Thyroid Hormone Therapy and Incident Stroke

TSH Trajectories During Levothyroxine Treatment in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) Cohort

CONTEXT

Thyroid-stimulating hormone (TSH) trajectory classification represents a novel approach to defining the adequacy of levothyroxine (LT4) treatment for hypothyroidism over time.

OBJECTIVE

This is a proof of principle study that uses longitudinal clinical data, including thyroid hormone levels from a large prospective study to define classes of TSH trajectories and examine changes in cardiovascular (CV) health markers over the study period.

METHODS

Growth mixture modeling (GMM), including latent class growth analysis (LCGA), was used to classify LT4-treated individuals participating in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) based on serial TSH levels. Repeated measure analyses were then utilized to assess within-class changes in blood pressure, lipid levels, hemoglobin A1c, and CV-related medication utilization.

RESULTS

From the 621 LT4-treated study participants, the best-fit GMM approach identified 4 TSH trajectory classes, as defined by their relationship to the normal TSH range: (1) high-high normal TSH, (2) normal TSH, (3) normal to low TSH, and (4) low to normal TSH. Notably, the average baseline LT4 dose was lowest in the high-high normal TSH group (77.7 µg, P < .001). There were no significant differences in CV health markers between the classes at baseline. At least 1 significant difference in CV markers occurred in all classes, highlighted by the low to normal class, in which total and high-density lipoprotein cholesterol, triglycerides, and A1c all increased significantly (P = .049, P < .001, P < .001, and P = .001, respectively). Utilization of antihypertensive, antihyperlipidemic, and antidiabetes medications increased in all classes.

CONCLUSION

GMM/LCGA represents a viable approach to define and examine LT4 treatment by TSH trajectory. More comprehensive datasets should allow for more complex trajectory modeling and analysis of clinical outcome differences between trajectory classes.

Exploring the causal factor effects of hypothyroidism on ischemic stroke: a two-sample Mendelian randomization study

Background

Observational studies have suggested a possible association between hypothyroidism and increased risk of ischemic stroke. However, a causal relationship remains unclear.

Methods

Data on single nucleotide polymorphisms (SNPs) associated with hypothyroidism and ischemic stroke were sourced from the FinnGens database and the UK Biobank of European descent. Both databases underwent separate two-sample Mendelian randomization (MR) analyses. A subsequent meta-analysis of MR results using a random-effects model was conducted to determine the causal relationship between hypothyroidism and ischemic stroke.

Results

All five analyses indicated a positive causal relationship between hypothyroidism and ischemic stroke. MR analysis of the association between hypothyroidism and ischemic stroke yielded a result of the inverse variance weighted (IVW) method at 4.7411 (1.3598-16.5308), p = 0.0146. The analysis of ischemic stroke (without excluding controls) yielded a result of the IVW method of 4.5713 (1.3570-15.3986), p = 0.0142. MR analysis with cerebral infarction yielded a result of the IVW method at 1.0110 (1.0006-1.0215), p = 0.0373. The MR analysis with cerebrovascular disease sequelae yielded an IVW method result of 2.4556 (1.0291-5.8595), p = 0.0429. Analysis for the sequelae of cerebrovascular disease (without excluding controls) yielded an IVW method result of 2.4217 (1.0217-5.7402), p = 0.0446. No evidence of heterogeneity or horizontal pleiotropy was found. The meta-analysis of the five MR results was 2.24 (1.18-4.26), p = 0.025.

Conclusion

Our two-sample Mendelian randomization study suggested a causal relationship between hypothyroidism and ischemic stroke, indicating that hypothyroidism could be a risk factor for ischemic stroke. However, further studies are required to elucidate the underlying biological mechanisms.

Subclinical thyroid dysfunction and the risk of incident atrial fibrillation: A systematic review and meta-analysis

BACKGROUND

Thyroid hormones act on the cardiovascular system directly by modulating its function and indirectly by transcriptional regulation of gene expression in the heart and the vasculature. Studies have shown associations between overt and subclinical thyroid disorders and cardiovascular outcomes. The aim of this study was to perform a systematic review and meta-analysis to assess the potential relationships between subclinical hyper- and hypothyroidism and risk of atrial fibrillation (AF), and post-operative AF.

