Beta-adrenergic blockade for the treatment of hyperthyroidism

Toxic Thyroid Adenoma Presenting as Apathetic Hyperthyroidism: A Case Report

The thyroid gland is an essential endocrine organ that secretes hormones to regulate homeostasis across multiple organ systems throughout the body. It is actively regulated by the hypothalamic-pituitary-thyroid (HPT) axis, where negative feedback modulates the amounts of active hormone being released; thus, lesions that disrupt the proper functioning of this gland or its regulatory mechanisms can be destructive. Toxic thyroid adenomas are usually singular benign functioning nodules in the thyroid gland that cause thyrotoxicosis. Hyperthyroidism is commonly clinically silent, however, in most symptomatic cases, patients will be diagnosed based on abnormal laboratory findings and typical hyperthyroid symptoms. This case report examines an 81-year-old male with an extensive medical history who presented with complaints of new-onset generalized fatigue coupled with bilateral lower extremity muscle cramps. A positron emission tomography (PET) scan for other medical conditions incidentally noted mildly increased uptake in the thyroid gland, prompting a further investigation that resulted in a diagnosis of toxic thyroid adenoma. The patient responded well to treatment with methimazole and has remained in a euthyroid state.

Atrioventricular block in patients with hyperthyroidism: a narrative review

Atrioventricular block (AVB) is a rare cardiac manifestation of hyperthyroidism (HTH). The scientific literature contains multiple reports of AVB in patients with HTH, ranging from subclinical to overt HTH and even thyroid storm. However, much remains unknown about the true prevalence, clinical course, optimal management, and outcomes of AVB in patients with HTH. Such patients are possibly overtreated with pacemakers because of a lack of understanding that AVB might be secondary to the hyperthyroid state and thus reversible. This narrative review discusses the pathophysiology of AVB in patients with HTH in the context of the available evidence.

Investigating the effect of Shenmai injection on cardiac electrophysiology and calcium signaling using human-induced pluripotent stem cell-derived cardiomyocytes

Traditional Chinese medicine injection (TCMI) refers to the use of modern technology to make Chinese patent medicines in injectable forms, which shorten the onset time of the traditional Chinese medicine (TCM). Although there have been clinical cases in which Shenmai injection (SMI) was used to treat cardiovascular diseases (CVDs), there are no pharmacological experiments that investigate the efficacy of the drug in vitro or the underlying mechanisms.

Aim of the study

We aimed to systemically evaluate the efficacy and investigate the mechanisms of SMI in modulating electrophysiology and calcium (Ca²⁺) signaling using a microelectrode array (MEA) and a genetically encoded Ca²⁺ indicator, GCaMP6s, respectively, in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).

Materials and methods

A MEA system was employed to record field potentials (FPs) in hiPSC-CMs. The QT interval is corrected by the RR interval, the reciprocal of the beating rate. GCaMP6s was used to measure Ca²⁺ signaling in hiPSC-CMs. Meanwhile, the transcriptome changes in hiPSC-CMs treated with 2% SMI were examined using RNAseq. In addition, the ingredients of SMI were investigated using liquid chromatography-mass spectrometry (LC-MS).

Results

It was found that 0.5%, 1%, and 2% (v/v) SMIs could increase corrected QT (QTc) but did not change other FP parameters. GCaMP6s was successfully applied to measure the chronic function of SMI. The full width at half maximum (FWHM), rise time, and decay time significantly decreased after treatment with SMI for 1 h and 24 h, whereas an increased Ca²⁺ transient frequency was observed.

Conclusions

We first used the Ca²⁺ indicator to measure the chronic effects of TCM. We found that SMI treatment can modulate electrophysiology and calcium signaling and regulate oxidative phosphorylation, cardiac muscle contraction, and the cell cycle pathway in hiPSC-CMs.

Clinical Review and Update on the Management of Thyroid Storm

Thyroid storm is a severe manifestation of thyrotoxicosis. Thyroid storm is diagnosed as a combination of thyroid function studies showing low to undetectable thyroid stimulating hormone (TSH) (<0.01mU/L) with elevated free thyroxine (T4) and/or triiodothyronine (T3), positive thyroid receptor antibody (TRab) (if Graves' disease is the underlying etiology), and with clinical signs and symptoms of end organ damage. Treatment involves bridging to a euthyroid state prior to total thyroidectomy or radioactive iodine ablation to limit surgical complications such as excessive bleeding from highly vascular hyperthyroid tissue or exacerbation of thyrotoxicosis. The purpose of this article is a clinical review of the various treatments and methodologies to achieve a euthyroid state in patients with thyroid storm prior to definitive therapy.

Resolution of Thyrotoxicosis-Associated Pulmonary Hypertension With Treatment of Thyrotoxicosis: A Case-Based Report and Literature Review

We present a case of a 41-year-old Afro-Caribbean female, who was diagnosed with thyrotoxic Graves’ disease. She had a past medical history of hypertension and was on amlodipine and valsartan. There was no significant family history of note. She initially presented to Emergency Department with palpitations and excessive sweating. Her thyroid-stimulating hormone was <0.02mu/L and free triiodothyronine (T3) 29.5pmol/L at the time of diagnosis. The thyroid peroxidase antibody test was negative. She was started on carbimazole 15mg once daily and propranolol 40mg twice daily. She remained non-compliant to treatment for over two years and missed most outpatient clinic appointments and her condition remained poorly controlled during this time period. She was re-admitted to the hospital after 18 months, with high output congestive cardiac failure. An echocardiogram showed pulmonary hypertension and her right ventricular systolic pressure was measured to be 70-75mmHg. She was started on Lugol's iodine 0.2mls three times daily, propranolol 40mg three times daily, cholestyramine 4 gram four times a day, propylthiouracil 100mg four times a day. After 3 weeks of treatment, she became euthyroid and her pulmonary hypertension improved dramatically with treatment. She underwent total thyroidectomy after a few weeks and biopsies confirmed the findings of Graves’ disease. 

