Comparative Effectiveness of Levothyroxine, Desiccated Thyroid Extract, and Levothyroxine+Liothyronine in Hypothyroidism

A review of the safety of triiodothyronine in combination with levothyroxine for the management of hypothyroidism

There remains considerable interest in the therapeutic use of combinations of levothyroxine (LT4) and triiodothyronine (liothyronine, T3) in the management of hypothyroidism, especially where hypothyroid-like symptoms persist on optimised LT4 monotherapy. This interest appears to be increasing, despite the lack of consistent identification of clinical benefit in people with hypothyroidism in randomised trials going back two decades. Guidelines support an individualised trial of addition of T3 to LT4 for symptomatic patients on optimised LT4. A new generation of clinical trials seeks to address this issue, using thyroid-specific instruments to measure patient-reported outcomes, among other innovations. Safety is the other critical element of the therapeutic profile of a drug. In this article, we review the safety of treatment LT4 + T3, with an emphasis on side-effects suggestive of thyrotoxicosis (overtreatment with thyroid hormones). Randomised trials that evaluated LT4 + T3 did not raise clear or consistent safety issues with this treatment. This was despite the use of regimens with a lower ratio of LT4:T3 (usually 4-10:1) than recommended currently by clinical experts in the field. In addition, a real-world analysis of side-effects of a commercial LT4 + T3 treatment (LT4:T3 ratio 5:1) that were reported spontaneously to a pharmacovigilance database revealed a low rate of reports, both overall and with regard to symptoms possible reminiscent of thyrotoxicosis. Safety concerns regarding the possibility of iatrogenic thyrotoxicosis appear unlikely to limit the future guideline-driven therapeutic use of LT4:T3 combinations with a ratio of these ingredients of around 15:1.

Hypothyroidism

Hypothyroidism, the deficiency of thyroid hormone, is a common condition worldwide. It affects almost all body systems and has a wide variety of clinical presentations from being asymptomatic to, in rare cases, life threatening. The classic symptoms of hypothyroidism include fatigue, lethargy, weight gain, and cold intolerance; however, these symptoms are non-specific and the diagnosis is typically made on biochemical grounds through serum thyroid function tests. The most common cause of hypothyroidism is chronic autoimmune thyroiditis (Hashimoto's thyroiditis), although other causes, including drugs (such as amiodarone, lithium, and immune checkpoint inhibitors), radioactive-iodine treatment, and thyroid surgery, are frequent. Historically, severe iodine deficiency was the most common cause. Reference ranges for thyroid function tests are based on fixed percentiles of the population distribution, but there is increasing awareness of the need for more individualised reference intervals based on key factors such as age, sex, and special circumstances such as pregnancy. Levothyroxine monotherapy is the standard treatment for hypothyroidism; it is safe and inexpensive, restores thyroid function tests to within the reference range, and improves symptoms in the majority of patients. However, 10% of patients have persistent symptoms of ill health despite normalisation of thyroid function tests biochemically and a substantial proportion of patients on levothyroxine have thyroid-stimulating hormone concentrations outside the reference range. Ongoing symptoms despite levothyroxine treatment has led to some patients using liothyronine or desiccated thyroid extract. Taken together, these factors have led to intense debate around the treatment thresholds and treatment strategies for hypothyroidism. In this Seminar, we review the epidemiology, genetic determinants, causes, and presentation of hypothyroidism; highlight key considerations and controversies in its diagnosis and management; and provide future directions for research.

Cardiac Tamponade: A Late and Rare Finding of Hypothyroidism

"Myxedema heart" is a rare syndrome that results from severe untreated hypothyroidism. It is characterized by relative bradycardia, low-voltage electrocardiogram (EKG), cardiomyopathy, and pericardial effusion. Here, we present a case of cardiac tamponade in untreated hypothyroidism. A 49-year-old male with no prior medical or psychiatric history presented to the Emergency Department for cognitive slowing, weakness, and inappropriate behavior for several weeks. Vital signs were significant for bradycardia with normal blood pressure. Examination revealed that the patient was disheveled and alert but forgetful with slow speech, along with ataxia and muscle wasting. The EKG showed low-voltage sinus bradycardia. Laboratory workup was notable for an elevated thyroid-stimulating hormone (TSH) level of more than 100 mcIU/mL, with low free T4 and T3. Anti-thyroid peroxidase (TPO) and thyroglobulin antibodies were elevated, confirming a diagnosis of Hashimoto's thyroiditis. Treatment with intravenous levothyroxine, triiodothyronine, and hydrocortisone was started. An echocardiogram revealed a large circumferential pericardial effusion with evidence of tamponade. A pericardial drain was placed, and it drained 980 mL of sanguineous fluid. Serial echocardiograms showed a stable posterior effusion with no recurrence of the anterior pericardial effusion. Gradually, the patient's mentation, hemodynamics, and electrolyte levels improved. He was discharged on oral levothyroxine. TSH values showed sequential improvement. A large pericardial effusion with tamponade is a rare, life-threatening complication of untreated hypothyroidism. Clinicians must promptly identify myxedema and replace thyroid hormone to prevent the progression of pericardial effusion to tamponade and reverse its pathophysiology, maintaining a high level of suspicion in those at risk of poor healthcare access or inadequate health literacy.

LT4/LT3 Combination Therapy vs. Monotherapy with LT4 for Persistent Symptoms of Hypothyroidism: A Systematic Review

Regardless of the cause, hypothyroidism should be treated with levothyroxine. The objectives of management are the normalization of TSH levels and the relief of symptoms. In general, the vast majority of patients who achieve normalization of TSH levels show a resolution of symptoms; however, for a small number of individuals, symptoms persist (despite adequate control of TSH). This scenario generates a dilemma in the therapeutic approach to these patients, because even when excluding other causes or concomitant diseases that can explain the persistence of symptoms, pharmacological management strategies are scarce. Consequently, the efficacy of some less conventional approaches to therapy, such as the use of LT3 monotherapy, desiccated thyroid extracts, and LT4/LT3 combinations, in addressing persistent hypothyroid symptoms have been evaluated in multiple studies. The majority of these studies did not observe a significant benefit from these "nonconventional" therapies in comparison to results with LT4 monotherapy alone. Nevertheless, some studies report that a significant proportion of patients prefer an alternative to monotherapy with LT4. The most common approach has been to prescribe a combination of LT4 and LT3, and this review describes and analyzes the current evidence of the efficacy of LT4/LT3 combination therapy vs. LT4 monotherapy in addressing persistent hypothyroidism symptoms to provide suggested guidelines for clinicians in the management of these patients.

Evaluating the effectiveness of combined T4 and T3 therapy or desiccated thyroid versus T4 monotherapy in hypothyroidism: a systematic review and meta-analysis

BACKGROUND

Persistent symptoms in hypothyroid patients despite normalized TSH levels suggest the need for alternative treatments. This study aims to evaluate the effectiveness of combined T4 and T3 therapy or desiccated thyroid (DTE) compared to T4 monotherapy, with a focus on thyroid profile, lipid profile, and quality of life metrics.

METHODS

We conducted a systematic review in Embase, Medline/PubMed, and Web of Science up to 11/23/2023. We used the following keywords: "Armour Thyroid," OR "Thyroid extract," OR "Natural desiccated thyroid," OR "Nature-Throid," "desiccated thyroid," OR "np thyroid," OR "Synthroid," OR "levothyroxine," OR "Liothyronine," "Cytomel," OR "Thyroid USP," OR "Unithroid." AND "hypothyroidism. " We only included RCTs and excluded non-RCT, case-control studies, and non-English articles.