METHODS

MEDLINE and Scopus databases were searched from inception to 18th February 2023 for randomised controlled trials, case-control studies, and cohort studies which assessed the relationship between subclinical thyroid dysfunction and incident AF events. Risk of bias and the quality of evidence were assessed using the RoBANS tool and GRADE approach, respectively. Meta-analysis was conducted in Review Manager 5.4 using the Mantel-Haenszel statistical method and a random-effects model. Data are presented as risk ratios with 95% confidence intervals. Statistical heterogeneity amongst studies was assessed by the chi-squared (χ2) test and I2 statistic. p≤0.05 were considered significant.

RESULTS

A total of 6467 records were identified, of which 10 cohort studies met the inclusion criteria. Both subclinical hyperthyroidism and subclinical hypothyroidism were associated with an increased risk of incident AF (risk ratio (RR), 1.99; 95% confidence interval (CI), 1.43-2.77; n = 5 studies; p<0.0001 and RR, 1.19; CI, 1.03-1.39; n = 7 studies; p = 0.02, respectively). Subgroup analysis for post-operative AF revealed marked heterogeneity between studies (I2 = 84%) and association with subclinical hypothyroidism was not significant (RR, 1.41; CI, 0.89-2.22; n = 3 studies; p = 0.15).

CONCLUSIONS

The current evidence suggests that both subclinical hyperthyroidism and subclinical hypothyroidism are associated with increased risk of incident AF. Further investigation is required to determine potential causal links that would guide future clinical practice.

Thyroid hormone treatment counteracts cellular phenotypical remodeling in diabetic organs

Diabetes mellitus and alterations in thyroid hormone (TH) signaling are closely linked. Though the role of TH signaling in cell differentiation and growth is well known, it remains unclear whether its alterations contribute to the pathobiology of diabetic cells. Here, we aim to investigate whether the administration of exogenous T3 can counteract the cellular remodeling that occurs in diabetic cardiomyocytes, podocytes, and pancreatic beta cells. Treating diabetic rats with T3 prevents dedifferentiation, pathological growth, and ultrastructural alterations in podocytes and cardiomyocytes. In vitro, T3 reverses glucose-induced growth in human podocytes and cardiomyocytes, restores cardiomyocyte cytoarchitecture, and reverses pathological alterations in kidney and cardiac organoids. Finally, T3 treatment counteracts glucose-induced transdifferentiation, cell growth, and loss in pancreatic beta cells through TH receptor alpha1 activation. Our studies indicate that TH signaling activation substantially counteracts diabetes-induced pathological remodeling, and provide a potential therapeutic approach for the treatment of diabetes and its complications.