Cardiovascular Involvement in Thyrotoxicosis Resulting in Heart Failure: The Risk Factors and Hemodynamic Implications

Thyrotoxicosis is a clinical syndrome with persistently elevated concentrations of free triiodothyronine, free thyroxine, or both, which correlates with an increased thyroid metabolic function. This article has discussed the direct effect of increased thyroid hormone on the heart, as the thyroid hormone physiologically exhibits a close harmony with hormones of the cardiovascular system. This action can lead to disturbances in hemodynamic stability, exacerbating the possibility of developing complications such as heart failure and life-threatening arrhythmias. This article has also explored the multifaceted pathogenesis of thyrotoxicosis and various pharmacological treatment options, including beta-blockers and anti-thyroid drugs. This article has reviewed numerous studies that have concluded that the main goal of therapy should always aim to normalize thyroid hormone levels based on the etiology of the thyrotoxicosis, although cardiovascular conditions are associated with a higher rate of mortality.

Acute effect of propranolol on resting energy expenditure in hyperthyroid patients

OBJECTIVE

Hyperthyroidism is a common endocrine disorder which leads to higher resting energy expenditure (REE). Increased activity of brown adipose tissue (BAT) contributes to elevated REE in hyperthyroid patients. For rapid control of hyperthyroid symptoms, the non-selective β-blocker propranolol is widely used. While, long-term treatment with propranolol reduces REE it is currently unclear whether it can also acutely diminish REE.

DESIGN

In the present prospective interventional trial we investigated the effect of propranolol on REE in hyperthyroid patients.

METHODS

Nineteen patients with overt primary hyperthyroidism were recruited from the endocrine outpatient clinic. REE was measured by indirect calorimetry before and after an acute dose of 80mg propranolol and during a control period, respectively. Additionally, skin temperature was recorded at eleven predefined locations during each study visit, vital signes and heart rate (HR) were measured before and after administration of propranolol.

RESULTS

Mean REE decreased slightly after acute administration of 80mg propranolol (p= 0.03) from 1639 ± 307 kcal/24h to 1594 ± 283 kcal/24h. During the control visit REE did not change significantly. HR correlated significantly with the level of free T3 (R² = 0.38, p=0.029) free T4 (R² = 0.39, p=0.026). HR decreased 81 ± 12 bpm to 67 ± 7.6 bpm 90 minutes after oral administration of propranolol (p<0.0001). Skin temperature did not change after propranolol intake.

CONCLUSIONS

In hyperthyroid patients a single dose of propranolol reduced heart rate substantially but REE diminished only marginally probably due to reduced myocardial energy consumption. Our data speak against a relevant contribution of BAT to the higher REE in hyperthyroidism.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier (NCT03379181).

Beneficial Extracardiac Effects of Cardiovascular Medications

Cardiovascular diseases are the most common cause of death worldwide, with cardiovascular medications being amongst the most common medications prescribed. These medications have diverse effects on the heart, vascular system, as well as other tissues and organ systems. The extra cardiovascular effects have been found to be of use in the treatment of non-cardiovascular diseases and pathologies. Minoxidil is used to manage systemic hypertension with its well-known side effect of hirsutism used to treat alopecia and baldness. Sildenafil was originally investigated as a treatment option for systemic hypertension; however, its side effect of penile erection led to it being widely used for erectile dysfunction. Alpha-1 blockers such as terazosin are indicated to treat systemic hypertension but are more commonly used for benign prostatic hyperplasia and post-traumatic stress disorder. Beta blockers are the mainstay treatment for congestive heart failure and systemic hypertension but have been found useful to help in patients with intention tremors as well as prophylaxis of migraines. Similarly, calcium channel blockers are indicated in medical expulsion therapy for ureteric calculi in addition to their cardiovascular indications. Thiazides are commonly used for treating systemic hypertension and as diuretics. Thiazides can cause hypocalciuria and hypercalcemia. This side effect has led to thiazides being used to treat idiopathic hypercalciuria and associated nephrolithiasis. Spironolactone is commonly utilized in treating heart failure and as a diuretic for edema. It's well described anti-androgen side effects have been used for acne vulgaris and hirsutism in polycystic ovarian syndrome. This review article discusses how the various extracardiovascular effects of commonly used cardiovascular medications are put to use in managing non-cardiovascular conditions.

A case report of new onset graves' disease induced by SARS-CoV-2 infection or vaccine?

The virus responsible for the COVID-19 pandemic continues to pose unmatched challenges in the world. It can cause systemic inflammation, which can lead to multiorgan involvement and subsequent damage. The relationship that possibly exists between the COVID-19 infection, the newly developed vaccines, and thyroid disease are still under extensive investigation. We are reporting the first case of new-onset graves’ disease in a young, healthy man after COVID-19 infection and receiving a COVID-19 vaccine dose.

Treatment of Grave’s Disease in Adults

Graves disease is an autoimmune disease, with a genetic susceptibility, activated by environmental factors like stress, iodine excess, infections, pregnancy and smoking. It is caused by thyroid stimulating immunoglobulin (TSI) or thyroid stimulating antibody (TSAb) and is the most common cause of hyperthyroidism with an incidence of 21 per 100,000 per year. Treatment of Graves disease includes antithyroid drugs such as methimazole and propylthiouracil, radioactive iodine therapy and thyroidectomy. Methimazole, an antithyroid drug that belongs to the thioamides class, is usually the first line of treatment due to lower risk of hepatotoxicity compared to propylthiouracil. Radioactive iodine therapy is reserved for those patients who do not respond to antithyroid drugs or have contraindication or adverse effects generated by antithyroid drugs, and thyroid surgery is an option in people with thyroid nodular disease with suspected malignancy or large goiters such as predictors of poor response to antithyroid drugs and radioactive iodine therapy. Multiple factors influence the management of patients with Graves disease including patient and physician preferences, access to medical services and patients features such as age, complications and comorbidities.