RESULTS

From 6,394 identified records, 16 studies qualified after screening and eligibility checks. We included two studies on desiccated thyroid and 15 studies on combined therapy. In this meta-analysis, combination therapy with T4 + T3 revealed significantly lower Free T4 levels (mean difference (MD): -0.34; 95% CI: -0.47, -0.20), Total T4 levels (mean difference: -2.20; 95% CI: -3.03, -1.37), and GHQ-28 scores (MD: -2.89; 95% CI: -3.16, -2.63), compared to T4 monotherapy. Total T3 levels were significantly higher in combined therapy (MD: 29.82; 95% CI: 22.40, 37.25). The analyses demonstrated moderate to high heterogeneity. There was no significant difference in Heart Rate, SHBG, TSH, Lipid profile, TSQ-36, and BDI Score. Subjects on DTE had significantly higher serum Total T3 levels (MD: 50.90; 95% CI: 42.39, 59.42) and significantly lower serum Total T4 (MD: -3.11; 95% CI: -3.64, -2.58) and Free T4 levels (MD: -0.50; 95% CI: -0.57, -0.43) compared to T4 monotherapy. Moreover, DTE treatment showed modestly higher TSH levels (MD: 0.49; 95% CI: 0.17, 0.80). The analyses indicated low heterogeneity. There was no significant difference in Heart Rate, SHBG, Lipid profile, TSQ-36, GHQ-28, and BDI Score.

CONCLUSIONS

Our study revealed that combined therapy and DTE lead to higher T3 and lower T4 levels, compared to T4 monotherapy in hypothyroidism. However, no significant effects on heart rate, lipid profile, or quality of life were noted. Given the heterogeneity of results, personalized treatment approaches are recommended.

Potential Risks and Benefits of Desiccated Thyroid Extract for the Treatment of Hypothyroidism: A Systematic Review

Background: Desiccated thyroid extract (DTE) is no longer recommended for the treatment of hypothyroidism but is still in use. This review aimed to summarize the available literature on treatment with DTE in adult patients with hypothyroidism. Methods: The search was conducted up until January 6, 2024, in six electronic databases. Two reviewers independently screened all the search results. The retrieved studies compared DTE treatment with levothyroxine or combination therapy with liothyronine and levothyroxine. The primary outcome was quality of life (QoL), and the secondary outcomes included symptoms, treatment preference, adverse effects, thyroid hormone levels, thyroid autoantibodies, cardiovascular measures, and gene polymorphisms in deiodinase enzymes. Results: In the qualitative synthesis, we included nine nonrandomized studies of interventions (NRSIs), two randomized clinical trials (RCTs), and three case reports. The overall quality of evidence was moderate to very low for the various outcomes. The RCTs found no difference between treatments regarding QoL and symptom score assessments. In the NRSIs, symptom and QoL assessments were in favor of DTE. The included studies indicated that DTE may cause an increase in heart rate, lower body weight, and lower high-density lipoprotein compared with other treatment regimens, but results were conflicting. Conclusions: Most studies of DTE treatment are hampered by an inferior design, and data on long-term effects and side effects are lacking. Two RCTs could not demonstrate any difference in QoL or symptom scores when comparing DTE with other thyroid hormone substitutions. Future trials of DTE in patients with hypothyroidism should be based on adequate study designs, validated measures of QoL, patients with reduced QoL, and the assessment of biomarkers reflecting long-term adverse effects.

Gene polymorphisms and thyroid hormone signaling: implication for the treatment of hypothyroidism

INTRODUCTION

Mutations and single nucleotide polymorphisms (SNPs) in the genes encoding the network of proteins involved in thyroid hormone signaling (TH) may have implications for the effectiveness of the treatment of hypothyroidism with LT4. It is conceivable that loss-of-function mutations or SNPs impair the ability of LT4 to be activated to T3, reach its targets, and ultimately resolve symptoms of hypothyroidism. Some of these patients do benefit from therapy containing LT4 and LT3.

METHODS

Here, we reviewed the PubMed and examined gene mutations and SNPs in the TH cellular transporters, deiodinases, and TH receptors, along with their impact on TH signaling, and potential clinical implications.

RESULTS

In some mechanisms, such as the Thr92Ala-DIO2 SNP, there is a compelling rationale for reduced T4 to T3 activation that limits the effectiveness of LT4 to restore euthyroidism. In other mechanisms, a potential case can be made but more studies with a larger number of individuals are needed.

DISCUSSION/CONCLUSION

Understanding the clinical impact of the genetic makeup of LT4-treated patients may help in the preemptive identification of those individuals that would benefit from therapy containing LT3.

In Vitro and In Vivo Supplementation with Curcumin Promotes Hippocampal Neuronal Synapses Development in Rats by Inhibiting GSK-3β and Activating β-catenin

The human fetal thyroid gland is not capable of producing thyroid hormones independently until 20 weeks of gestation, and if maternal thyroid hormone synthesis is inadequate in early pregnancy, fetal brain and nerve development may be affected by maternal hypothyroidism. Curcumin, which is isolated from turmeric (Curcuma longa), has been shown to be effective in repairing neurological disorders and is effective in relieving nerve damage when consumed over a long period of time. In this experiment, we investigated the effect of curcumin supplementation on synaptic development of rat hippocampal neurons. A cell model of oxidative damage and a young rat model of hypothyroidism were constructed, and model cells and rats were treated with triiodothyronine (T3), tetraiodothyronine (T4), and curcumin, respectively. Damage of nerve cells and animal brain tissues was examined, and the effect of curcumin in alleviating the blocked neurodevelopment was investigated. Further modulation of GSK-3β/β-catenin was performed to investigate the mechanism of action of curcumin. Ultimately, we found that T3-, T4-, and curcumin-treated model cells and young rats had increased numbers of synapses and good neurodevelopment. At the same time, we found that curcumin inhibited the production of GSK-3β and Axin to activate β-catenin. The inhibition of β-catenin weakened the therapeutic effect of curcumin, and the differences between the indicators and the model group disappeared. Both cellular and animal experiments supported that curcumin effectively alleviated the oxidative cell damage caused by thyroxine deficiency and activated the synaptogenic ability of nerve synapses by inhibiting GSK-3β and protecting β-catenin activity.

Quality of life, daily functioning, and symptoms in hypothyroid patients on thyroid replacement therapy: A Dutch survey

Objective

To explore the nature and extent of possible residual complaints among Dutch hypothyroid patients using thyroid replacement therapy, we initiated a comprehensive study measuring health-related quality of life (QoL), daily functioning, and hypothyroidism-associated symptoms in patients and control persons.

Methods

An online survey measuring thyroid-specific QoL (ThyPRO), daily functioning, and hypothyroidism-associated symptoms (ThySHI) was distributed among treated hypothyroid patients and control individuals. The advertising text was formulated in an open-ended manner. Patients also provided their most recent thyroid blood values and their thyroid medication.

