading cause of death worldwide. Thyroid hormones (THs) promote adequate function of the cardiovascular system as they exert their effects through receptors located in the myocardium and the vasculature. In hypothyroidism, this homeostasis is disrupted, which leads to the emergence of pathogenic pathways that accelerate the progression of cardiovascular disease and aggravate its outcomes in these individuals. This article has reviewed existing literature on the relationship between hypothyroidism and cardiovascular disease (CVD). We have explored the pathogenic mechanisms linking both conditions and highlighted the prevalence of cardiovascular risk factors as well as the increased incidence of cardiovascular events in overt and subclinical diseases. Furthermore, indications of hormone replacement therapy in subclinical disease and its efficacy in reducing CVD morbidities in a particular subset of patients have been discussed.

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.

Development and Validation of a Prediction Model for Incident Hypothyroidism in a National Chronic Kidney Disease Cohort

CONTEXT

Hypothyroidism is a common yet under-recognized condition in patients with chronic kidney disease (CKD), which may lead to end-organ complications if left untreated.

OBJECTIVE

We developed a prediction tool to identify CKD patients at risk for incident hypothyroidism.

METHODS

Among 15 642 patients with stages 4 to 5 CKD without evidence of pre-existing thyroid disease, we developed and validated a risk prediction tool for the development of incident hypothyroidism (defined as thyrotropin [TSH] > 5.0 mIU/L) using the Optum Labs Data Warehouse, which contains de-identified administrative claims, including medical and pharmacy claims and enrollment records for commercial and Medicare Advantage enrollees as well as electronic health record data. Patients were divided into a two-thirds development set and a one-third validation set. Prediction models were developed using Cox models to estimate probability of incident hypothyroidism.

RESULTS

There were 1650 (11%) cases of incident hypothyroidism during a median follow-up of 3.4 years. Characteristics associated with hypothyroidism included older age, White race, higher body mass index, low serum albumin, higher baseline TSH, hypertension, congestive heart failure, exposure to iodinated contrast via angiogram or computed tomography scan, and amiodarone use. Model discrimination was good with similar C-statistics in the development and validation datasets: 0.77 (95% CI 0.75-0.78) and 0.76 (95% CI 0.74-0.78), respectively. Model goodness-of-fit tests showed adequate fit in the overall cohort (P = .47) as well as in a subcohort of patients with stage 5 CKD (P = .33).

CONCLUSION

In a national cohort of CKD patients, we developed a clinical prediction tool identifying those at risk for incident hypothyroidism to inform prioritized screening, monitoring, and treatment in this population.

Purinergic signaling in thyroid disease

It is known that thyroid hormones play pivotal roles in a wide variety of pathological and physiological events. Thyroid diseases, mainly including hyperthyroidism, hypothyroidism, and thyroid cancer, are highly prevalent worldwide health problems and frequently associated with severe clinical manifestations. However, etiology of hyperthyroidism, hypothyroidism, and thyroid cancer is not fully understood. Purinergic signaling accounts for a complex network of receptors and extracellular enzymes responsible for the recognition and degradation of extracellular nucleotides and adenosine. It has been established that purinergic signaling modulates pathways in a wide range of physiopathological conditions including hypertension, diabetes, hepatic diseases, psychiatric and neurodegeneration, rheumatic immune diseases, and cancer. More recently, the purinergic system is found to exist in thyroid gland and play an important role in the pathophysiology of thyroid diseases. Therefore, throughout this review, we focus on elaborating the changes in purinergic receptors, extracellular enzymes, and extracellular nucleotides and adenosine in hyperthyroidism, hypothyroidism, and thyroid cancer. Profound understanding of the relationship between the purinergic signaling with thyroid diseases provides a promising research area for insights into the molecular basis of thyroid diseases and also develops new and exciting insights into the treatment of thyroid diseases, especially thyroid cancer.

