Levothyroxine Treatment and the Risk of Cardiac Arrhythmias - Focus on the Patient Submitted to Thyroid Surgery

Pseudo-Malabsorption in High Dose Levothyroxine-Resistant Hypothyroidism

A 38-year-old woman was diagnosed with hypothyroidism during pregnancy at age 35 years and started on levothyroxine (LT4). Despite increasing the dose to 400 μg/day and adding liothyronine, her thyroid function did not improve, leading to hospitalization. Upon admission, her thyroid-stimulating hormone (TSH), free triiodothyronine (T3), and free thyroxine (T4) levels were 255 μIU/mL (255 mIU/L) (reference range [RR]: 0.35---4.94 μIU/mL; 0.35---4.94 mIU/L), 3.42 pg/mL (5.27 pmol/L) (RR: 1.71-3.71 pg/mL; 2.63-5.70 pmol/L), and 0.153 ng/dL (1.97 pmol/L) (RR: 0.70-1.48 ng/dL; 9.01-19.05 pmol/L), respectively. She reported good adherence to medication and not consuming interfering food or medication. Endoscopic examination revealed no malabsorption. A 1000-μg oral LT4 loading test showed an increase in free T4 level from 0.787 (10.1 pmol/L) to 2.40 ng/dL (30.9 pmol/L), indicating pseudo-malabsorption. After presenting the loading test results, she admitted to nonadherence. A multidisciplinary team intervened, conducting individual counseling and simplifying treatment. Post-discharge, with LT4 200 μg/day, her TSH, free T3, and free T4 levels improved to 0.496 μIU/mL (0.496 mIU/L), 5.23 pg/mL (8.05 pmol/L), and 2.19 ng/dL (28.2 pmol/L), respectively. When addressing treatment-resistant hypothyroidism, it is crucial to evaluate patient history and medication schedule and to check for malabsorption. Comprehensive interventions are recommended if nonadherence is suspected.

Levothyroxine therapy in thyroidectomized patients: ongoing challenges and controversies

This mini-review provides an update on the challenges and controversies surrounding levothyroxine therapy in thyroidectomized patients, following an extensive review on dosing strategies and available formulations. Despite efforts to establish an ideal dosage adjustment method, achieving optimal thyroid hormone replacement remains complex due to interindividual variations in the hypothalamic-pituitary-thyroid axis and the pharmacokinetic and pharmacodynamic limitations of exogenous levothyroxine. Additionally, this review highlights the importance of evaluating the risk-benefit ratio of levothyroxine therapy, particularly in the setting of TSH suppression, focusing on its effects on quality of life, bone metabolism, and cardiac rhythm. Levothyroxine-induced subclinical hyperthyroidism may contribute to an increased risk of atrial fibrillation and alterations in bone mineral density, with implications that remain a subject of debate. Given the incomplete replication of endogenous thyroid hormone action by levothyroxine monotherapy, a tailored therapeutic approach is crucial. Despite ongoing research, the optimal management of thyroidectomized patients continues to be an open issue.

Prevalence of and Predictive Factors for Hypothyroidism Following Hemithyroidectomy

PURPOSE

Hemithyroidectomy is an appropriate procedure that is recommended for a number of thyroid conditions to preserve the functional contralateral thyroid lobe, but patients who underwent a hemithyroidectomy still run the risk of developing hypothyroidism. This study aimed to determine the incidence of hypothyroidism following a hemithyroidectomy as well as predictive risk factors.

METHODS

A retrospective analysis was carried out on all patients who underwent hemithyroidectomy between 2016 and 2022. Age, gender, preoperative and postoperative thyroid stimulating hormone (TSH) and free thyroxin (FT4), side, and volume of the remaining lobe, as well as the histologic diagnosis, were all examined in the patients. To identify the predictors of hypothyroidism, statistical analyses, both univariate and multivariate, were conducted.

RESULTS

Out of 224 patients, 18.25% had hypothyroidism following surgery. This complication appeared within the first year in 88% of the cases. Patients with thyroiditis (P = .036), preoperative TSH levels greater than 1.72 mIU/L (P < .001), right side hemithyroidectomy (P = .017), and residual lobe volume less than 3.57 cm (P < .001) had a significantly higher risk of developing hypothyroidism.

CONCLUSION

After hemithyroidectomy, hypothyroidism is a major complication that should be carefully evaluated preoperatively based on risk factors of hypothyroidism. Furthermore, our results confirm the need for routine serum TSH monitoring for a minimum of 1 year following hemithyroidectomy.