Results

There was a large-sized impairment of QoL (Cohen's d = 1.04, +93 % ThyPRO score) in hypothyroid patients on thyroid replacement therapy (n = 1195) as compared to controls (n = 236). Daily functioning was significantly reduced i.e., general health (-38 %), problems with vigorous- (+64 %) and moderate activities (+77 %). Almost 80 % of patients reported having complaints despite thyroid medication and in-range thyroid blood values, with 75 % expressing a desire for improved treatment options for hypothyroidism (total n = 1194). Hypothyroid patients experienced 2.8 times more intense hypothyroidism-associated symptoms than controls (n = 865, n = 203 resp). Patients' median reported serum concentrations were: TSH 0.90 mU/L, FT4 17.0 pmol/L, and FT3 2.67 pmol/L, with 52 % having low T3 levels (<3.1 pmol/L). The QoL was not found to be related to age, sex, BMI, menopausal status, stress, serum thyroid parameters, the origin and duration of hypothyroidism, the type of thyroid medication, or the LT4 dose used.

Conclusions

Our study revealed major reductions in quality of life and daily functioning, and nearly three times more intense hypothyroidism-associated symptoms in treated hypothyroid patients as compared to controls, despite treatment and largely in-range serum TSH/FT4 concentrations. The QoL was not associated with serum thyroid parameters. We recommend future research into the origin of persisting complaints and the development of improved treatment modalities for hypothyroidism.

A Cross-Sectional Analysis of Cardiovascular and Bone Health Care Utilization During Treatment With Thyroid Hormone

CONTEXT

Combination therapy with levothyroxine and liothyronine (LT4 + LT3) and desiccated thyroid extract (DTE) make up >10% of new thyroid hormone (TH) prescriptions in the United States.

OBJECTIVE

To assess health care utilization related to cardiovascular disease (CVD) and bone health (BH) events (atrial fibrillation [AF], heart failure [HF], myocardial infarction [MI], stroke, and osteoporosis/fractures [FX]) in participants taking LT4+LT3 or DTE surveyed in the Medical Expenditure Panel Survey database.

MATERIALS AND METHODS

Multi-year cross-sectional analysis examining 5437 participants (≥18 years old) treated with LT4, LT4+LT3, or DTE between 2016 and 2020. Health care utilization was assessed through outpatient, emergency, and hospital visits for AF, HF, MI, stroke, FX, and a composite index. A weighted analysis provided national estimates of health care utilization parameters. Utilization was re-analyzed following propensity score-based matching to balance sociodemographic and clinical covariates between treatment groups. Additionally, provider type and specialty data were obtained from visits associated with TH prescriptions.

RESULTS

5106 participants were treated with LT4 monotherapy, 252 with DTE, and 79 with LT4 + LT3. Prevalence of combined outpatient CVD and BH-related care utilization was lower among DTE/LT4+LT3 vs LT4 users (3.5% vs 7.7%; P = .008). There were no differences in emergency/hospital events. After covariate balancing, CVD and BH-related care utilization was similar between groups in outpatient and emergency/hospital settings. LT3 and DTE made up 7.6% of all TH prescriptions. For visits associated with DTE prescriptions, nurse practitioners and alternative medicine professionals were more likely to be identified as the primary provider type.

CONCLUSION

No significant differences in CVD- and BH-related health care utilization were identified between LT4 and DTE/LT4+LT3 users after covariate balancing. Non-MD providers were more likely to prescribe DTE.

Real Practice Assessment of Persistent Symptoms After Initiation of Levothyroxine

OBJECTIVE

Levothyroxine (LT4) is the standard treatment for hypothyroidism. However, certain patients experience persistent symptoms even after achieving euthyroid status with LT4 therapy. We aimed to determine the frequency of persistent or new symptoms in patients with hypothyroidism after initiating LT4.

METHODS

This retrospective study included patients with hypothyroidism who started on LT4 between January 2017 and December 2019 at Mayo Clinic in Rochester, Minnesota, USA. Five hundred patient charts were randomly selected for review. Patients with at least 1 documented follow-up encounter after LT4 initiation were evaluated for ≤3 follow-up visits regarding their biochemical status and symptoms.

RESULTS

We included 356 patients, a majority of whom were female (66.6%), white (92.3%), and obese (71.9%), with an average age of 59.5 years. At the baseline visit, approximately one-half of the patients (177/356, 47.7%) reported hypothyroid symptoms, with fatigue being the most common symptom. During the follow-up periods, we observed that 17.8% (28/157), 17.9% (19/106), and 19.3% (11/57) of patients had normal thyroid stimulating hormone (TSH) values but persistent symptoms, while 12.3% (19/156), 19.9% (16/107), and 8.9% (5/56) had normal TSH values but new symptoms. Overall, during each respective follow-up period, 26.7% (42/157), 27.3% (29/106), and 28% (16/57) of patients experienced persistent or new symptoms alongside normal TSH values, with fatigue being the most constant symptom.

CONCLUSION

Our findings indicate that approximately 1 in every 4 patients with hypothyroidism receiving LT4 therapy and achieving normal TSH levels experience persistent or new hypothyroid symptoms. The cause of these symptoms remains unclear, emphasizing the need for a better understanding of their underlying causes and the development of effective management strategies.

Deciphering the roles of triiodothyronine (T3) and thyroid-stimulating hormone (TSH) on cardiac electrical remodeling in clinical and experimental hypothyroidism

Hypothyroidism is the most frequent endocrine pathology. Although clinical or overt hypothyroidism has been traditionally associated to low T3 / T4 and high thyrotropin (TSH) circulating levels, other forms exist such as subclinical hypothyroidism, characterized by normal blood T3 / T4 and high TSH. In its different forms is estimated to affect approximately 10% of the population, especially women, in a 5:1 ratio with respect to men. Among its consequences are alterations in cardiac electrical activity, especially in the repolarization phase, which is accompanied by an increased susceptibility to cardiac arrhythmias. Although these alterations have traditionally been attributed to thyroid hormone deficiency, recent studies, both clinical trials and experimental models, demonstrate a fundamental role of TSH in cardiac electrical remodeling. Thus, both metabolic thyroid hormones and TSH regulate cardiac ion channel expression in many and varied ways. This means that the different combinations of hormones that predominate in different types of hypothyroidism (overt, subclinic, primary, central) can generate different forms of cardiac electrical remodeling. These new findings are raising the relevant question of whether serum TSH reference ranges should be redefined.

Emerging Therapies in Hypothyroidism

Levothyroxine (LT4) is effective for most patients with hypothyroidism. However, a minority of the patients remain symptomatic despite the normalization of serum thyrotropin levels. Randomized clinical trials including all types of patients with hypothyroidism revealed that combination levothyroxine and liothyronine (LT4+LT3) therapy is safe and is the preferred choice of patients versus LT4 alone. Many patients who do not fully benefit from LT4 experience improved quality of life and cognition after switching to LT4+LT3. For these patients, new slow-release LT3 formulations that provide stable serum T3 levels are being tested. In addition, progress in regenerative technology has led to the development of human thyroid organoids that restore euthyroidism after being transplanted into hypothyroid mice. Finally, there is a new understanding that, under certain conditions, T3 signaling may be compromised in a tissue-specific fashion while systemic thyroid function is preserved. This is seen, for example, in patients with metabolic (dysfunction)-associated fatty liver disease, for whom liver-selective T3-like molecules have been utilized successfully in clinical trials.

Association of DIO2 and MCT10 Polymorphisms With Persistent Symptoms in LT4-Treated Patients in the UK Biobank

CONTEXT

Some evidence suggests gene-treatment interactions might cause persistent symptoms in individuals receiving levothyroxine (LT4) treatment.