A new perspective on cardiovascular drift during prolonged exercise

Prolonged exercise induces cardiovascular drift, which is characterized by decreasing mean arterial pressure (MAP), stroke volume and heart rate increase. Cardiovascular drift has been debated for a long time. Although the exact mechanisms underlying cardiovascular drift are still unknown, two theories have been proposed. The first is that increased skin blood flow displaces blood volume from central circulation to the periphery, which reduces stroke volume. According to this theory, the rise in heart rate is presumably responding to the drop in stroke volume and MAP. The alternative theory is that an increase in heart rate is due to an increase in sympathetic nervous activity causing reducing time at diastole, and therefore stroke volume. It may be difficult to determine a single robust factor accounting for cardiovascular drift, due to the broad range of circumstances. The primary focus of this review is to elucidate our understanding of cardiovascular drift during prolonged exercise through nitric oxide and force-frequency relationship. We highlight for the very first time that cardiovascular drift (in some conditions and within a specific time period) may be considered as a protective strategy against potential damage that could be induced by the intense and prolonged contraction of the myocardium.

Medical treatment of thyrotoxicosis

Medical treatment is the primary therapeutic option for thyrotoxicosis/hyperthyroidism. Two groups of causes of thyrotoxicosis (i.e. thyrotoxicosis with hyperthyroidism and thyrotoxicosis without hyperthyroidism) need to be considered for therapeutic reasons. Herein we provide an updated review on the role of conventional medical therapies (i.e. β-blockers, antithyroid drugs [ATDs], corticosteroids, inorganic iodide, perchlorate, cholecystographic agents, lithium, cholestyramine) in the main causes of thyrotoxicosis, starting from the rationale subtending their clinical application.

Graves' disease

Graves' disease (GD) is an autoimmune disease that primarily affects the thyroid gland. It is the most common cause of hyperthyroidism and occurs at all ages but especially in women of reproductive age. Graves' hyperthyroidism is caused by autoantibodies to the thyroid-stimulating hormone receptor (TSHR) that act as agonists and induce excessive thyroid hormone secretion, releasing the thyroid gland from pituitary control. TSHR autoantibodies also underlie Graves' orbitopathy (GO) and pretibial myxoedema. Additionally, the pathophysiology of GO (and likely pretibial myxoedema) involves the synergism of insulin-like growth factor 1 receptor (IGF1R) with TSHR autoantibodies, causing retro-orbital tissue expansion and inflammation. Although the aetiology of GD remains unknown, evidence indicates a strong genetic component combined with random potential environmental insults in an immunologically susceptible individual. The treatment of GD has not changed substantially for many years and remains a choice between antithyroid drugs, radioiodine or surgery. However, antithyroid drug use can cause drug-induced embryopathy in pregnancy, radioiodine therapy can exacerbate GO and surgery can result in hypoparathyroidism or laryngeal nerve damage. Therefore, future studies should focus on improved drug management, and a number of important advances are on the horizon.

Cardiorespiratory Failure in Thyroid Storm: Case Report and Literature Review

Thyroid storm is a potentially fatal manifestation of thyrotoxicosis. Cardiopulmonary failure is the most common cause of death in thyroid storm. Clinicians should keep in mind that thyroid storm complicated with cardiopulmonary failure can be the first presentation of thyrotoxicosis. As early intervention is associated with improved patient outcome, prompt diagnosis based on clinical grounds is of paramount importance in the management of thyrotoxicosis. A high index of suspicion and the ability of early recognition of impending thyroid storm depends on a thorough knowledge of both the typical and atypical clinical features of this illness. Herein, we report a case of thyroid storm presenting as cardiopulmonary failure in a 51-year-old woman with undiagnosed Grave’s disease. Additionally, we review the pathophysiology of cardiopulmonary failure associated with thyrotoxicosis and various treatment modalities for thyroid storm.

Hypothalamic effects of thyroid hormone

Thyroid hormone (TH) is a key driver of metabolism in mammals. Plasma concentrations of TH are kept within a narrow range by negative feedback regulation in the hypothalamus-pituitary-thyroid (HPT) axis. Plasma TH concentrations are an important determinant of metabolic processes in liver and brown adipose tissue (BAT). In addition to endocrine effects of TH derived from the circulation, recent studies have demonstrated additional neural routes for intrahypothalamic thyroid hormone to regulate metabolism in liver and BAT via the sympathetic and parasympathetic branch of the autonomic nervous system (ANS). This review provides an overview of studies reporting metabolic effects of selective administration of T3 within hypothalamic nuclei including the paraventricular nucleus (PVN), the ventromedial nucleus (VMH), the arcuate nucleus (Arc), and the anterior hypothalamic area (AHA). This overview of the literature suggests that intrahypothalamic T3 can have profound effects on hepatic glucose production and insulin sensitivity, energy expenditure in BAT, cardiovascular function and feeding behavior. As the experiments have been performed in experimental animals exclusively, and the timing and route of T3 administration may be an important determinant of effect size, the clinical relevance of these metabolic effects in the chronic setting remains to be established.

Thyroid dysfunction in the severely ill and elderly

Preview Manifestations of thyroid dysfunction may be totally misleading in severely ill and elderly patients, often confounding clinical diagnosis. To prevent undue morbidity and mortality in these patients, appropriate selection and accurate interpretation of thyroid function tests are crucial. In this article, Dr Isley compares the classic signs and symptoms of thyroid disorders with those that may appear in elderly patients and in patients severely ill with other diseases, and he presents algorithms for diagnosing thyrotoxicosis and hypothyroidism.