GlycA as a Novel Biomarker of Systemic Inflammation in Hypothyroidism

Background: GlycA is a novel glycoprotein biomarker of systemic inflammation and cardiovascular risk. Our objective was to assess the levels of GlycA in individuals with hypothyroidism. We also explored whether levothyroxine (LT4)-treated patients had different levels of GlycA, with attention to thyrotropin (TSH) levels. Methods: We performed a cross-sectional analysis, using baseline data from the ELSA-Brasil cohort study. We included only participants with serum TSH and GlycA levels measurements, using magnetic resonance spectroscopy (n = 4745). We excluded individuals with endogenous hyperthyroidism and those using drugs impacting thyroid function. Participants not taking LT4 and whose serum TSH was 0.4-4.0 mIU/L were classified as euthyroid (EU) and those with elevated TSH as undiagnosed hypothyroidism (UH). For those on LT4 (n = 345), adequacy of treatment was defined as TSH within the reference range. Those with TSH <0.4 mIU/L were considered over-treated (OT), and those >4.0 mIU/L, under-treated (UT). Both (UT+OT) were considered inadequately treated (IT). Group comparisons were performed by Kruskal-Wallis, adjusted Chi-square, and the post hoc Dunn test. Additional subgroup analysis were performed in patients with circulating thyroperoxidase antibodies (TPO-Ab+). Respective multivariable analyses were performed to evaluate the relationship between thyroid-related variables and GlycA levels (Generalized Linear Model), as well as an abnormal GlycA (>400 μmol/L; Logistic Binary Regression). Results: The prevalence rate of UH was 9.8% (467/4745) and, among those on LT4, only 61.7% (213/345) were adequately treated (AT). GlycA levels were higher in IT in comparison to EU (429 vs. 410 μmol/L, p < 0.01) but did not differ between UH (413 μmol/L) and euthyroidism. However, the subgroup analysis of those TPO-Ab+ showed that not only those with IT, but also those with UH, had higher levels of GlycA in comparison to euthyroidism (423 and 424 vs. 402 μmol/L, p = 0.04). This association between higher levels of GlycA and IT was maintained even in multivariable analysis (odds ratio 1.53, confidence interval 1.03 to 2.31) Lower levels of GlycA were detected in AT (405 μmol/L,) compared with OT (432 μmol/L, 0.04) and UT (423 μmol/L, p = 0.02). Conclusions: Patients with IT, both OT and UT, had higher GlycA levels, which may be associated with low-grade systemic inflammation and, possibly, increased cardiovascular risk.

Thyroid Function in Causal Relation to MRI Markers of Cerebral Small Vessel Disease: A Mendelian Randomization Analysis

CONTEXT

Observational studies have provided insufficient information on the association between thyroid function and the risk of cerebral small vessel disease (CSVD); moreover, the causality of this link is still unclear.

OBJECTIVE

This study aims to investigate whether genetically predicted variation within thyroid function is causally associated with the risk of CSVD using 2-sample Mendelian randomization (MR) analysis.

METHODS

In this 2-sample MR study with genome-wide association variants, we estimated the causal effects of genetically predicted thyrotropin (thyroid-stimulating hormone, TSH; n = 54 288), free thyroxine (FT4; n = 49 269), hypothyroidism (n = 51 823), and hyperthyroidism (n = 51 823) on 3 neuroimaging markers of CSVD, including white matter hyperintensity (WMH; n = 42 310), mean diffusivity (MD; n = 17 467), and fractional anisotropy (FA, n = 17 663). The primary analysis was conducted by the inverse variance-weighted MR method, followed by sensitivity analyses using MR-PRESSO, MR-Egger, weighted median, and weighted mode methods.

RESULTS

Genetically increased TSH was associated with increased MD (β = .311, 95% CI 0.0763, 0.548, P = .01). Genetically increased FT4 was associated with increased FA (β = .540, 95% CI 0.222, 0.858, P < .001). Sensitivity analyses using different MR methods showed similar directions but lower precision. No significant associations of hypothyroidism or hyperthyroidism with WMH, MD, or FA were found (all P > .05).

CONCLUSION

This study indicated that genetically predicted increased TSH was associated with increased MD, as well as increased FT4 with increased FA, implying the causal effect of thyroid dysfunction on white matter microstructural injury. There were no significant causal relationships of hypothyroidism or hyperthyroidism with CSVD. Further investigations should verify these findings and clarify the underlying pathophysiological mechanisms.

Levothyroxine Treatment Adequacy and Formulation Changes in Patients with Hypothyroidism: A Retrospective Study of Real-World Data from the United States