OBJECTIVE

We investigated, as previously hypothesized, if single-nucleotide variations (SNVs; formerly single-nucleotide polymorphisms) in rs225014 (Thr92Ala), rs225015, or rs12885300 (ORFa-Gly3Asp) in the deiodinase 2 gene (DIO2), or rs17606253 in the monocarboxylate transporter 10 gene (MCT10) were associated with outcomes indicative of local tissue hypothyroidism in LT4-treated patients and controls.

METHODS

We included 18 761 LT4-treated patients and 360 534 controls in a population-based cross-sectional study in the UK Biobank. LT4 treatment was defined as a diagnosis of hypothyroidism and self-reported use of LT4 without use of 3,5,3'-triiodothyronine. Outcomes were psychological well-being, cognitive function, and cardiovascular risk factors. Associations were evaluated by linear, logistic, or ordinal logistic multiple regression. Adjustments included sex, age, sex-age interaction, and genetic principal components 1 to 10.

RESULTS

Compared to controls, LT4 treatment was adversely associated with almost all outcomes, most noteworthy: Increased frequency of tiredness (P < .001), decreased well-being factor score (P < .001), increased reaction-time (P < .001), and increased body mass index (P < .001). Except for a significant association between the minor rs225015 A allele and financial dissatisfaction, there was no association of rs225014, rs225015, rs12885300, or rs17606253 with any outcomes in LT4-treated patients. For all outcomes, carrying the risk allele at these 4 SNVs did not amplify symptoms associated with LT4 treatment compared to controls.

CONCLUSION

rs225014, rs225015, rs12885300, and rs17606253 could not explain changed psychological well-being, cognitive function, or cardiovascular risk factors in LT4-treated patients. Our findings do not support a gene-treatment interaction between these SNVs and LT4 treatment.

Longevity, demographic characteristics, and socio-economic status are linked to triiodothyronine levels in the general population

The hypothalamic-pituitary-thyroid (HPT) axis is fundamental to human biology, exerting central control over energy expenditure and body temperature. However, the consequences of normal physiologic HPT-axis variation in populations without diagnosed thyroid disease are poorly understood. Using nationally representative data from the 2007 to 2012 National Health and Nutrition Examination Survey, we explore relationships with demographic characteristics, longevity, and socio-economic factors. We find much larger variation across age in free T3 than other HPT-axis hormones. T3 and T4 have opposite relationships to mortality: free T3 is inversely related and free T4 is positively related to the likelihood of death. Free T3 and household income are negatively related, particularly at lower incomes. Finally, free T3 among older adults is associated with labor both in terms of unemployment and hours worked. Physiologic TSH/T4 explain only 1.7% of T3 variation, and neither are appreciably correlated to socio-economic outcomes. Taken together, our data suggest an unappreciated complexity of the HPT-axis signaling cascade broadly such that TSH and T4 may not be accurate surrogates of free T3. Furthermore, we find that subclinical variation in the HPT-axis effector hormone T3 is an important and overlooked factor linking socio-economic forces, human biology, and aging.

Natural desiccated thyroid for the treatment of hypothyroidism?

Primary hypothyroidism affects about 3% of the general population in Europe. Early treatments in the late 19th Century involved subcutaneous as well as oral administration of thyroid extract. Until the early 1970s, the majority of people across the world with hypothyroidism were treated with natural desiccated thyroid (NDT) (derived from pig thyroid glands) in various formulations, with the majority of people since then being treated with levothyroxine (L-thyroxine). There is emerging evidence that may account for the efficacy of liothyronine (NDT contains a mixture of levothyroxine and liothyronine) in people who are symptomatically unresponsive to levothyroxine. While this is a highly selected group of people, the severity and chronicity of their symptoms and the fact that many patients have found their symptoms to be alleviated, can be viewed as valid evidence for the potential benefit of NDT when given after careful consideration of other differential diagnoses and other treatment options.

Randomized double-blind placebo-controlled trial on levothyroxine and liothyronine combination therapy in totally thyroidectomized subjects: the LEVOLIO study

OBJECTIVE

Despite having normal thyroid-stimulating hormone levels, many hypothyroid patients are dissatisfied with the treatment. The primary aim of this study was to evaluate the effect of twice-daily, combination therapy with levothyroxine (LT4) and liothyronine (LT3), at doses adapted according to TSH-level, on peripheral tissues as reflected by sex hormone binding globulin (SHBG) levels in totally thyroidectomized patients. Changes in other tissue markers and quality of life considering DIO2-rs225014 and MCT10-rs17606253 genetic variants were also assessed.

DESIGN

Double-blind, randomized, placebo-controlled.

METHODS

One hundred and forty-one subjects were randomized to LT4 + LT3 group (LT4 + LT3 in the morning and LT3 in the evening; n = 70) or placebo group (LT4 in the morning and placebo in the evening; n = 71). Pituitary-thyroid axis compensation was assessed after 6, 12, and 24 weeks. Clinical parameters, quality of life, and tissue markers (sex hormone binding globulin, serum lipids, bone markers) were evaluated at 12 and 24 weeks. DIO2 and MCT10 single nucleotide polymorphisms were genotyped.

RESULTS

The LT4 + LT3 group was treated with mean daily LT3 doses of 5.00 µg, with a mean daily LT4 reduction of 15 µg. After 6 months of treatment, neither SHBG and other tissue markers nor quality of life differed significantly between groups. Combination treatment required greater dose adjustments than placebo (25% vs 54%, P < .001), due to thyroid-stimulating hormone reduction, without hyperthyroidism signs or symptoms. At the end of treatment, the LT4 + placebo group had significantly lower fT3/fT4 compared to the LT4 + LT3 group (0.26 ± 0.05 vs 0.32 ± 0.08, P < .001). No preference for combination therapy was found. Genetic variants did not influence any outcomes.

CONCLUSIONS

Six months of combination therapy with twice-daily LT3 dose adapted according to TSH-level do not significantly change peripheral tissue response or quality of life, despite an increase in the fT3/fT4 ratio.

Demographic, Healthcare Access, and Dietary Factors Associated With Thyroid Hormone Treatments for Hypothyroidism

CONTEXT

Clinical guidelines have recommended a trial of liothyronine (LT3) with levothyroxine (LT4) in select patients with hypothyroidism. However, little is known about the real-world use of LT3 and desiccated thyroid extract (DTE) and the characteristics of patients treated with LT3 and DTE.

OBJECTIVES

(1) Determine national trends of new LT4, LT3, and DTE prescriptions in the United States; (2) determine whether sociodemographic, healthcare access, and dietary factors are associated with different thyroid hormone (TH) therapies.

METHODS

Parallel cross-sectional studies were conducted using 2 datasets: (1) a national patient claims dataset (2010-2020) and (2) the National Health and Nutrition Examination Study (NHANES) dataset (1999-2016). Included participants had a diagnosis of primary or subclinical hypothyroidism. Study outcomes included the impact of demographics and healthcare access on differences in the proportion of TH therapies consisting of LT4, LT3, and DTE (patient claims) and differences in dietary behaviors between DTE-treated participants and LT4-treated matched controls (NHANES).

RESULTS

On an average annual basis, 47 711 adults received at least 1 new TH prescription, with 88.3% receiving LT4 monotherapy, 2.0% receiving LT3 therapy, and 9.4% receiving DTE therapy. The proportion receiving DTE therapy increased from 5.4% in 2010 to 10.2% in 2020. In the analysis between states, high primary care and endocrinology physician densities were associated with increased use of LT4 monotherapy (odds ratio 2.51, P < .001 and odds ratio 2.71, P < .001). DTE-treated NHANES participants (n = 73) consumed more dietary supplements compared to LT4-treated participants (n = 146) (4.7 vs 2.1, P < .001).