Association between High Normal TSH Levels and Obesity in Women with Anti-Thyroid Autoantibodies (ATAs)

A positive correlation between Thyroid-Stimulating Hormone (TSH) and Body Mass Index (BMI) has been reported in many studies, but data on this topic remain controversial, especially when TSH values are in the normal range. Moreover, few studies have evaluated the co-existence of thyroid autoimmunity. This study investigated the role of thyroid autoimmunity in the interconnection between TSH, BMI, and waist circumference (WC) in euthyroid patients with overweight or obesity. We enrolled 902 patients (213 males; mean age ± SD: 45 ± 14 years; mean BMI ± SD: 35.8 ± 6.5 kg/m²), with normal serum TSH concentration; anti-thyroid autoantibodies (ATAs) were evaluated in 752 patients (186 males). Patients were divided into four BMI classes, based on WHO criteria, and the relationship between BMI, WC, and TSH was evaluated in the whole sample and compared to ATAs positivity, observed in 235 patients (44 males). No significant difference was found between TSH levels in the BMI classes. A statistically significant correlation between TSH and BMI was found only in ATAs-positive females (N = 191, Spearman rho: 0.149; p-value: 0.040). However, this finding was not confirmed when considering the WC. Our study shows a positive correlation only between TSH and BMI in obese women with positive ATAs, suggesting that in these patients, the high normal levels of TSH could be attributed to a mild thyroid failure with a possible worsening obesity-related effect, and both need a careful evaluation.

Effect of Levothyroxine Supplementation on the Cardiac Morphology and Function in Patients With Subclinical Hypothyroidism: A Systematic Review and Meta-analysis

CONTEXT

The impact of abnormal thyroid hormone levels on the cardiovascular system has been explored for decades. Recent emerging evidence suggests that subclinical thyroid dysfunction, especially subclinical hypothyroidism (SCH), significantly affects cardiac indices.

OBJECTIVE

We aimed to determine whether levothyroxine (LT4), commonly used to treat hypothyroidism, affects cardiovascular indices in SCH patients.

METHODS

This is a systematic review and meta-analysis. We searched online databases for studies analyzing cardiac morphology and functional changes in SCH patients before and after LT4 supplementation. A total of 294 SCH patients participated and finished the follow-up. The standard mean difference and 95% CI were calculated in fixed or random-effects models. The clinical outcomes analyzed in this study included 18 indicators, mainly covering cardiac morphology, myocardial performance (including various indicators of systolic and diastolic function), mitral wave flow, and systemic vascular resistance.

RESULTS

A total of 11 studies met our search criteria. All studies explicitly mentioned that serum thyrotropin levels decreased to normal at follow-up. Our results suggest that the cardiac output (CO), left ventricular ejection fraction (LVEF), and the ratio of peak E velocity/peak A velocity were all significantly increased after LT4 supplementation compared with the baseline level. However, we found no clear evidence of significant morphological changes in the heart.

CONCLUSION

Judging from the obvious changes in the CO, LVEF, and E/A ratio, LT4 supplementation can effectively improve the cardiac systolic and diastolic dysfunction prevalent in SCH patients. This study provides evidence of the recommendation for LT4 supplementation in adult SCH patients.

The association between BMI, smoking, drinking and thyroid disease: a cross-sectional study in Wuhan, China

BACKGROUND

There is no clear conclusion on the relationship between thyroid disease and obesity and lifestyle factors such as smoking and drinking. In this study, we analysed the association of body mass index (BMI), smoking and drinking with subclinical hypothyroidism (SHO) and thyroid nodules (TNs) with the results of a cross-sectional survey of urban residents in central China and discussed the potential mechanism linking these predictive factors and the two diseases.

METHODS

This study included 1279 participants who were recruited from a Chinese community in 2011 and 2012. A questionnaire, laboratory examination and ultrasound diagnosis were conducted on these participants. Binary logistic regression analysis was used to analyse these factors.