Thyroid Crisis in a Patient With Burn Injury

Thyroid crisis is an exacerbation of hyperthyroidism that results in severe systemic disturbances and could be fatal. Similarly, severe burn injury also has a hypermetabolic response as part of its presentation. When these two conditions are present concurrently, one must be cognizant that the patient requires urgent optimization of their hyperthyroid status before surgery, and continuous monitoring in an intensive care unit setting. We offer a systematic approach to managing these patients.

Echocardiographic assessment of left ventricular function in thyrotoxicosis and implications for the therapeutics of thyrotoxic cardiac disease

INTRODUCTION

Thyrotoxicosis is an endocrine disorder with prominent cardiovascular manifestations. Thyroid hormone acts through genomic and non-genomic mechanisms to regulate cardiac function. Echocardiography is a useful, non-invasive, easily accessible, and affordable tool for studying the structural and physiological function of the heart.

AIM

We studied thyrotoxicosis patients in a Nigerian Teaching Hospital and employed trans-thoracic echocardiography to find out if there were abnormalities in the hearts of these patients.

METHODS

Fifty adult thyrotoxicosis patients diagnosed with clinical and thyroid function tests in the medical out-patient unit of the hospital were recruited and we performed transthoracic echocardiography with a Sonos 2000 HP machine.

RESULTS

We documented the presence of abnormalities in the following proportion of thyrotoxicosis patients: left ventricular enhanced systolic function in 30%, enhanced diastolic function in 34%, diastolic dysfunction in 34%, heart failure with preserved ejection fraction in10%, heart failure with reduced ejection fraction in 6%, and left ventricular hypertrophy in 34%.

CONCLUSION

Echocardiography was useful in the stratification of cardiac function abnormalities and is indispensable as a guide in the choice of therapeutic options in patients with thyrocardiac disease. The finding of left ventricular enhanced systolic and diastolic functions signify early echocardiographic detectable cardiac abnormalities in thyrotoxicosis, and the clinical management includes the use of anti-thyroid drugs and β-adrenoceptor blockade. Diastolic dysfunction in thyrotoxicosis patients asymptomatic for cardiac disease should be treated with anti-thyroid drugs, and β-adrenoceptor blockade. The judicious application of clinical therapeutics will guide the use of anti-thyroid drugs, diuretics, digoxin, angiotensin inhibitors, and β-adrenoceptor blockade in the successful management of thyrotoxicosis patients with heart failure and reduced, preserved, or increased ejection fraction: parameters which are derived from echocardiography.

Thyroid hormone interacts with the sympathetic nervous system to modulate bone mass and structure in young adult mice

To investigate whether thyroid hormone (TH) interacts with the sympathetic nervous system (SNS) to modulate bone mass and structure, we studied the effects of daily T3 treatment in a supraphysiological dose for 12 wk on the bone of young adult mice with chronic sympathetic hyperactivity owing to double-gene disruption of adrenoceptors that negatively regulate norepinephrine release, α(2A)-AR, and α(2C)-AR (α(2A/2C)-AR(-/-) mice). As expected, T3 treatment caused a generalized decrease in the areal bone mineral density (aBMD) of WT mice (determined by DEXA), followed by deleterious effects on the trabecular and cortical bone microstructural parameters (determined by μCT) of the femur and vertebra and on the biomechanical properties (maximum load, ultimate load, and stiffness) of the femur. Surprisingly, α(2A/2C)-AR(-/-) mice were resistant to most of these T3-induced negative effects. Interestingly, the mRNA expression of osteoprotegerin, a protein that limits osteoclast activity, was upregulated and downregulated by T3 in the bone of α(2A/2C)-AR(-/-) and WT mice, respectively. β1-AR mRNA expression and IGF-I serum levels, which exert bone anabolic effects, were increased by T3 treatment only in α(2A/2C)-AR(-/-) mice. As expected, T3 inhibited the cell growth of calvaria-derived osteoblasts isolated from WT mice, but this effect was abolished or reverted in cells isolated from KO mice. Collectively, these findings support the hypothesis of a TH-SNS interaction to control bone mass and structure of young adult mice and suggests that this interaction may involve α2-AR signaling. Finally, the present findings offer new insights into the mechanisms through which TH regulates bone mass, structure, and physiology.

The Brazilian consensus for the diagnosis and treatment of hyperthyroidism: recommendations by the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism

INTRODUCTION

Hyperthyroidism is characterized by increased synthesis and release of thyroid hormones by the thyroid gland. Thyrotoxicosis refers to the clinical syndrome resulting from excessive circulating thyroid hormones, secondary to hyperthyroidism or due to other causes. This article describes evidence-based guidelines for the clinical management of thyrotoxicosis.

OBJECTIVE

This consensus, developed by Brazilian experts and sponsored by the Department of Thyroid Brazilian Society of Endocrinology and Metabolism, aims to address the management, diagnosis and treatment of patients with thyrotoxicosis, according to the most recent evidence from the literature and appropriate for the clinical reality of Brazil.

MATERIALS AND METHODS

After structuring clinical questions, search for evidence was made available in the literature, initially in the database MedLine, PubMed and Embase databases and subsequently in SciELO - Lilacs. The strength of evidence was evaluated by Oxford classification system was established from the study design used, considering the best available evidence for each question.

RESULTS

We have defined 13 questions about the initial clinical approach for the diagnosis and treatment that resulted in 53 recommendations, including the etiology, treatment with antithyroid drugs, radioactive iodine and surgery. We also addressed hyperthyroidism in children, teenagers or pregnant patients, and management of hyperthyroidism in patients with Graves' ophthalmopathy and various other causes of thyrotoxicosis.

CONCLUSIONS

The clinical diagnosis of hyperthyroidism usually offers no difficulty and should be made with measurements of serum TSH and thyroid hormones. The treatment can be performed with antithyroid drugs, surgery or administration of radioactive iodine according to the etiology of thyrotoxicosis, local availability of methods and preferences of the attending physician and patient.