CONCLUSIONS

The proportion of new TH therapies containing DTE for hypothyroidism doubled since 2010 while LT3 therapies remained stable. DTE treatment was associated with decreased physician density and increased dietary supplement use.

Critical Approach to Hypothyroid Patients With Persistent Symptoms

Hypothyroidism is a common condition, and numerous studies have been published over the last decade to assess the potential risks associated with this disorder when inappropriately treated. The standard of care for treatment of hypothyroidism remains levothyroxine (LT4) at doses to achieve biochemical and clinical euthyroidism. However, about 15% of hypothyroid patients experience residual hypothyroid symptoms. Some population-based studies and international population-based surveys have confirmed dissatisfaction with LT4 treatment in some hypothyroid patients. It is well established that hypothyroid patients treated with LT4 exhibit higher serum thyroxine:triiodothyronine ratios and can have a persistent increase in cardiovascular risk factors. Moreover, variants in deiodinases and thyroid hormone transporter genes have been associated with subnormal T3 concentrations, persistent symptoms in LT4-treated patients, and improvement in response to the addition of liothyronine to LT4 therapy. The American (ATA) and European Thyroid Association (ETA) guidelines have recently evolved in their recognition of the potential limitations of LT4. This shift is reflected in prescribing patterns: Physicians' use of combination therapy is prevalent and possibly increasing. Randomized clinical trials have recently been published and, while they have found no improvement in treating hypothyroid patients, a number of important limitations did not allow generalizability. Meta-analyses have reported a preference rate for combination therapy in 46.2% hypothyroid patients treated with LT4. To promote discussions about an optimal study design, the ATA, ETA, and British Thyroid Association have recently published a consensus document. Our study provides a useful counterpoint on the controversial benefits of treating hypothyroid patients with combination therapy.

Progress Toward and Challenges Remaining for Thyroid Tissue Regeneration

Thyroid hormones play a pivotal role in diverse physiological processes, and insufficient synthesis of these hormones results in hypothyroidism, a prevalent disorder with a significant global impact. Research has shown that the residual thyroid tissue following surgery fails to fully regenerate the gland and restore normal function. The slow turnover rate of the thyroid gland and the presence of resident stem cells, which may contribute to regeneration within adult thyroid tissue, are topics of ongoing debate. This comprehensive review summarizes current research findings concerning the regeneration of the adult thyroid. Investigations have identified potential cellular mechanisms implicated in thyroid regeneration following partial tissue damage, including cells within microfollicles and a cluster of potential thyroid progenitors cells. Nevertheless, the exact mechanisms remain elusive. In cases of complete removal of the thyroid gland, regeneration does not occur, underscoring the necessity for an external source of thyroid tissue. The transplantation of thyroid organoids has emerged as a promising approach to restore thyroid function. Researchers have successfully derived thyroid organoids from various sources and demonstrated their functionality in both in vitro and in vivo animal models. Despite the challenges that still need to be addressed in achieving full maturation and functionality of human thyroid organoids, significant strides have been made in this regard. This review explores the potential of thyroid organoid transplantation and its implications for the field of regenerative medicine.

Use of liothyronine (T3) in hypothyroidism: Joint British Thyroid Association/Society for endocrinology consensus statement

Persistent symptoms in patients treated for hypothyroidism are common. Despite more than 20 years of debate, the use of liothyronine for this indication remains controversial, as numerous randomised trials have failed to show a benefit of treatment regimens that combine liothyronine (T3) with levothyroxine over levothyroxine monotherapy. This consensus statement attempts to provide practical guidance to clinicians faced with patients who have persistent symptoms during thyroid hormone replacement therapy. It applies to non-pregnant adults and is focussed on care delivered within the UK National Health Service, although it may be relevant in other healthcare environments. The statement emphasises several key clinical practice points for patients dissatisfied with treatment for hypothyroidism. Firstly, it is important to establish a diagnosis of overt hypothyroidism; patients with persistent symptoms during thyroid hormone replacement but with no clear biochemical evidence of overt hypothyroidism should first have a trial without thyroid hormone replacement. In those with established overt hypothyroidism, levothyroxine doses should be optimised aiming for a TSH in the 0.3-2.0 mU/L range for 3 to 6 months before a therapeutic response can be assessed. In some patients, it may be acceptable to have serum TSH below reference range (e.g. 0.1-0.3 mU/L), but not fully suppressed in the long term. We suggest that for some patients with confirmed overt hypothyroidism and persistent symptoms who have had adequate treatment with levothyroxine and in whom other comorbidities have been excluded, a trial of liothyronine/levothyroxine combined therapy may be warranted. The decision to start treatment with liothyronine should be a shared decision between patient and clinician. However, individual clinicians should not feel obliged to start liothyronine or to continue liothyronine medication provided by other health care practitioners or accessed without medical advice, if they judge this not to be in the patient's best interest.

Levothyroxine Monotherapy: What Works Better for the Individual With Hypothyroidism?

OBJECTIVE

I explore objective data not supporting the addition of liothyronine (medication) (LT3) to levothyroxine (medication) (LT4) in patients with hypothyroidism. Accurate identification of patients with symptomatic (almost exclusively overt) hypothyroidism is important in evaluating clinical outcomes of therapies. Recent studies have documented that nearly a third of individuals who are offered thyroid hormone are euthyroid at the time of initiation. Additionally, others are clinically diagnosed without biochemical confirmation, so a sizable proportion of those started on LT4 are not hypothyroid. The assumption that nonhypothyroid symptoms will resolve with LT4 is problematic. The true underlying cause of these symptoms remains unidentified and untreated.

METHODS

In a narrative fashion I will review the positive predictive value of and correlation of symptoms consistent with hypothyroidism and confirmed hypothyroidism likely to favorably respond to thyroid hormone replacement.

RESULTS

Following a review of the reliability of thyroid-stimulating hormone (TSH) in predicting a euthyroid state, the correlation of circulating triiodothyronine (serum measurement) (T3) levels with symptoms and predictive value of T3 to forecast the outcome of adding LT3 to LT4 will be reviewed. The utility of striving for high, middle, or low TSH set points within the expected range to predict changes in clinical quality of life and the ability of blinded patients to sense subtle differences along this spectrum will be documented. In addition, the clinical impact of single nucleotide polymorphisms in the type 2 deiodinase gene will be reviewed. Finally, the overall satisfaction of selected patients with their thyroid hormone treatments will be outlined and preferences for T3-containing treatments from blinded studies will be summarized.

CONCLUSION

Basing thyroid hormone treatment decisions on patient symptoms likely results in missed diagnoses We should encourage primary care physicians to assess a differential diagnosis, exclude other diagnoses, and not assume a thyroid etiology when TSH is normal. Modifying treatment to a particular TSH target or adjusting based on a low T3 level does not seem to enhance patient outcomes. Finally, pending further trials of "symptomatic" participants, using sustained release LT3 to mimic normal physiology, and including monocarboxylate 10 transporter and Type 2 deiodinase polymorphisms and objective outcomes, I will continue to depend on therapy with LT4 monotherapy and seek alternative explanations for my patients' nonspecific symptoms.