RESULTS

Overweight (BMI ≥ 25 kg/m²) was closely related to SHO and TNs in univariate and multivariate logistic regression analyses. Smoking had a protective effect on SHO and TNs, while drinking had a protective effect on TNs in univariate logistic regression and multivariate logistic regression with some covariates, but there was no significant difference between smoking and drinking and the two kinds of thyroid diseases in multivariate logistic regression analysis with all the covariates. In subgroup analysis, BMI ≥ 25 kg/m2 was significantly associated with SHO in people with positive thyroid antibodies (odds ratio (OR) = 2.221, 95 % confidence interval (CI): 1.168-4.184, P = 0.015) and smokers (OR = 2.179, 95 % CI: 1.041-4.561, P = 0.039). BMI ≥ 25 kg/m2 was significantly associated with TNs in people over 60 years old (OR = 2.069, 95 % CI: 1.149-3.724, P = 0.015) and drinkers (OR = 3.065, 95 % CI: 1.413-6.648, P = 0.005). Drinking alcohol had a protective effect on TNs in smokers (OR = 0.456, 95 % CI: 0.240-0.865, P = 0.016) and people with BMI ≥ 25 kg/m² (OR = 0.467, 95 % CI: 0.236-0.925, P = 0.029). No significant association was found between smoking and the two thyroid diseases in different subgroups.

CONCLUSIONS

Obesity is a risk factor for both TNs and SHO, especially in elderly individuals and people with positive thyroid autoantibodies. Obesity and metabolic syndrome may be more associated with TNs than SHO. Smoking may have a protective effect on thyroid disease, while drinking may have a protective effect only on TNs.

Association of Subclinical Hypothyroidism and Cardiovascular Disease With Mortality

Importance

Subclinical hypothyroidism is a common clinical entity among US adults associated in some studies with an increase in the risk of cardiovascular disease (CVD) and mortality. However, the extent to which CVD mediates the association between elevated serum thyrotropin (TSH) and mortality has not yet been well established or sufficiently quantified.

Objective

To elucidate the extent to which subclinical hypothyroidism, elevated serum TSH and normal serum free thyroxine, or high-normal TSH concentrations (ie, upper normative-range TSH concentrations) are associated with mortality through CVD among US adults.

Design, Setting, and Participants

This cohort study relied on representative samples of US adults enrolled in the National Health and Nutrition Examination Survey in 2001 to 2002, 2007 to 2008, 2009 to 2010, and 2011 to 2012 and their mortality data through 2015. Data were analyzed from January to August 2019.

Main Outcomes and Measures

Cox proportional hazards regression models were used to investigate associations between the TSH concentration category (subclinical hypothyroidism or tertiles of serum TSH concentrations within the reference range; low-normal TSH, 0.34-1.19 mIU/L; middle-normal TSH, 1.20-1.95 mIU/L; and high-normal TSH, 1.96-5.60 mIU/L) and all-cause mortality. Mediation analysis was used within the counterfactual framework to estimate natural direct associations (not through CVD) and indirect associations (through CVD).

Results

Of 9020 participants, 4658 (51.6%) were men; the mean (SD) age was 49.4 (17.8) years. Throughout follow-up (median [interquartile range], 7.3 [5.4-8.3] years), serum thyroid function test results consistent with subclinical hypothyroidism and high-normal TSH concentrations were both associated with increased all-cause mortality (subclinical hypothyroidism: hazard ratio, 1.90; 95% CI, 1.14-3.19; high-normal TSH: hazard ratio, 1.36; 95% CI, 1.07-1.73) compared with the middle-normal TSH group. Cardiovascular disease mediated 14.3% and 5.9% of the associations of subclinical hypothyroidism and high-normal TSH with all-cause mortality, respectively, with the CVD mediation being most pronounced in women (7.5%-13.7% of the association) and participants aged 60 years and older (6.0%-14.8% of the association).