Management of Graves' disease: an overview and comparison of clinical practice guidelines with actual practice trends

Over the last century, much has been learned about the pathogenesis, manifestations, and management of Graves' disease leading to the establishment of evidence-based clinical practice guidelines. The joint clinical practice guidelines from the American Thyroid Association and the American Association of Clinical Endocrinologists give recommendations on both the diagnosis and treatment of hyperthyroidism. A survey of clinicians performed that same year, however, revealed that current practices diverge from these recently published guidelines in multiple areas. These differences will need to be assessed serially to determine the impact of the guidelines on future clinical practice and perhaps vice versa.

β1-Adrenergic receptor signaling activates the epithelial calcium channel, transient receptor potential vanilloid type 5 (TRPV5), via the protein kinase A pathway

Epinephrine and norepinephrine are present in the pro-urine. β-Adrenergic receptor (β-AR) blockers administered to counteract sympathetic overstimulation in patients with congestive heart failure have a negative inotropic effect, resulting in reduced cardiac contractility. Positive inotropes, β1-AR agonists, are used to improve cardiac functions. Active Ca(2+) reabsorption in the late distal convoluted and connecting tubules (DCT2/CNT) is initiated by Ca(2+) influx through the transient receptor potential vanilloid type 5 (TRPV5) Ca(2+) channel. Although it was reported that β-ARs are present in the DCT2/CNT region, their role in active Ca(2+) reabsorption remains elusive. Here we revealed that β1-AR, but not β2-AR, is localized with TRPV5 in DCT2/CNT. Subsequently, treatment of TRPV5-expressing mouse DCT2/CNT primary cell cultures with the β1-AR agonist dobutamine showed enhanced apical-to-basolateral transepithelial Ca(2+) transport. In human embryonic kidney (HEK293) cells, dobutamine was shown to stimulate cAMP production, signifying functional β1-AR expression. Fura-2 experiments demonstrated increased activity of TRPV5 in response to dobutamine, which could be prevented by the PKA inhibitor H89. Moreover, nonphosphorylable T709A-TRPV5 and phosphorylation-mimicking T709D-TRPV5 mutants were unresponsive to dobutamine. Surface biotinylation showed that dobutamine did not affect plasma membrane abundance of TRPV5. In conclusion, activation of β1-AR stimulates active Ca(2+) reabsorption in DCT2/CNT; an increase in TRPV5 activity via PKA phosphorylation of residue Thr-709 possibly plays an important role. These data explicate a calciotropic role in addition to the inotropic property of β1-AR.

Pitting type of pretibial edema in a patient with silent thyroiditis successfully treated by angiotensin II receptor blockade

Patient: Female, 56

Final Diagnosis: Thyroiditis – silent

Symptoms: Palpitations • pretibial pitting edema • short of breath • sweating

Medication: —

Clinical Procedure: —

Specialty: Endocrinology and Metabolic

Cardio-selective beta-blocker: pharmacological evidence and their influence on exercise capacity

For the past 40 years, beta-blockers have been widely used in cardiovascular medicine, reducing morbidity as well as mortality. Beta-blockers are currently used in a number of cardiovascular conditions such as systolic heart failure, postmyocardial infarction, and in prevention and treatment of arrhythmias. They are not recommended as the first line antihypertensive therapy, particularly in the elderly, unless there are specific indications. Despite the benefits of beta-blockers, tolerability concerns in patients with co-morbidities have limited their use. Some of these problems were overcome with the discovery of cardioselective beta-blockers. The third generation beta-blockers have additional properties of vasodilatation and advantages in terms of minimizing the adverse effects of beta-blockers. Some of the advantages include improvement of insulin resistance, decrease in cholesterol as well as alleviation of erectile dysfunction. Acute treatment with beta-blockers modifies local muscular metabolic properties and impairs endurance exercise capacity whereas the influence of chronic is debated controversially.

Ventricular fibrillation associated with early repolarization in a patient with thyroid storm

We present a case of a 69-year-old male who was hospitalized for the treatment of thyroid storm due to Grave's disease, who presented with unexpected ventricular fibrillation (VF). The possible etiology was early repolarization (ER), characterized by J-point elevation in inferior and posterolateral leads, unmasked by the attenuation of beta-adrenergic effect with normalization of thyroid hormones and following the administration of a beta-blocker. Our case focuses attention on the occurrence of VF in a patient with ER during the treatment of hyperthyroidism, which to our knowledge is the first such report.

Impact of thyroid function and polymorphisms in the type 2 deiodinase on blood pressure: the Rotterdam Study and the Rotterdam Scan Study

INTRODUCTION

Thyroid function and genetic variation in the hypothalamus-pituitary-thyroid axis have been implicated in blood pressure regulation and susceptibility to hypertension. However studies conducted thus far were small with controversial results.

OBJECTIVE

To examine whether serum thyroid parameters and polymorphisms in the type 2 deiodinase and the TSH receptor are associated with blood pressure and the presence of hypertension in two large cohorts of elderly subjects.

DESIGN AND PARTICIPANTS

We studied a random sample of 1444 subjects of the Rotterdam study, and 997 subjects of the Rotterdam Scan study, two population-based cohort studies among elderly individuals aged 55-90 years. Outcome measurements Data on blood pressure and hypertension were obtained, and serum thyroid parameters, D2-Thr92Ala, D2-ORFa-Gly3Asp and TSHR-Asp727Glu polymorphisms were determined.

RESULTS

In contrast to previous findings, no consistent and/or significant associations were found between serum TSH and FT4 and blood pressure in both cohorts. In addition, the D2-Thr92Ala, D2-ORFa-Gly3Asp and TSHR-Asp727Glu polymorphisms were not associated with blood pressure or the risk of hypertension.