Lactoferrin alleviates oxidative stress and endoplasmic reticulum stress induced by autoimmune thyroiditis by modulating the mTOR pathway in the thyroid

Autoimmune thyroiditis (AITD) is a prevalent autoimmune disorder characterized by the immune system's attack on thyroid tissue, potentially leading to thyroid dysfunction, with a current lack of effective treatment modalities. Lactoferrin, a crucial functional dietary component obtainable from food sources, primarily exists in mammalian milk. We aim to investigate whether dietary supplementation with lactoferrin can protect the thyroid in Experimental Autoimmune Thyroiditis (EAT) rats. Our study reveals significantly elevated levels of oxidative stress (OS) and endoplasmic reticulum stress (ERS) in the AITD. Lactoferrin markedly reduces OS and infiltration of inflammatory cells in the thyroid tissue of EAT rats. Furthermore, lactoferrin inhibits ERS levels in the thyroid of EAT rats and alleviates cellular apoptosis. In vivo and in vitro experiments elucidate that its protective effect is primarily achieved through the inhibition of mTOR signaling pathway activation. In summary, lactoferrin, a nutrient readily obtainable from food sources, appears to be effective in mitigating thyroid damage in AITD.

Effect of a Low-Molecular-Weight Allosteric Agonist of the Thyroid-Stimulating Hormone Receptor on Basal and Thyroliberin-Stimulated Activity of Thyroid System in Diabetic Rats

The approaches to correct thyroid deficiency include replacement therapy with thyroid hormones (THs), but such therapy causes a number of side effects. A possible alternative is thyroid-stimulating hormone (TSH) receptor activators, including allosteric agonists. The aim of this work was to study the effect of ethyl-2-(4-(4-(5-amino-6-(tert-butylcarbamoyl)-2-(methylthio)thieno[2,3-d]pyrimidin-4-yl)phenyl)-1H-1,2,3-triazol-1-yl) acetate (TPY3m), a TSH receptor allosteric agonist developed by us, on basal and thyroliberin (TRH)-stimulated TH levels and the hypothalamic-pituitary-thyroid (HPT) axis in male rats with high-fat diet/low-dose streptozotocin-induced type 2 diabetes mellitus (T2DM). Single and three-day administration of TPY3m (i.p., 20 mg/kg) was studied, and the effect of TPY3m on the HPT axis was compared with that of levothyroxine. TPY3m increased TH levels when administered to both healthy and diabetic rats, normalizing thyroxine and triiodothyronine levels in T2DM and, unlike levothyroxine, without negatively affecting TSH levels or the expression of hypothalamic and pituitary genes responsible for TSH production. TPY3m pretreatment preserved the stimulatory effects of TRH on TH levels and thyroid gene expression. This indicates the absence of competition between TPY3m and endogenous TSH for TSH receptor activation and is supported by our in vitro results on TPY3m- and TSH-stimulated adenylate cyclase activity in rat thyroid membranes. Morphological analysis of thyroid glands in diabetic rats after three-day TPY3m administration shows an increase in its functional activity without destructive changes. To summarize, TPY3m, with the activity of a partial allosteric agonist of the TSH receptor, was created as a prototype of drugs to correct thyroid insufficiency in T2DM.

Correlation Between Anxiety and Serum Thyroid Hormone Levels in Patients With Papillary Thyroid Carcinoma Undergoing Microwave Ablation

Objective: This study aims to explore the correlation between anxiety and serum thyroid hormone levels in patients with papillary thyroid carcinoma (PTC) who underwent microwave ablation (MWA). Methods: A total of 107 PTC patients who underwent MWA were recruited. Three months after MWA, serum samples were collected from each participant to analyze their thyroid-related hormone levels, including free T3 (FT3), free T4 (FT4), T3, T4, and thyroid-stimulating hormone (TSH) levels. Additionally, the Self-Rating Anxiety Scale (SAS) was used to measure anxiety levels at the same time. Linear correlation analysis was used to determine the correlation between anxiety and serum thyroid hormone levels. Results: SAS scores among the 107 PTC patients ranged from 27 to 58, with an average score of 38.19 ± 6.68. Seven patients (6.54%) met the criteria for anxiety; the mean SAS score among these patients was 51.57 ± 2.88. The remaining 100 patients (93.46%) did not meet the criteria for anxiety; the mean SAS score among these patients was 37.04 ± 5.49. Among all participants, TSH levels varied from 0.30 to 5.09, with an average of 2.08 ± 0.91. Nine participants exhibited slight fluctuations in FT3, FT4, T3, T4, and TSH levels; these hormone levels consistently remained within the normal range for the other 98 patients. Linear correlation analysis revealed a significant positive correlation between anxiety and TSH levels (p < 0.001). Conclusion: The results demonstrated a significant positive correlation between anxiety and TSH levels in patients with PTC post-MWA, indicating that increased anxiety is associated with increased TSH levels.