Background: The prevalence of hypothyroidism (HT) has increased over time. To assess the effectiveness of treatment, we (1) studied thyrotropin (TSH) levels among patients receiving levothyroxine (LT4) and (2) determined the percentages of patients switching among LT4 formulations. Methods: Data on patients with HT receiving LT4 from the Optum™ Clinical and Claims Database were analyzed from March 2013 through February 2020. Eligible adult patients had ≥1 medical claim with an HT diagnosis and all patients were observed for ≥12 months. Patients included in Objective 1 were indexed on a randomly selected TSH result and had ≥2 results for TSH 1-15 months apart. Patients included in Objective 2 were indexed on a randomly selected LT4 pharmacy claim and had ≥2 LT4 claims ≥1 month apart and ≥1 claim during follow-up. Outcomes were the proportion of patients with low, normal, or high (<0.45, 0.45-4.5, or >4.5 mIU/L, respectively) TSH levels and the proportion of patients switching LT4 formulations, respectively. Data were stratified by age group, sex, and insurance type. All data reported were analyzed using descriptive statistics. Results: Of patients who were in the indexed TSH group, 81.1% [confidence intervals: 80.4-81.8; n/N = 9130/11,259] achieved normal TSH values. When stratified by age group, sex, and insurance type, ≥70% of patients in each of these subgroups exhibited normal mean TSH values at follow-up. For Objective 2 (N = 25,076), 24.9% (N = 6238) of the LT4-indexed group had ≥1 formulation switch in 12 months, of which 67.3% only switched once, and 41.4% (N = 10,370) had ≥1 formulation switch in up to 24 months. A significantly higher proportion of Medicare vs. commercially insured patients had switched formulations (26.2% vs. 23.1%, p < 0.001). Conclusions: Most LT4-treated patients maintain normal TSH levels, which is an improvement vs. previous reports. Continued physician engagement and patient education are advised to further reduce the number of patients who maintain off-target TSH levels. Contrary to clinical recommendations, about 25% of patients receiving LT4 switched formulations within 1 year, with >40% switching within 2 years; among patients who switched, most only switched once.

Cardiovascular and Neuronal Consequences of Thyroid Hormones Alterations in the Ischemic Stroke

Ischemic stroke is one of the leading global causes of neurological morbidity and decease. Its etiology depends on multiple events such as cardiac embolism, brain capillaries occlusion and atherosclerosis, which ultimately culminate in blood flow interruption, incurring hypoxia and nutrient deprivation. Thyroid hormones (THs) are pleiotropic modulators of several metabolic pathways, and critically influence different aspects of tissues development. The brain is a key TH target tissue and both hypo- and hyperthyroidism, during embryonic and adult life, are associated with deranged neuronal formation and cognitive functions. Accordingly, increasing pieces of evidence are drawing attention on the consistent relationship between the THs status and the acute cerebral and cardiac diseases. However, the concrete contribution of THs systemic or local alteration to the pathology outcome still needs to be fully addressed. In this review, we aim to summarize the multiple influences that THs exert on the brain and heart patho-physiology, to deepen the reasons for the harmful effects of hypo- and hyperthyroidism on these organs and to provide insights on the intricate relationship between the THs variations and the pathological alterations that take place after the ischemic injury.

Towards De-Implementation of low-value thyroid care in older adults

PURPOSE OF REVIEW

This review discusses the current literature regarding low-value thyroid care in older adults, summarizing recent findings pertaining to screening for thyroid dysfunction and management of hypothyroidism, thyroid nodules and low-risk differentiated thyroid cancer.

RECENT FINDINGS

Despite a shift to a "less is more" paradigm for clinical thyroid care in older adults in recent years, current studies demonstrate that low-value care practices are still prevalent. Ineffective and potentially harmful services, such as routine treatment of subclinical hypothyroidism which can lead to overtreatment with thyroid hormone, inappropriate use of thyroid ultrasound, blanket fine needle aspiration biopsies of thyroid nodules, and more aggressive approaches to low-risk differentiated thyroid cancers, have been shown to contribute to adverse effects, particularly in comorbid older adults.

SUMMARY

Low-value thyroid care is common in older adults and can trigger a cascade of overdiagnosis and overtreatment leading to patient harm and increased healthcare costs, highlighting the urgent need for de-implementation efforts.

Suboptimal Thyroid Hormone Replacement Is Associated With Worse Hospital Outcomes

CONTEXT

Many patients with hypothyroidism receive suboptimal treatment that may affect hospital outcomes.

OBJECTIVE

This work aimed to identify differences in hospital outcomes between patients with and without hypothyroidism.