CONCLUSIONS

In two large populations of elderly subjects, neither serum thyroid parameters nor polymorphisms in the type 2 deiodinase and the TSH receptor, were associated with blood pressure or the presence of hypertension. Our data suggest that thyroid function is not an important determinant of hypertension in elderly Dutch subjects.

Treatment of Graves' hyperthyroidism: evidence-based and emerging modalities

Currently there are three well-established treatment options for hyperthyroid Graves' disease (GD): antithyroid drug therapy with thionamides (ATD), radioactive iodine treatment with (131)I, and thyroid surgery. This article reviews the current evidence so the reader can evaluate advantages and disadvantages of these treatment modalities. Surgery is rarely used, except for patients who have a large goiter or ophthalmopathy. Fewer than 50% of patients treated with ATD remain in long-term remission. Therefore, radioactive iodine is used increasingly. No data as yet support the routine use of biologic therapies (eg, rituximab). Prospective, randomized studies comparing available and any novel therapeutic options for GD are needed. The focus of these studies should include, but not be limited to, cost and quality of life.

Hyperthyroid heart disease

The heart is an organ sensitive to the action of thyroid hormone, and measurable changes in cardiac performance are detected with small variations in thyroid hormone serum concentrations. Most patients with hyperthyroidism experience cardiovascular manifestations, and the most serious complications of hyperthyroidism occur as a result of cardiac involvement. Recent studies provide important insights into the molecular pathways that mediate the action of thyroid hormone on the heart and allow a better understanding of the mechanisms that underlie the hemodynamic and clinical manifestations of hyperthyroidism. Several cardiovascular conditions and drugs can interfere with thyroid hormone levels and may pose a difficulty in interpretation of laboratory data in patients with suspected thyroid heart disease. The focus of this report is a review of the current knowledge of thyroid hormone action on the heart and the clinical and hemodynamic laboratory findings as well as therapeutic management of patients with hyperthyroid heart disease.

Feline Thyroid Storm

Thyroid storm is a syndrome described in human medicine to define a multisystemic disorder resulting from organ exposure to excessive levels of thyroid hormone. This form of acute thyrotoxicosis, although uncommon, can be life threatening and is a significant cause of mortality in human emergency rooms. Although thyroid storm is a well-recognized clinical entity in human medicine, it has not been described in veterinary medicine. This article discusses the human syndrome and defines a similar syndrome in hyperthyroid veterinary patients. The clinical signs of and treatment modalities for feline thyroid storm are also presented.

Comparative effectiveness of carvedilol and propranolol on glycemic control and insulin resistance associated with l-thyroxin-induced hyperthyroidism — an experimental study

The present study was undertaken to investigate the effectiveness of adrenergic antagonists carvedilol and propranolol on l-thyroxin-induced cardiovascular and metabolic disturbances in rats. Treatment with l-thyroxin sodium (75 mg/kg body mass, s.c., every alternate day for 3 weeks), produced a significant increase in food and water intake, body temperature, heart rate, systolic blood pressure, along with an increase in serum T3, T4, and triglyceride levels. Besides a significant reduction in body mass, serum levels of TSH and cholesterol were also reduced following l-thyroxin treatment. Carvedilol (10 mg/kg body mass, orally) and propranolol (10 mg/kg body mass, i.p.) administered daily in the third week to 2 separate groups of l-thyroxin-treated animals reversed thyroxin-induced loss in body mass and rise in body temperature, blood pressure, and heart rate. Propranolol treatment increased TSH levels and decreased T3 and T4 levels in hyperthyroid animals, whereas carvedilol did not produce any effect on thyroid hormones. Carvedilol treatment reversed thyroxin induced hypertriglyceridemia, whereas propranolol treatment had no effect. Both carvedilol and propranolol prevented decrease in cholesterol levels induced by thyroxine. Compared with normal animals, l-thyroxin-treated animals showed a state of hyperglycemia, hyperinsulinaemia, impaired glucose tolerance, and insulin resistance, as inferred from elevated fasting serum glucose and insulin levels, higher area under the curve over 120 min for glucose, and decreased insulin sensitivity index (KITT). Propranolol and carvedilol treatment significantly decreased fasting serum glucose levels. Treatment with propranolol did not alter serum insulin levels, area-under-the-curve glucose, or KITT values. However, treatment with carvedilol significantly reduced area-under-the-curve glucose, decreased fasting serum insulin levels and significantly increased KITT values. In conclusion, carvedilol appears to produce favorable effects on insulin sensitivity and glycemic control and can therefore be considered as more efficacious adjunctive treatment than propranolol in hyperthyroidism.

Répercussions cardiaques des dysthyroïdies avérées

KEY POINTS

Thyroid hormones affect the vascular system, including the diastolic and systolic functioning of the heart. Resting heart rate increases early in hyperthyroidism (cardiac contractility expands due to improved ventricular loading and decreased systemic vascular resistance). Paradoxically, these hemodynamic alterations progressively reduce cardiac performance on effort (changes in diastolic, then systolic functioning) and finally at rest (modification in ventricular loading following tachycardia or atrial fibrillation), especially in cases of underlying heart disease (in the elderly). Hypothyroidism has an inverse hemodynamic effect and is less noisy, usually limited to relative bradycardia. The morbidity and mortality associated with hypothyroidism are apparently related to the atherogenic and prothrombotic vascular modifications that follow thyroid hormone deficiency, whereas heart failure and particularly atrial fibrillation and its thromboembolic complications are the primary consequences of hyperthyroidism. In both cases, return to normal thyroid levels corrects the cardiac abnormalities caused by the dysthyroidism. Dysthyroidism (hypo- or hyperthyroidism) occurs in 10 to 20% of the patients treated with amiodarone for arrhythmia. Because of its potential seriousness, some clinical or laboratory tests are necessary before initiating treatment, and specific clinical surveillance should be scheduled, including laboratory tests.