Conclusions and Relevance

In this study, CVD mediated the associations of subclinical hypothyroidism and high-normal TSH concentrations with all-cause mortality in the US general population. Further studies are needed to examine the clinical benefit of thyroid hormone replacement therapy targeted to a middle-normal TSH concentration or active CVD screening for people with elevated TSH concentrations.

Congestive Heart Failure and Thyroid Dysfunction: The Role of the Low T3 Syndrome and Therapeutic Aspects

BACKGROUND

Both the morbidity and mortality rates from congestive heart failure (CHF) remain elevated despite the medical and non-medical management of the disease, thus suggesting the existence of residual risk factors such as thyroid dysfunction. Particularly, the 15-30% of patients with CHF, especially those with severe ventricular dysfunction, display the so-called low T3 syndrome (LT3S), which seems to negatively affect the cardiovascular prognosis.

OBJECTIVE

Only a few clinical trials have been carried out to verify both the safety and the efficacy of thyroid replacement in the LT3S, aiming to ameliorate the prognosis of CHF, and most of the results were controversial.

METHODS

Since the aim of the present review was to briefly overview both the indication and contraindication of triiodothyronine replacement in CHF and LT3S, the authors searched PubMed using the medical subject headings (MeSH) related to the following terms: "congestive heart failure" and "low T3 syndrome" or "euthyroid sick syndrome" or "non-thyroidal sick syndrome". The research study only focused on the narrative and systematic reviews, randomized clinical trials and meta-analysis studies which were conducted before June 2019.

RESULTS

Studies conducted in both animal models and humans provided controversial information about the effectiveness and safety of the T3 replacement for improving ventricular dysfunction, particularly in the long-term.

CONCLUSION

Further clinical trials are needed to better explore the role of LT3S in patients with CHF and its consequent therapeutic strategy in this clinical setting.

Subclinical thyroid dysfunction is associated with adverse prognosis in heart failure patients with reduced ejection fraction

BACKGROUND

Subclinical thyroid dysfunction whose typical patterns include subclinical hypothyroidism and subclinical hyperthyroidism, has been indicated to be associated with an increased risk of heart failure (HF). However, the relationship between subclinical thyroid dysfunction and the clinical outcomes of HF patients is uncertain. This meta-analysis was conducted to assess the association between subclinical thyroid dysfunction and the clinical outcomes of HF patients.

METHODS

Pubmed, Embase, Web of Science and Cochrane Central Register of Clinical Trials were searched for eligible studies published up to August 1, 2018 which reported the association between subclinical thyroid dysfunction and the clinical outcomes of HF patients. The pooled hazard ratio (HR) with the corresponding 95% confidence interval (CI) was used to assess the association.

RESULTS

Fourteen studies met the eligibility criteria and a total of 21,221 patients with heart failure were included in the meta-analysis. Compared with HF patients with euthyroidism, the pooled HR of subclinical hypothyroidism for all-cause mortality was 1.45 (95% CI 1.26-1.67) in a randomized effects model with mild heterogeneity (I² = 40.1, P = 0.073). The pooled HR of subclinical hypothyroidism for cardiac death and/or hospitalization was 1.33 (1.17-1.50) in a randomized effects model with moderate heterogeneity (I² = 69.4, P < 0.001). Subclinical hyperthyroid can increase the risk of all-cause mortality without heterogeneity (HR 1.31, 95% CI 1.10-1.55, I² = 25.5%, P = 0.225) but have no influence on the risk of cardiac death and/or hospitalization (HR 1.03, 95% CI 0.87-1.23, I² = 0.0%, P = 0.958). These significant adverse associations were also retained in subgroup analysis. Sensitivity analysis demonstrated the stability of the results of our meta-analysis.

CONCLUSIONS

Both subclinical hypothyroidism and subclinical hyperthyroidism are associated with adverse prognosis in patients with HF. Subclinical thyroid dysfunction may be a useful and promising predictor for the long-term prognosis in HF patients.