METHODS

A retrospective cohort study, using the propensity score-based fine stratification method to balance covariates, was conducted using a large, US-based, commercial claims database from January 1, 2008 to December 31, 2015. Participants included patients aged 64 years and younger who had a thyrotropin (TSH) level collected before a hospital admission. Covariates included age, sex, US region, type of admission, year of admission, and comorbidities. Exposure included clinical hypothyroidism, which was divided into 4 subgroups based on prehospitalization TSH level: low (TSH < 0.40 mIU/L), normal (TSH 0.40-4.50 mIU/L), intermediate (TSH 4.51-10.00 mIU/L), and high (TSH > 10.00 mIU/L).

MAIN OUTCOME MEASURES INCLUDED

length of stay (LOS), in-hospital mortality, and readmission outcomes.

RESULTS

A total of 43 478 patients were included in the final study population, of whom 8873 had a diagnosis of hypothyroidism. Those with a high prehospitalization TSH level had an LOS that was 1.2 days longer (95% CI, 1.1-1.3; P = .003), a 49% higher risk of 30-day readmission (relative risk [RR] 1.49; 95% CI, 1.20-1.85; P < .001), and a 43% higher rate of 90-day readmission (RR 1.43; 95% CI, 1.21-1.67; P < .001) compared to balanced controls. Patients with normal TSH levels exhibited decreased risk of in-hospital mortality (RR 0.46; 95% CI, 0.27-0.79; P = .004) and 90-day readmission (RR 0.92; 95% CI, 0.85-0.99; P = .02).

CONCLUSION

The results suggest suboptimal treatment of hypothyroidism is associated with worse hospital outcomes, including longer LOS and higher rate of readmission.

Heart Failure and Stroke Risks in Users of Liothyronine With or Without Levothyroxine Compared with Levothyroxine Alone: A Propensity Score-Matched Analysis

Background: Combination therapy with liothyronine (LT3) and levothyroxine (LT4) is used in patients with persistent symptoms, despite being administered an adequate dose of LT4. LT3 may also be used in some thyroid cancer patients preparing for radioactive iodine therapy. However, there is a controversy regarding the safety of LT3 use, and there has been no definite evidence of long-term safety of LT3 therapy in Asian populations. The aim of this study was to examine the long-term safety of LT3 therapy using the Common Data Model (CDM). Methods: We conducted a retrospective multicenter study across four hospital databases encoded in the Observational Medical Outcomes Partnership (OMOP) CDM. LT3 users were defined as those who received an LT3 prescription for at least 90 days (with or without LT4), and their safety outcomes were compared with those in LT4-only users after 1:4 propensity score matching. Safety outcomes included the incidences of osteoporosis, cardiovascular disease, cancer, anxiety disorder, and mood disorder. Results: We identified 1434 LT3 users and 3908 LT4-only users. There was a statistically significant difference in the incidence rate of safety outcomes between LT3 users and LT4-only users. The risks of heart failure (incidence rate ratio [IRR] = 1.664, 95% confidence interval [95% CI] 1.002-2.764, p = 0.049) and stroke (IRR = 1.757, CI 1.073-2.877, p = 0.025) were higher in LT3 users than in LT4-only users. When subgroup analysis was performed according to the presence/absence of thyroid cancer history and duration of thyroid hormone replacement, the risk of heart failure was higher in LT3 users with a history of thyroid cancer and those who underwent ≥52 weeks of LT3 therapy. In addition, the risk of stroke was higher in LT3 users without thyroid cancer history and those who underwent ≥52 weeks of LT3 therapy. Conclusions: The use of LT3 was associated with increased incidence of heart failure and stroke in patients with a longer duration of LT3 use and history of thyroid cancer. Therefore, clinicians should consider the risk of heart failure and stroke in thyroid cancer patients with long-term use of LT3. These findings require confirmation in other populations.

Concurrent Use of Thyroid Hormone Therapy and Interfering Medications in Older US Veterans

CONTEXT

Thyroid hormone management in older adults is complicated by comorbidities and polypharmacy.

OBJECTIVE

Determine the prevalence of concurrent use of thyroid hormone and medications that can interfere with thyroid hormone metabolism (amiodarone, prednisone, prednisolone, carbamazepine, phenytoin, phenobarbital, tamoxifen), and patient characteristics associated with this practice.