Are We Restoring Thyroid Hormone Signaling in Levothyroxine-Treated Patients With Residual Symptoms of Hypothyroidism?

INTRODUCTION

Levothyroxine (LT4) at doses that maintain the serum thyroid-stimulating hormone levels within the normal range constitutes the standard of care for the treatment of hypothyroidism. After a few months, this eliminates the signs and symptoms of overt hypothyroidism in the majority of patients, owing to the endogenous activation of thyroxine to triiodothyronine, the biologically active thyroid hormone. Still, a small percentage of the patients (10%-20%) exhibit residual symptoms, despite having normal serum thyroid-stimulating hormone levels. These symptoms include cognitive, mood, and metabolic deficits, with a significant impairment in psychological well-being and quality of life.

OBJECTIVE

To provide a summary of progress in the approach of patients with hypothyroidism that exhibit residual symptoms despite treatment.

METHODS

We reviewed the current literature and here we focused on the mechanisms leading to a deficiency of T3 in some LT4-treated patients, the role of residual thyroid tissue and the rationale for combination therapy with LT4 + liothyronine (LT3).

RESULTS

A score of clinical trials comparing therapy with LT4 versus LT4 + LT3 concluded that both are safe and equally effective (neither is superior); however, these trials failed to recruit a sufficiently large number of patients with residual symptoms. New clinical trials that considered LT4-treated symptomatic patients revealed that such patients benefit from and prefer therapy containing LT4 + LT3; desiccated thyroid extract has also been used with similar results. A practical approach to patients with residual symptoms and on initiation of combination therapy with LT4 + LT3 is provided.

CONCLUSION

A recent joint statement of the American, British, and European Thyroid Associations recommends that a trial with combination therapy be offered to patients with hypothyroidism that do not fully benefit from therapy with LT4.

A Brief History of Glandular Therapy: More Than Just Thyroid

In the late 1800s, treatment with thyroid extract caused dramatic improvement in patients with myxedema. Shortly thereafter, multiple other glandular extracts became available, both individually and in combinations. Their use gradually fell into disfavor, partly due to overpromotion by the manufacturers. The history of the use of thyroid, pancreatic, adrenal, thymus and liver extracts suggests that glandular extracts can be beneficial, especially when potential mechanisms of action and methods of preparation are considered.

The Physiological Functions and Polymorphisms of Type II Deiodinase

Type II deiodinase (DIO2) is thought to provide triiodothyronine (T3) to the nucleus to meet intracellular needs by deiodinating the prohormone thyroxine. DIO2 is expressed widely in many tissues and plays an important role in a variety of physiological processes, such as controlling T3 content in developing tissues (e.g., bone, muscles, and skin) and the adult brain, and regulating adaptive thermogenesis in brown adipose tissue (BAT). However, the identification and cloning of DIO2 have been challenging. In recent years, several clinical investigations have focused on the Thr92Ala polymorphism, which is closely correlated with clinical syndromes such as type 2 diabetes, obesity, hypertension, and osteoarthritis. Thr92Ala-DIO2 was also found to be related to bone and neurodegenerative diseases and tumors. However, relatively few reviews have synthesized research on individual deiodinases, especially DIO2, in the past 5 years. This review summarizes current knowledge regarding the physiological functions of DIO2 in thyroid hormone signaling and adaptive thermogenesis in BAT and the brain, as well as the associations between Thr92Ala-DIO2 and bone and neurodegenerative diseases and tumors. This discussion is expected to provide insights into the physiological functions of DIO2 and the clinical syndromes associated with Thr92Ala-DIO2.

Sub-clinical triiodothyronine levels predict health, demographic, and socioeconomic outcomes

The Hypothalamic-Pituitary-Thyroid (HPT) axis is fundamental to human biology, exerting central control over energy expenditure, metabolic rate, and body temperature. However, the consequences of "normal" physiologic HPT-axis variation in non-clinical populations are poorly understood. Using nationally-representative data from the 2007-2012 NHANES, we explore relationships with demographics, mortality, and socio-economic factors. We find much larger variation across age in free T3 than other HPT-axis hormones. T3 and T4 have opposite effects on mortality: free T3 is inversely related and free T4 is positively related with likelihood of death. Free T3 and household income are negatively related, particularly at lower incomes. Finally, free T3 among older adults is associated with labor both on the extensive margin (unemployment) and intensive margin (hours worked). Physiologic TSH/T4 explain only 1% of T3 variation, and neither are appreciably correlated to socio-economic outcomes. Taken together, our data suggest an unappreciated complexity and non-linearity of the HPT-axis signaling cascade broadly such that TSH and T4 may not be accurate surrogates of free T3. Furthermore, we find that sub-clinical variation in the HPT-axis effector hormone T3 is an important and overlooked factor linking socio-economic forces, human biology, and aging.

Socioeconomic influence on treatment with liothyronine and desiccated thyroid extract in Denmark

Introduction

High compared with low educational level increases the odds of starting levothyroxine (L-T4) with a normal thyroid-stimulating hormone - the mechanism is most likely patient request. The use of liothyronine (L-T3) and desiccated thyroid extract (DTE) is also speculated to be initiated at patients' request. Therefore, the primary aim of this study was to evaluate if educational level influences treatment with L-T3 and DTE.

Material and methods

In this register-based cross-sectional study, we included all Danish citizens ≥30 years with redeemed prescription of L-T4, L-T3, or DTE during 2017-2020. We defined educational levels as short, medium, and long (<10 years, 10-12 years, and above 12 years, respectively). The association between educational level and treatment with LT3 or DTE vs only LT4 was analyzed in logistic regression models adjusted for age and sex.

Results

We included 154,360 individuals using thyroid medication of whom 3829 were treated with L-T3 (2.48%) and 430 with DTE (0.28%). The usage was highest among women (3.15%) and the age group 40-49 (5.6%). Longer education compared with short increased the odds of being treated with DTE or L-T3 (medium education odds ratio (OR) 1.61 (95% CI 1.50-1.8) and long education OR 1.95 (95% CI 1.79-2.13)). Test for trend: OR: 1.37 (95% CI 1.31-1.42). Adjustment for other covariates did not affect the results substantially.

Conclusion

Persons with a longer compared to a shorter education are more often treated with either DTE or L-T3, and the usage of these drugs is limited to less than 3% of thyroid hormone users.

Restoration of euthyroidism with levothyroxine: implications of etiology of hypothyroidism and the degree of residual endogenous thyroid function

There are many thyroid-related factors that combine with non-thyroid-related factors in order to affect the patient response to treatment of hypothyroidism, in terms of their satisfaction with therapy. Some of the thyroid-derived factors include the etiology of the hypothyroidism and the amount of residual thyroid function that the patient retains. These two factors may be intertwined and affected by a third influence, the presence of thyroid peroxidase antibodies. The downstream consequences of the interactions between these three factors may influence both free thyroxine and free triiodothyronine levels, TSH concentrations, and various thyroid biomarkers. Evidence of the widespread importance of thyroid hormones can be inferred from the multiple genes that are regulated, with their regulation affecting multiple serum biomarkers. Thyroid biomarkers may extend from various well-known serum markers such as lipids and sex hormone-binding globulin to serum levels of thyroid hormone metabolites. Moreover, the interplay between thyroid hormones and biomarkers and their relative ratios may be different depending on the hypothyroidism etiology and degree of residual thyroid function. The ultimate significance of these relationships and their effect on determining patient-reported outcomes, quality of life, and patient satisfaction is, as yet, poorly understood. However, identification of better biomarkers of thyroid function would advance the field. These biomarkers could be studied and correlated with patient-reported outcomes in future prospective studies comparing the impact of various thyroid hormone therapies.