Hyperthyroidism: advantages and disadvantages of medical therapy

The most common causes of hyperthyroidism are Graves' disease, toxic nodular goiter, and iodine-induced hyperthyroidism. Hyperthyroidism can be treated medically with antithyroid drugs or radioactive iodine, or surgically. Multiple clinical factors must be weighed when choosing a treatment modality. All of the available forms of therapy have advantages and disadvantages, and treatment choices must be individualized.

Hyperthyroidism

Hyperthyroidism is a pathological syndrome in which tissue is exposed to excessive amounts of circulating thyroid hormone. The most common cause of this syndrome is Graves' disease, followed by toxic multinodular goitre, and solitary hyperfunctioning nodules. Autoimmune postpartum and subacute thyroiditis, tumours that secrete thyrotropin, and drug-induced thyroid dysfunction, are also important causes. The diagnosis of hyperthyroidism is generally straightforward, with raised serum thyroid hormones and suppressed serum thyrotropin in almost all cases. Appropriate treatment of hyperthyroidism relies on identification of the underlying cause. Antithyroid drugs, radioactive iodine, and surgery are the traditional treatments for the three common forms of hyperthyroidism. Beta-adrenergic blocking agents are used in most patients for symptomatic relief, and might be the only treatment needed for thyroiditis, which is transient. The more unusual causes of hyperthyroidism, including struma ovarii, thyrotropin-secreting tumours, choriocarcinoma, and amiodarone-induced thyrotoxicosis are, more often than not, a challenge to diagnose and treat.

Diagnosis and treatment of Graves disease

OBJECTIVE

To review the etiology, diagnosis, and clinical presentation of Graves disease and provide an overview of the standard and adjunctive treatments. Specifically, antithyroid drugs, beta-blockers, inorganic iodide, lithium, and radioactive iodine are discussed, focusing on current controversies.

DATA SOURCES

Primary articles were identified through a MEDLINE search (1966-July 2000). Key word searches included beta-blockers, Graves disease, inorganic iodide, lithium, methimazole, and propylthiouracil. Additional articles from these sources and endocrinology textbooks were also identified. We agreed to include articles that would highlight the most relevant points, as well as current areas of controversy.

DATA SYNTHESIS

Graves disease is the most common cause of hyperthyroidism. The 3 main treatment options for patients with Graves hyperthyroidism include antithyroid drugs, radioactive iodine, and surgery. Although the antithyroid drugs propylthiouracil (PTU) and methimazole (MMI) have similar efficacy, there are situations when 1 agent is preferred. MMI has a longer half-life than PTU, allowing once-daily dosing that can improve patient adherence to treatment. PTU has historically been the drug of choice for treating pregnant and breast-feeding women because of its limited transfer into the placenta and breast milk. Adjuvant therapies for Graves disease include beta-blockers, inorganic iodide, and lithium. beta-Blockers are used to decrease the symptoms of hyperthyroidism. Inorganic iodide is primarily used to prepare patients for thyroid surgery because of its ability to decrease the vascularity of the thyroid gland. Lithium, which acts in a manner similar to iodine, is not routinely used due to its transient effect and the risk of potentially serious adverse effects. In the US, radioiodine therapy has become the preferred treatment for adults with Graves disease. It is easy to administer, safe, effective, and more affordable than long-term treatment with antithyroid drugs. Hypothyroidism is an inevitable consequence of radioiodine therapy. Radioiodine is contraindicated in pregnant women because it can damage the fetal thyroid gland, resulting in fetal hypothyroidism. Bilateral subtotal thyroidectomy, which was once the only treatment available, is now performed only in special circumstances. In addition to the normal risks associated with surgery, laryngeal nerve damage, hypoparathyroidism, and hypothyroidism can occur following that procedure.

CONCLUSIONS

Despite extensive experience with medical management, controversy prevails regarding choosing among the various drugs for treatment of Graves disease. None of the treatment options, including antithyroid drugs, radioiodine, and surgery, is ideal. Each has risks and benefits, and selection should be tailored to the individual patient.

Hyperthyroidism: a "curable" cause of congestive heart failure--three case reports and a review of the literature

With the increasing incidence of coronary artery disease and the aging population, the prevalence of congestive heart failure (CHF) is increasing. In the majority of these cases the etiology is underlying coronary artery disease. Other less common causes of CHF include valvular heart disease, hypertension, alcoholic cardiomyopathy, and dilated cardiomyopathy. In addition, there are rare causes, one of which is hyperthyroidism. Hyperthyroidism can affect the cardiovascular system in a variety of ways. The cardiovascular manifestations range from sinus tachycardia to atrial fibrillation and from a high cardiac output state to CHF due to systolic left ventricular dysfunction. If the underlying hyperthyroidism is recognized and treated early the CHF in such cases can be cured. The authors present three cases of CHF due to systolic left ventricular dysfunction secondary to hyperthyroidism, which showed considerable improvement in the left ventricular function once the hyperthyroidism was treated.