DESIGN

Retrospective cohort study between 2004 and 2017 (median follow-up, 56 months).

SETTING

Veterans Health Administration Corporate Data Warehouse.

PARTICIPANTS

A total of 538 137 adults ≥ 65 years prescribed thyroid hormone therapy during the study period.

MAIN OUTCOME MEASURE

Concurrent use of thyroid hormone and medications interfering with thyroid hormone metabolism.

RESULTS

Overall, 168 878 (31.4%) patients were on at least 1 interfering medication while on thyroid hormone during the study period. In multivariable analyses, Black/African-American race (odds ratio [OR], 1.25; 95% CI, 1.21-1.28, compared with White), Hispanic ethnicity (OR, 1.12; 95% CI, 1.09-1.15, compared with non-Hispanic), female (OR, 1.11; 95% CI, 1.08-1.15, compared with male), and presence of comorbidities (eg, Charlson/Deyo Comorbidity Score ≥ 2; OR, 2.50; 95% CI, 2.45-2.54, compared with 0) were more likely to be associated with concurrent use of thyroid hormone and interfering medications. Older age (eg, ≥ 85 years; OR, 0.48; 95% CI, 0.47-0.48, compared with age 65-74 years) was less likely to be associated with this practice.

CONCLUSIONS AND RELEVANCE

Almost one-third of older adults on thyroid hormone were on medications known to interfere with thyroid hormone metabolism. Our findings highlight the complexity of thyroid hormone management in older adults, especially in women and minorities.

Association of Thyroid Hormone Treatment Intensity With Cardiovascular Mortality Among US Veterans

IMPORTANCE

Cardiovascular disease is the leading cause of death in the United States. Synthetic thyroid hormones are among the 3 most commonly prescribed medications, yet studies evaluating the association between the intensity of thyroid hormone treatment and cardiovascular mortality are scarce.

OBJECTIVE

To evaluate the association between thyroid hormone treatment intensity and cardiovascular mortality.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used data on 705 307 adults who received thyroid hormone treatment from the Veterans Health Administration Corporate Data Warehouse between January 1, 2004, and December 31, 2017, with a median follow-up of 4 years (IQR, 2-9 years). Two cohorts were studied: 701 929 adults aged 18 years or older who initiated thyroid hormone treatment with at least 2 thyrotropin measurements between treatment initiation and either death or the end of the study period, and, separately, 373 981 patients with at least 2 free thyroxine (FT4) measurements. Data were merged with the National Death Index for mortality ascertainment and cause of death, and analysis was conducted from March 25 to September 2, 2020.

EXPOSURES

Time-varying serum thyrotropin and FT4 levels (euthyroidism: thyrotropin level, 0.5-5.5 mIU/L; FT4 level, 0.7-1.9 ng/dL; exogenous hyperthyroidism: thyrotropin level, <0.5 mIU/L; FT4 level, >1.9 ng/dL; exogenous hypothyroidism: thyrotropin level, >5.5 mIU/L; FT4 level, <0.7 ng/dL).

MAIN OUTCOMES AND MEASURES

Cardiovascular mortality (ie, death from cardiovascular causes, including myocardial infarction, heart failure, or stroke). Survival analyses were performed using Cox proportional hazards regression models using serum thyrotropin and FT4 levels as time-varying covariates.

RESULTS

Of the 705 307 patients in the study, 625 444 (88.7%) were men, and the median age was 67 years (IQR, 57-78 years; range, 18-110 years). Overall, 75 963 patients (10.8%) died of cardiovascular causes. After adjusting for age, sex, traditional cardiovascular risk factors (eg, hypertension, smoking, and previous cardiovascular disease or arrhythmia), patients with exogenous hyperthyroidism (eg, thyrotropin levels, <0.1 mIU/L: adjusted hazard ratio [AHR], 1.39; 95% CI, 1.32-1.47; FT4 levels, >1.9 ng/dL: AHR, 1.29; 95% CI, 1.20-1.40) and patients with exogenous hypothyroidism (eg, thyrotropin levels, >20 mIU/L: AHR, 2.67; 95% CI, 2.55-2.80; FT4 levels, <0.7 ng/dL: AHR, 1.56; 95% CI, 1.50-1.63) had increased risk of cardiovascular mortality compared with individuals with euthyroidism.