Combined T4 + T3 therapy versus T4 monotherapy effect on psychological health in hypothyroidism: A systematic review and meta-analysis

PURPOSE

To evaluate whether T4 + T3 combination therapy had advantages in improving psychological health compared with T4 monotherapy.

METHODS

We searched PubMed, Embase, Cochrane Library, and Web of Science from January 2000 to March 2021, and updated in September 2021. The inclusion criteria (prospective study, published in English, had a T4 + T3 combination therapy test group and a T4 monotherapy control group, patients aged ≥18 years and with overt primary hypothyroidism, and published after January 2000) were applied by two reviewers; any disagreement was resolved by a third reviewer. The two reviewers independently extracted data using a standard data form and assessed the risk of bias using the Cochrane risk of bias tool. Coprimary outcomes included the psychological health measures of depression, fatigue, pain, anxiety and anger, measured using validated and reliable instruments.

RESULTS

Eighteen of 2029 studies (883 patients) were included in the meta-analysis. No significant difference was found between T4 + T3 combination therapy and T4 monotherapy with regard to depression (standardized mean difference [SMD]: -0.06, 95% confidence interval [CI]: -0.18; 0.07), fatigue (SMD: 0.06, 95% CI: -0.13; 0.26), pain (SMD: -0.01, 95% CI: -0.24; 0.22), anxiety (SMD: 0.01, 95% CI: -0.15; 0.17) and anger (SMD: 0.05, 95% CI: -0.15; 0.24). Methodological heterogeneity had no influence on the results. The patients preferred combination therapy significantly.

CONCLUSIONS

Compared with T4 monotherapy, T4 + T3 combination therapy had no significant advantage in improving psychological health. For patients who are unsatisfied with LT4 monotherapy, the patient and the physician should make a joint decision concerning therapy.

Brain Fog in Hypothyroidism: What Is It, How Is It Measured, and What Can Be Done About It

Background: Some levothyroxine (LT4)-treated hypothyroid patients report a constellation of persistent and distressing cognitive symptoms that has been termed brain fog. This narrative review focuses on attempts to define and measure hypothyroid-associated brain fog, summarize possible etiologies and contributing factors, present treatment options, and propose avenues for future research. Methods: Published literature was reviewed to summarize available information on patient-reported symptoms associated with brain fog in hypothyroidism, as well as objective evidence of impairment based on neurocognitive testing and functional imaging studies. Given the limited information specific for hypothyroid-associated brain fog, relevant data from other medical conditions associated with brain fog were also reviewed and incorporated into recommendations for clinical care and future research areas. Results: Hypothyroid-associated brain fog has not been well defined or quantitated, and the underlying pathophysiology is unclear. Symptoms vary among patients but commonly include fatigue, depressed mood, and cognitive difficulties in the areas of memory and executive function. Symptoms often predate the diagnosis of hypothyroidism, and the magnitude of cognitive impairment can range from mild to severe. Regardless of severity, these symptoms are associated with impaired quality of life and cause dissatisfaction with treatment, so often lead to requests for alternate therapies. Disease-specific and psychological factors impact the experience of brain fog in complex ways, including potential limitations in LT4 monotherapy, self-knowledge of a disease state, and expectations for therapeutic effects. Conclusions: Brain fog is a variable symptom complex in people with hypothyroidism, causing significant distress and diminished quality of life. In the absence of proven therapies, individualized treatment plans are recommended, which incorporate thyroid-specific, general medical, and psychosocial approaches. In particular, cognitive rehabilitation is an underutilized technique that is beneficial in other medical conditions associated with brain fog and could improve symptoms in hypothyroid people. The limitations in our current knowledge and questions presented throughout this review highlight a major need for clinical research in this understudied area. Future research should include attention to standardization of survey instruments to quantitate brain fog in hypothyroid people, as well as rigorously designed intervention studies.

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.

Role of Levothyroxine/Liothyronine Combinations in Treating Hypothyroidism

Diverse causes potentially underlie decreased quality of life in biochemically euthyroid patients treated for hypothyroidism with levothyroxine. Once these contributing factors are addressed, if symptoms persist, there may be benefit to personalized use of combination therapy adding liothyronine. This approach should be carefully monitored: avoiding overtreatment and ensuring that therapy is only continued if it improves patient-reported quality of life. Most randomized clinical trials have not shown benefits, perhaps because of not targeting the most symptomatic patients. Sustained-release liothyronine preparations may soon be available for optimally designed studies assessing whether combination therapy provides superior therapy for hypothyroidism in select patients.

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

BACKGROUND

Inconsistencies in the management of hypothyroidism have been reported among endocrinologists in different European countries. Aim of this study was to explore Czech endocrinologists' use of thyroid hormones in hypothyroid and euthyroid patients.

METHODS

We used a web-based survey containing 32 questions regarding the use of thyroid hormones. Four-hundred thirty-two members of the Czech Society of Endocrinology received an e-mail invitation to participate in the survey.

RESULTS

We received and analysed 157 responses (112 females and 45 males) from the 432 members (36.3%). According to 99.4% of the respondents, levothyroxine (LT4) is the primary drug of choice for the treatment of hypothyroidism. Liothyronine (LT3) was used in clinical practice by 29.9% of responders. According to 90.5% of respondents, thyroid hormones may be indicated in biochemically euthyroid patients. Female physicians prescribe thyroid hormones in euthyroid infertile women with high antibody levels more frequently than male physicians (P = 0.003). Most Czech endocrinologists (76.4%) consider combined therapy with LT4 and LT3 in various clinical scenarios, but only 1 of 29 hypothyroid physicians (3.5%) would recommend it to their patients, and only 4 out of 128 respondents (3.1%) would consider LT3 or desiccated thyroid for themselves, if diagnosed with hypothyroidism.

CONCLUSION

LT4 is the primary thyroid hormone used in the Czech Republic for treatment of hypothyroidism. At variance with thyroid guideline recommendations, Czech endocrinologists are quite liberal when prescribing thyroid hormones to euthyroid patients and in the use of LT4/LT3 combination treatment for hypothyroid patients with persisting symptoms.

The relevance of T3 in the management of hypothyroidism

Levothyroxine monotherapy has been the standard of care for treatment of hypothyroidism for more than 40 years. However, patients treated with levothyroxine have relatively lower serum tri-iodothyronine (T₃) concentrations than the general population, and symptoms of hypothyroidism persist for some patients despite normalisation of thyroid-stimulating hormone (TSH) concentrations. The understanding that maintenance of normal T₃ concentrations is the priority for the thyroid axis has redirected the clinical focus to serum T₃ concentrations in patients with hypothyroidism. This Personal View explores whether it is currently feasible to identify patients who could be considered for liothyronine supplementation in combination with levothyroxine. Genetic profiling stands out as a potential future tool to identify patients who do not respond well to levothyroxine due to suboptimal peripheral thyroxine (T₄) activation. Moreover, new slow-release liothyronine preparations are being developed to be trialled in these symptomatic patients, in an attempt to restore T₃ concentrations and provide conclusive results for the use of T₄ plus T₃ combination therapy.