Lipid abnormalities in elderly patients with subclinical hyperthyroidism

Introduction Sensitive thyroid-stimulating hormone (TSH) assays provide identification of many patients with subclinical hyperthyroidism resulting from excessive production or excessive replacement of thyroid hormone. Subclinical hyperthyroidism is defined by a TSH below normal (suppressed) with normal serum T3 and T4 levels. Subclinical hyperthyroidism is the goal of thyroid hormone therapy in patients with thyroid cancer, solitary thyroid nodules, multinodular or diffuse goiters, or a history of head and neck irradiation. Benefits of TSH suppression in these patients, were thought to exceed the risks of subclinical hyperthyroidism. Subclinical hyperthyroidism also occurs in patients with thyroiditis and those with autoimmune thyroid disease. Other causes of TSH suppression, such as use of glucocorticoids, severe illness and pituitary dysfunction should be excluded. Material and methods This investigation included 55 elderly patients with subclical hyperthyroidism in order to establish the type and degree of lipid abnormalities and effects of therapy with antithyroid drugs (methimazole 10 mg/day) during three months. These patients presented with no or minimal symptoms of thyroid hormone excess, but 56% of patients experienced atrial fibrillation and cardiac hypertrophy. Results Levels of serum cholesterol, LDL-cholesterol and HDL-cholesterol were decreased. We found a significant increase of serum cholesterol, LDL-cholesterol and HDL-cholesterol levels after treatment. Discussion and Conclusion Subclinical hyperthyroidism in elderly individuals is difficult to diagnose because it may present only with cardiac manifestations including atrial fibrillation and cardiac hypertrophy. There is general agreement that measurement of serum TSH is the most sensitive indicator of thyroid hormone activity in its target tissues. Patients with subclinical hyperthyroidism tend to have low serum total cholesterol, LDL-cholesterol anf HDL-cholesterol levels. These values increase after treatment. Most patients with subclinical hyperthyroidism should be treated with antithyroid drugs to prevent cardiovascular complications and bone loss, particulary among postmenopausal women.

Perioperative evaluation and management of the patient with endocrine dysfunction

Whenever possible, endocrine disorders should be identified and evaluated prior to surgery. A plan for perioperative management of diabetes should be based on the type of diabetes, what diabetes medications are taken, the status of diabetes control, and what type of surgery is planned. Perioperative management of diabetes must include bedside glucose monitoring. Patients with mild hypothyroidism can safely proceed with elective surgery. Elective surgery should be postponed for patients with moderate or severe hypothyroidism. Patients who have mild hyperthyroidism can undergo elective surgery with preoperative beta blockade. Elective surgery should not be done on patients with moderate or severe hyperthyroidism until they are euthyroid. Patients with pheochromocytoma need to be identified and properly treated before surgery to prevent perioperative cardiovascular complications. Patients who take endogenous steroids should have the status of their HPA axis determined prior to surgery. If the patient is undergoing moderate or major surgical stress and has documented or presumed HPA suppression, then stress doses of steroids should be give perioperatively.

Oxygen consumption in patients with hyperthyroidism before and after treatment with beta-blockade versus thyrostatic treatment: a prospective randomized study

OBJECTIVE

To evaluate randomly the effect of thyrostatic treatment (tiamazole) versus selective (metoprolol) and nonselective beta-blockade (propranolol) on whole-body energy metabolism in women with hyperthyroidism.

SUMMARY BACKGROUND DATA

beta-blockade is used as an alternative to thyrostatic drugs in the preoperative treatment of patients with hyperthyroidism. beta-blockers have well-established symptomatic effects, but in contrast to antithyroid drugs beta-blockade is thought to lack direct effects on the increased metabolism in hyperthyroidism.

METHODS

Whole-body oxygen consumption and carbon dioxide production was measured in a semiopen canopy system with paramagnetic O2 and infrared CO2 sensors. A constant flow generator and the gas-dilution method for calculation of gas flow were used. Anabolic parameters were body weight, triceps skinfold, and arm muscle circumference.

RESULTS

Tiamazole normalized oxygen consumption and induced signs of anabolism with improved nutritional state. Metroprolol did not affect oxygen consumption. Propranolol reduced elevated oxygen consumption by 54%. Body weight and other anthropometric assessments were stable after specific and nonspecific beta-blockade, which also led to symptomatic relief in approximately 90% of the patients.

CONCLUSION

Tiamazole was the most effective drug to oppose the adverse effects of hyperthyroidism. Therefore, thyrostatic agents are recommended for preoperative treatments of patients with severe catabolic hyperthyroidism. Whenever beta-blockers are chosen for treatment of hyperthyroidism, propranolol (beta 1 + beta 2) has an advantage because it reduces the metabolic rate, whereas selective beta 1-blockade seemed to provide only symptomatic relief, related to the normalization of heart rate.

Trauma and thyroid-induced tachycardia

Excluding a source of hemorrhage after blunt trauma in a patient who presents with a sustained tachycardia can be challenging. This report is of two trauma patients presenting with undiagnosed thyrotoxicosis. Trauma-triggered thyrotoxicosis is rarely reported in the literature. The confusing presentation, the laboratory analysis, and the response to therapeutic intervention are reviewed.

Stress echocardiography in hyperthyroidism

Exertion symptoms occur frequently in subjects with hyperthyroidism. Using stress echocardiography, exercise capacity and global left ventricular function can be assessed noninvasively. To evaluate stress-induced changes in cardiovascular function, 42 patients with untreated thyrotoxicosis were examined using exercise echocardiography. Studies were performed during hyperthyroidism, after treatment with propranolol, and after restoration of euthyroidism. Twenty-two healthy subjects served as controls. Ergometry was performed with patients in a semisupine position using a continuous ramp protocol starting at 20 watts/min. In contrast to control and euthyroidism, the change in end-systolic volume index from rest to maximal exercise was lower in hyperthyroidism. At rest, the stroke volume index, ejection fraction, and cardiac index were significantly increased in hyperthyroidism, but exhibited a blunted response to exercise, which normalized after restoration of euthyroidism. Propranolol treatment also led to a significant increase of delta (delta) stroke volume index. Maximal work load and delta heart rate were markedly lower in hyper- vs. euthyroidism. Compared to the control value, systemic vascular resistance was lowered by 36% in hyperthyroidism at rest, but no further decline was noted at maximal exercise. The delta stroke volume index, delta ejection fraction, delta heart rate, and maximal work load were significantly reduced in severe hyperthyroidism. Negative correlations between free T3 and diastolic blood pressure, maximal work load, delta heart rate, and delta ejection fraction were noted. Thus, in hyperthyroidism, stress echocardiography revealed impaired chronotropic, contractile, and vasodilatatory cardiovascular reserves, which were reversible when euthyroidism was restored.