CONCLUSIONS AND RELEVANCE

This study suggests that both exogenous hyperthyroidism and exogenous hypothyroidism were associated with increased risk of cardiovascular mortality. These findings emphasize the importance of maintaining euthyroidism to decrease cardiovascular risk and death among patients receiving thyroid hormone treatment.

Use of thyroid hormones in hypothyroid and euthyroid patients: a 2020 THESIS questionnaire survey of members of the Hellenic Endocrine Society

PURPOSE

To investigate current practices of specialists in the use of thyroid hormone preparations in Greece as part of an ongoing international survey, namely THESIS-Treatment of Hypothyroidism in Europe by Specialists: an International Survey.

METHODS

An electronic link leading to an anonymized questionnaire was sent to all (n = 837) members of the Hellenic Endocrine Society.

RESULTS

In total, 501 respondents participated in the survey, though only part of the questionnaire was filled in by some participants. A total of 88.2% were endocrinologists and 57.9% worked in private practice. Levothyroxine (LT4) was the first-line choice (98.6%) for the treatment of hypothyroid patients. In total, 70.2% preferred LT4 soft-gel capsules for patients reporting intolerance to various foods. Soft-gel capsules were the preferred LT4 formulation for patients on generic LT4 and with unexplained poor biochemical control of hypothyroidism (66.3%) or inability to take LT4 fasted and separate from food/drink (68.3%). It was found that 48.4% would never use combined LT4 + LT3. However, 25% would use combination therapy for a short period in patients recovering from protracted hypothyroidism or in patients with normal serum TSH but persistent symptoms. Concerning euthyroid individuals, 31.9% considered treatment with thyroid hormones in infertile females with positive thyroid antibodies and 24.4% in patients with growing goiter. Selenium or iodine supplementation was used occasionally, mostly in patients with coexisting autoimmune thyroiditis.

CONCLUSIONS

LT4 tablets are the treatment of choice for hypothyroidism in Greece. Several conditions may lead to various other practices, some of which deviate from current evidence-based guidelines and need more scrutiny.

Evaluating health outcomes in the treatment of hypothyroidism

Clinical hypothyroidism is defined by the inadequate production of thyroid hormone from the thyroid gland to maintain normal organ system functions. For nearly all patients with clinical hypothyroidism, lifelong treatment with thyroid hormone replacement is required. The primary goal of treatment is to provide the appropriate daily dose of thyroid hormone to restore normal thyroid function for each individual patient. In current clinical practice, normalization of thyrotropin (TSH) level is the primary measure of effectiveness of treatment, however the use of a single biomarker to define adequate thyroid hormone replacement is being reevaluated. The assessment of clinical health outcomes and patient-reported outcomes (PROs), often within the context of intensity of treatment as defined by thyroid function tests (i.e., undertreatment, appropriate treatment, or overtreatment), may play a role in evaluating the effectiveness of treatment. The purpose of this narrative review is to summarize the prominent health outcomes literature in patients with treated hypothyroidism. To date, overall mortality, cardiovascular morbidity and mortality, bone health and cognitive function have been evaluated as endpoints in clinical outcomes studies in patients with treated hypothyroidism. More recent investigations have sought to establish the relationships between these end results and thyroid function during the treatment course. In addition to clinical event outcomes, patient-reported quality of life (QoL) has also been considered in the assessment of adequacy of hypothyroidism treatment. From a health care quality perspective, treatment of hypothyroidism should be evaluated not just on its effectiveness for the individual patients but also to the extent to which patients of different sociodemographic groups are treated equally. Ultimately, more research is needed to explore differences in health outcomes between different sociodemographic groups with hypothyroidism. Future prospective studies of treated hypothyroidism that integrate biochemical testing, PROs, and end result clinical outcomes could provide a more complete picture into the effectiveness of treatment of hypothyroidism.