Primary hypothyroidism and quality of life

In the 1970s, treatment with thyroid extract was superseded by levothyroxine, a synthetic L form of tetraiodothyronine. Since then, no major innovation has emerged for the treatment of hypothyroidism. The biochemical definition of subclinical hypothyroidism is a matter of debate. Indiscriminate screening for hypothyroidism has led to overdiagnosis and treatment initiation at lower serum levels of thyroid-stimulating hormone (TSH) than previously. Adverse health effects have been documented in individuals with hypothyroidism or hyperthyroidism, and these adverse effects can affect health-related quality of life (QOL). Levothyroxine substitution improves, but does not always normalize, QOL, especially for individuals with mild hypothyroidism. However, neither studies combining levothyroxine and liothyronine (the synthetic form of tri-iodothyronine) nor the use of desiccated thyroid extract have shown robust improvements in patient satisfaction. Future studies should focus not only on a better understanding of an individual's TSH set point (the innate narrow physiological range of serum concentration of TSH in an individual, before the onset of hypothyroidism) and alternative thyroid hormone combinations and formulations, but also on autoimmunity and comorbidities unrelated to hypothyroidism as drivers of patient dissatisfaction. Attention to the long-term health consequences of hypothyroidism, beyond QOL, and the risks of overtreatment is imperative.

Optimal Thyroid Hormone Replacement

Hypothyroidism is a common endocrinopathy, and levothyroxine is frequently prescribed. Despite the basic tenets of initiating and adjusting levothyroxine being agreed on, there are many nuances and complexities to consistently maintaining euthyroidism. Understanding the impact of patient weight and residual thyroid function on initial levothyroxine dosage and consideration of age, comorbidities, thyrotropin goal, life stage, and quality of life as levothyroxine is adjusted can be challenging and continually evolving. Because levothyroxine is a lifelong medication, it is important to avoid risks from periods of overtreatment or undertreatment. For the subset of patients not restored to baseline health with levothyroxine, causes arising from all aspects of the patient's life (coexistent medical conditions, stressors, lifestyle, psychosocial factors) should be broadly considered. If such factors do not appear to be contributing, and biochemical euthyroidism has been successfully maintained, there may be benefit to a trial of combination therapy with levothyroxine and liothyronine. This is not supported by the majority of randomized clinical trials, but may be supported by other studies providing lower-quality evidence and by animal studies. Given this discrepancy, it is important that any trial of combination therapy be continued only as long as a patient benefit is being enjoyed. Monitoring for adverse effects, particularly in older or frail individuals, is necessary and combination therapy should not be used during pregnancy. A sustained-release liothyronine preparation has completed phase 1 testing and may soon be available for better designed and powered studies assessing whether combination therapy provides superior therapy for hypothyroidism.

Case Report: Myxedema Coma Caused by Immunoglobulin A Vasculitis in a Patient With Severe Hypothyroidism

Myxedema coma is a critical disorder with high mortality rates. Disruption of the compensatory mechanism for severe and long-term hypothyroidism by various causes leads to critical conditions, including hypothermia, respiratory failure, circulatory failure, and central nervous system dysfunction. Infectious diseases, stroke, myocardial infarction, sedative drugs, and cold exposure are considered the main triggers for myxedema coma. A 59-year-old Japanese woman presented with bilateral painful purpura on her lower legs. She was diagnosed with coexisting immunoglobulin A (IgA) vasculitis and severe IgA vasculitis with nephritis and was consequently treated with intravenous methylprednisolone (125 mg/day). However, she rapidly developed multiple organ failure due to the exacerbation of severe hypothyroidism, i.e., myxedema. Her condition improved significantly following oral administration of prednisolone along with thyroxine. There was a delayed increase in the serum free triiodothyronine level, while the serum free thyroxine level was quickly restored to normal. Rapid deterioration of the patient’s condition after admission led us to diagnose her as having myxedema coma triggered by IgA vasculitis. Hence, clinicians should be aware of the risks of dynamic exacerbations in patients with hypothyroidism. Furthermore, our study suggested that combination therapy with thyroxine and liothyronine might prove effective for patients with myxedema coma, especially for those who require high-dose glucocorticoid administration.

Implementation of thyroid-related patient-reported outcomes in routine clinical practice

Patient-reported outcomes (PROs) are increasingly used in clinical practice to improve clinical care. Multiple studies show that systematic use of PROs can enhance communication with patients and improve patient satisfaction, symptom management and quality of life. Further, such data can be aggregated to examine health levels for patient groups, improve quality of care, and compare patient outcomes at the institutional, regional or national level. However, there are barriers and challenges that should be handled appropriately to achieve successful implementation of PROs in routine clinical practice. This paper briefly overviews thyroid-related PROs, describes unsolved quality of life issues in benign thyroid diseases, provides examples of routine collection of PROs, and summarizes key points facilitating successful implementation of thyroid-related PROs in routine clinical practice. Finally, the paper touches upon future directions of PRO research.

Year in Thyroidology-Recent Developments and Future Challenges: Clinical Science Review

Background: The 2021 Year in Thyroidology-Recent Developments and Future Challenges: Clinical Science Review featured key clinical research within five categories: Thyroid Nodules and Cancer, Thyroid Function and Thyroid Eye Disease, Thyroid and Pregnancy, Thyroid and Pediatrics, and Disparities in Thyroid. Methods: A literature search of PubMed from November 2019 to August 2021 was performed to identify relevant peer-reviewed articles published in English and with a focus on human subjects. Results: There were three nominees for each of the five categories and one featured article per category. The featured articles had the most potential to change clinical practice, focused on a novel topic, and/or included of strong methodology. Conclusions: There were many strong publications on thyroid between November 2019 and August 2021; the 15 nominees and 5 featured articles span a breadth of topics and methodological approaches. The featured articles all have potential to change practice patterns or to stimulate further research that will ultimately change practice patterns.

Use of Thyroid Hormones in Hypothyroid and Euthyroid Patients: A 2020 THESIS Questionnaire Survey of Members of the Swedish Endocrine Society

BACKGROUND

The standard treatment of hypothyroidism is levothyroxine (LT-4). However, there are several controversies regarding treatment of hypothyroid patients.

AIM

To investigate the Swedish endocrinologists' use of thyroid hormones in hypothyroid and euthyroid individuals.

METHODS

Physician members of the Swedish Endocrine Society (SEF) were invited by e-mail to participate in an online survey investigating this topic.

RESULTS

Out of the eligible 411 members, 116 (28.2%) responded. The majority (98.9%) stated that L-T4 is the treatment of choice. However, around 50% also prescribed liothyronine (L-T3) or a combination of L-T4+L-T3 in their practice. Combination therapy was mostly (78.5%) used in patients with persistent hypothyroid symptoms despite biochemical euthyroidism on L-T4 treatment. Most respondents prescribed L-T4 tablets and did not expect any major changes with alternative formulations such as soft-gel capsules or liquid formulations in situations influencing the bioavailability of L-T4. In euthyroid patients, 49.5% replied that treatment with thyroid hormones was never indicated, while 47.3% would consider L-T4 for euthyroid infertile women with high thyroid peroxidase (TPO) antibody levels.

CONCLUSION

The treatment of choice for hypothyroidism in Sweden is L-T4 tablets. Combination therapy with L-T4+L-T3 tablets was considered for patients with persistent symptoms despite biochemical euthyroidism. Soft-gel capsules and liquid solutions of L-T4 were infrequently prescribed. Swedish endocrinologists' deviation from endocrine society guidelines merits further study.