SGLT2 inhibitor as a potential therapeutic approach in hyperthyroidism-induced cardiopulmonary injury in rats

Hyperthyroidism-induced cardiac disease is an evolving health, economic, and social problem affecting well-being. Sodium-glucose cotransporter protein 2 inhibitors (SGLT2-I) have been proven to be cardio-protective when administered in cases of heart failure. This study intended to investigate the potential therapeutic effect of SGLT2-I on hyperthyroidism-related cardiopulmonary injury, targeting the possible underlying mechanisms. The impact of the SGLT2-I, dapagliflozin (DAPA), (1 mg/kg/day, p.o) on LT4 (0.3 mg/kg/day, i.p)-induced cardiopulmonary injury was investigated in rats. The body weight, ECG, and serum hormones were evaluated. Also, redox balance, DNA fragmentation, inflammatory cytokines, and PCR quantification in heart and lung tissues were employed to investigate the effect of DAPA in experimentally induced hyperthyroid rats along with histological and immunohistochemical examination. Coadministration of DAPA with LT4 effectively restored all serum biomarkers to nearly average levels, improved ECG findings, and reinstated the redox balance. Also, DAPA could improve DNA fragmentation, elevate mtTFA, and lessen TNF-α and IGF-1 gene expression in both organs of treated animals. Furthermore, DAPA markedly improved the necro-inflammatory and fibrotic cardiopulmonary histological alterations and reduced the tissue immunohistochemical expression of TNF-α and caspase-3. Although further clinical and deep molecular studies are required before transposing to humans, our study emphasized DAPA's potential to relieve hyperthyroidism-induced cardiopulmonary injury in rats through its antioxidant, anti-inflammatory, and anti-apoptotic effects, as well as via antagonizing the sympathetic over activity.

Effect of extra-low dose levothyroxine supplementation on pregnancy outcomes in women with subclinical hypothyroidism undergoing in vitro fertilization and embryo transfer

OBJECTIVE

This study was undertaken to test the therapeutic effect of extra-low dose of levothyroxine (LT4; 25 mcg/day) to preconception and pregnant women with subclinical hypothyroidism (SCH).

MATERIALS AND METHODS

This is a retrospective study, SCH women who succeeded in their first in vitro fertilization (IVF) cycle between January 1, 2018, to December 31, 2020 were included. SCH is defined as normal serum free thyroxine (T4) level and an elevated serum thyroid stimulating hormone (TSH) level >4 mIU/L. Extra-low dose of levothyroxine (LT4; 25 mcg/day) was prescribed to the SCH women from the establish of diagnosis of SCH to the end of pregnancy. The pregnancy outcomes (miscarriage, live birth, preterm birth, and small for gestational age baby) were compared to the euthyroid pregnant women.

RESULTS

Totally, 589 women were screened, and 317 cases received their first time IVF treatment. 167 women were clinically pregnant after IVF treatment, 155 of them were euthyroid and 12 of these women were diagnosed to have SCH. The average age of the participants was 35 years old. There were no significant differences in age, body mass index (BMI), anti-müllerian hormone (AMH), types of embryo transfer, number of embryos to transfer, or embryo stage during transfer between two groups. The live birth rate, miscarriage rate, and preterm birth rate in women with SCH supplemented with extra-low dose of LT4 were non-inferior to euthyroid patients (miscarriage rate: P = 0.7112; live birth rate: P = 0.7028; preterm delivery: P = 0.2419; small for gestational age: P = 0.2419).

CONCLUSION

Our result demonstrated that supplementation with extra-low dose of levothyroxine at 25 mcg/day to SCH women can produce the comparable obstetrical and neonatal outcome as that in euthyroid pregnant women. Accordingly, we suggest extra-low-dose of levothyroxine may be considered as a safe and effective alternative for those SCH pregnant women who were not tolerated to the standard dose of levothyroxine.

Feasibility study on individualized management of postoperative patients with differentiated thyroid cancer based on internet and programming technology

PURPOSE

To explore the feasibility of individualized management of postoperative patients with differentiated thyroid cancer by a mode based on internet and programming technology.

METHODS

The enrolled patients were randomly divided into the study group and the control group. The study group used a mobile application to collect patient information, evaluate the risk of thyroid cancer recurrence and levothyroxine medication risk, develop individual thyrotropin control targets, and push levothyroxine adjustment recommendations to patients. In the control group, the traditional outpatient follow-up mode was used.

RESULTS

Two hundred patients were randomly divided into the study group and the control group at a 1:1 ratio. There was no significant difference in the physical and chemical indices between the two groups at baseline. During the 1-year follow-up, there was no significant difference in the thyrotropin attainment rate, heart rate or bone mineral density between the study group and the control group. During the 2-year follow-up, the thyrotropin attainment rate of the study group was better than that of the control group. The total score of Symptom Checklist 90 of the study group was lower than the control group, and satisfaction with the treatment was significantly higher than that of the control group.

CONCLUSION

The management based on the internet and programming technology is not inferior to the traditional outpatient follow-up mode, and is beneficial to improve patients' quality of life, promote the implementation of the national graded diagnosis and treatment system and the grassroots management of chronic diseases.

Non-Alcoholic Fatty Liver Disease: Translating Disease Mechanisms into Therapeutics Using Animal Models

Nonalcoholic fatty liver disease (NAFLD) is a range of pathologies arising from fat accumulation in the liver in the absence of excess alcohol use or other causes of liver disease. Its complications include cirrhosis and liver failure, hepatocellular carcinoma, and eventual death. NAFLD is the most common cause of liver disease globally and is estimated to affect nearly one-third of individuals in the United States. Despite knowledge that the incidence and prevalence of NAFLD are increasing, the pathophysiology of the disease and its progression to cirrhosis remain insufficiently understood. The molecular pathogenesis of NAFLD involves insulin resistance, inflammation, oxidative stress, and endoplasmic reticulum stress. Better insight into these molecular pathways would allow for therapies that target specific stages of NAFLD. Preclinical animal models have aided in defining these mechanisms and have served as platforms for screening and testing of potential therapeutic approaches. In this review, we will discuss the cellular and molecular mechanisms thought to contribute to NAFLD, with a focus on the role of animal models in elucidating these mechanisms and in developing therapies.

Association between sensitivity to thyroid hormones and risk of arrhythmia in patients with coronary heart disease: a RCSCD-TCM study in China

BACKGROUND

Thyroid dysfunction is closely related to arrhythmia. However, the relationship between sensitivity to thyroid hormone and risk of arrhythmia remains unknown. This study aimed to investigate the association between the thyroid system complex index and risk of arrhythmia in patients with coronary heart disease (CHD).

METHODS

This large, multicenter study included 28,413 patients with CHD. Central sensitivity to thyroid hormone was assessed by calculating the thyroid feedback quantile-based index (TFQI). Logistic regression was used to analyze the relationship between sensitivity to thyroid hormone and risk of arrhythmia. This study also assessed the relationship between sensitivity to thyroid hormone and risk of arrhythmia in different sexes, ages, and glucose regulation and blood lipid states.

RESULTS

Of the 28,413 participants, 8935 (31.4%) patients with CHD had arrhythmia. There was a remarkable association between TFQI and risk of arrhythmia (odds ratio [OR]: 0.783; 95% confidence interval [CI], 0.735-0.836). Furthermore, the association between the TFQI and risk of arrhythmia in women (OR: 0.731; 95% CI: 0.667-0.802) was stronger than that in men (OR: 0.894; 95% CI: 0.816-0.910), as well as higher in elder (OR: 0.779; 95% CI: 0.721-0.843) than middle-aged (OR: 0.789; 95% CI: 0.703-0.886) patients. Furthermore, the association was strong in the state of diabetes (OR: 0.635; 95% 0.569-0.709) and dyslipidemia (OR: 0.706; 95% CI: 0.644-0.774).

CONCLUSION

There is a remarkable association between sensitivity to thyroid hormone and risk of arrhythmia in patients with CHD, which is more pronounced among women and the elderly. The association is also stronger in CHD patients with dyslipidemia or diabetes.

Hormonal and inflammatory modulatory effects of hesperidin in hyperthyroidism-modeled rats

The goal of the current study was to investigate the hormonal modulatory efficiency of hesperidin, through its regulatory potential of immunological, inflammatory, and/or antioxidant changes in on hyperthyroidism modeled adult female albino rats. Both normal and hyperthyroidism modeled rats (140-160g) were randomly divided into four groups (10 animals each) as follows: 1) healthy animals were daily ingested with saline for six weeks, and served as control group, 2) healthy animals were intraperitoneally injected with hesperidin (50 mg/kg/day) for a similar period, 3) hyperthyroidism-modeled animals without any treatment acted as positive control, and 4) hyperthyroidism-modeled animals were treated intraperitoneally with hesperidin for a similar period. The findings showed that hesperidin significantly modulated hyperthyroidism deteriorations, this was evidenced by a remarkable decline in serum T4, FT4, T3, FT3, TNF-α, IL1β-, IL4-, IL-6, and IL-10 levels, with a minor increase in TSH and significant raise in CD4+ level. Similarly, valuable improvement was observed in the oxidative status; serum SOD, GPx, CAT, and GSH levels were dramatically enhanced, associated with remarkable drop in MDA and NO levels. Also, hesperidin demonstrated nephro-hepatoprotective and anti-atherogenic potential, this was achieved from the notable reduction in ALAT and ASAT activities as well as urea, creatinine, cholesterol, and triglyceride close to the corresponding values of healthy group. These findings were supported by histological and immunohistochemical ones that showed a notable decrease in the expression of the calcitonin antibody. In conclusion, hesperidin possesses anti-hyperthyroidism, immunoinflammatory regulatory, and antioxidant activities that evidenced from the improvement of physio-architecture of the thyroid gland, reduction of inflammation and restoration of the impaired oxidative stress. This effect might be mechanized through immunological, inflammatory, apoptotic, and/or antioxidant modulatory pathways.

Update on subclinical thyroid dysfunction

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Rare case of Torsades de Pointes in severe hypothyroidism: literature review and challenges in management

Background

Hypothyroidism can manifest as several important cardiac abnormalities. There are few reports of ventricular dysrhythmias (VDs) in hypothyroidism. We described a rare case of VDs in severe hypothyroidism and reviewed the literature behind its management.

Case presentation

A 67-year-old gentleman, with poor compliance to treatment for Hashimoto’s thyroiditis, presented with palpitations to the Emergency Department. He had runs of non-sustained ventricular tachycardia (NSVT). He was treated with intravenous (IV) amiodarone and admitted to the intensive care unit for observation. He then developed recurrent Torsades de Pointes (Tdp) despite treatment with several anti-arhythmics. He required electrical cardioversion and eventual transvenous overdrive pacing (OP). VT recurred while he was on OP. VT resolved and he was weaned off OP only after adequate thyroid hormone replacement.

Conclusions

VDs, including NSVT, Tdp, and VT, are rare and potentially lethal in hypothyroidism. Our case demonstrates important challenges in the management of severe hypothyroidism. Here, VDs are often refractory to treatment with drugs and electrical means. The choice(s) of anti-arrhthymics requires careful consideration and can be difficult before thyroid function tests are known. Amiodarone use should be cautioned as it is associated with thyroid dysfunction and QT interval prolongation.

There is no literature to guide thyroid hormone replacement in this disease. Aggressive replacement is associated with adverse cardiovascular effects. Our case showed a fine balance between the risk of rapid thyroid hormone replacement and the urgency to terminate VDs. Its administration should be carefully monitored amidst bridging strategies like electrical cardioversion and OP to manage life-threatening VDs.

Hypothyroidism and Risk of Cardiovascular Disease

Thyroid hormones (TH) have a significant impact on cellular oxidative metabolism. Besides that, they maintain vascular homeostasis by positive effects on endothelial and vascular smooth muscle cells. Subclinical (SCH) and clinical (CH) hypothyroidism influences target organs by changing their morphology and function and impaired blood and oxygen supply induced by accelerated atherosclerosis. The increased risk of acceleration and extension of atherosclerosis in patients with SCH and CH could be explained by dyslipidemia, diastolic hypertension, increased arterial stiffness, endothelial dysfunction, and altered blood coagulation. Instability of atherosclerotic plaque in hypothyroidism could cause excessive activity of the elements of innate immunity, which are characterized by the significant presence of macrophages in atherosclerotic plaques, increased nuclear factor kappa B (NFkB) expression, and elevated levels of tumor necrosis factor α (TNF-α) and matrix metalloproteinase (MMP) 9, with reduced interstitial collagen; all of them together creates inflammation milieu, resulting in plaque rupture. Optimal substitution by levothyroxine (LT4) restores biochemical euthyroidism. In postmenopausal women and elderly patients with hypothyroidism and associated vascular comorbidity, excessive LT4 substitution could lead to atrial rhythm disorders and osteoporosis. Therefore, it is of interest to maintain thyroid-stimulating hormone (TSH) levels in the reference range, thus eliminating the deleterious effects of lower or higher TSH levels on the cardiovascular system. This review summarizes the recent literature on subclinical and clinical hypothyroidism and atherosclerotic cardiovascular disease and discusses the effects of LT4 replacement therapy on restoring biochemical euthyroidism and atherosclerosis processes.