Recognition and management of cardiovascular disease related to thyroid dysfunction

Acute Pericarditis Triggered by Severe Thyrotoxicosis

Acute pericarditis is a common inflammatory disorder with several causes including infection, malignancy, acute myocardial infarction, and autoimmune disease. Acute pericarditis can rarely present in the setting of thyrotoxicosis. A 65-year-old man with a past medical history of HIV, diastolic dysfunction, and prediabetes presented with positional chest pain, respiratory distress, and altered mentation. He was found down on the ground in a lethargic state and was last seen normally five days before the presentation. On presentation, he was tachycardic and tachypneic, requiring supplemental oxygenation with a nonrebreather mask to maintain adequate oxygen saturation. Initial electrocardiogram (EKG) demonstrated diffuse ST-elevations with early repolarization, consistent with acute pericarditis. Laboratory diagnostics revealed elevated lactic acid, leukocytosis, acute kidney injury, undetectable thyroid stimulating hormone, and elevations in T3, T4, C-reactive protein, brain natriuretic peptide, and creatinine kinase. Given the patient's complex presentation involving thyrotoxicosis and pericarditis, a multidisciplinary team discussion was pursued involving critical care, cardiology, and endocrinology. He was started on intravenous methylprednisolone (subsequently transitioned to prednisone), methimazole, and metoprolol. Colchicine was subsequently added for the management of pericarditis and prednisone was continued (given concomitant thyroid disease) with a plan for tapering them off, per cardiology and endocrinology recommendations. A transthoracic echocardiogram revealed a small pericardial effusion. Anticoagulation was not initiated given the potential risk of developing a hemorrhagic pericardial effusion. Thyroid ultrasound was nonsuggestive of Graves' disease. Thyrotoxicosis may present with a constellation of symptoms, including acute pericarditis. Timely recognition with EKG and echocardiography can aid in prompt management.

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.

Interplay between cardiovascular and thyroid dysfunctions: A review of clinical implications and management strategies

Cardiovascular diseases (CVD) and thyroid dysfunction are two of the most prevailing disorders in the world that are closely interlinked. Actions of thyroid hormones are mediated via thyroid receptors present in the myocardium and the vascular tissue. Primary mechanism that links thyroid dysfunction with CVD is the modification of cardiovascular risk factors (dyslipidemia, blood pressure, coagulation parameters, etc.) resulting in endothelial and left ventricular systolic and diastolic dysfunction.

Both overt and subclinical hyperthyroidism and hypothyroidism may cause adverse alterations in cardiac function. Hyperthyroidism gives rise to palpitation, atrial fibrillation, systolic hypertension, and heart failure, whereas hypothyroidism increases diastolic hypertension, pericardial effusion, and the risk of ischemic heart disease via altering lipid and coagulation parameters. Early recognition and treatment of thyroid dysfunction may prevent adverse cardiovascular events in patients with or without pre-existing CVD.

Certain cardiac conditions and medications can cause alterations in thyroid function that may predispose an individual to higher morbidity and mortality. In certain situations, thyroid dysfunction treatment may have cardiovascular benefits. This study deals with the interplay between cardiovascular and thyroid dysfunctions associated with clinical implications and management strategies.

Sudden extensive bloody pleural and pericardial effusion in a subject with untreated known hypothyroidism after total thyroidectomy, triggered by pneumonia

BACKGROUND

In subjects with hypothyroidism, edema is often observed, and pleural effusion and pericardial fluid could be also observed. The color of such fluid retention is usually yellow. Here we show a very rare case with hypothyroidism who had bloody pleural effusion and bloody pericardial fluid.

CASE PRESENTATION

A 42-year-old male noticed chest pain and the aggravation of exertional dyspnea, and he was transported to our institution by emergency. He had Graves' disease and underwent total thyroidectomy about 4 years before. After then, he had been treated with 200 μg/day of levothyroxine sodium for the maintenance of thyroid function. However, he self-interrupted such medication about 2 years before. Thyroid function on admission was reduced as follows: free triiodothyronine, 1.60 pg/mL; free thyroxine < 0.40 ng/dL; thyroid-stimulating hormone 25.50 μU/mL. Inflammation markers were increased: white blood cells 25,280 /μL; C-reactive protein 18.66 mg/dL. A large amount of pericardial fluid and pleural effusion were observed in chest and abdominal computer tomography and echocardiography. In addition, we performed pleural effusion and pericardial fluid collection. Pleural effusion in this subject showed bloody color, but not yellow. In cell block specimen of pleural effusion and pericardial fluid, red blood cells, neutrophils and lymphocyte component were observed. In this subject, however, we were unable to find any obvious background disease causing bloody pericardial effusion. Finally, we concluded that bloody pleural effusion and bloody pericardial fluid were brought about in a subject with untreated known hypothyroidism after total thyroidectomy, triggered by pneumonia.

CONCLUSIONS

In subjects with hypothyroidism, fluid and mucopolysaccharide are stored in interstitial space and protein osmolality is increased, thus leading to edema and fluid retention. It is noted here that pleural effusion and pericardial fluid in this subject showed bloody color and included red blood cells. There are no reports of bloody pericardial fluid with hypothyroidism. Therefore, it is important to keep in mind that a subject with some trigger, such as infection, may have a hematologic fluid retention that is not seen when hypothyroidism is present alone, as observed in this subject.

Protective Effects of Thyroid Hormone Deprivation on Progression of Maladaptive Cardiac Hypertrophy and Heart Failure

Purpose: Thyroid hormones (TH) play a central role for cardiac function. TH influence heart rate and cardiac contractility, and altered thyroid function is associated with increased cardiovascular morbidity and mortality. The precise role of TH in onset and progression of heart failure still requires clarification. Methods: Chronic left ventricular pressure overload was induced in mouse hearts by transverse aortic constriction (TAC). One week after TAC, alteration of TH status was induced and the impact on cardiac disease progression was studied longitudinally over 4 weeks in mice with hypo- or hyperthyroidism and was compared to euthyroid TAC controls. Serial assessment was performed for heart function (2D M-mode echocardiography), heart morphology (weight, fibrosis, and cardiomyocyte cross-sectional area), and molecular changes in heart tissues (TH target gene expression, apoptosis, and mTOR activation) at 2 and 4 weeks. Results: In diseased heart, subsequent TH restriction stopped progression of maladaptive cardiac hypertrophy and improved cardiac function. In contrast and compared to euthyroid TAC controls, increased TH availability after TAC propelled maladaptive cardiac growth and development of heart failure. This was accompanied by a rise in cardiomyocyte apoptosis and mTOR pathway activation. Conclusion: This study shows, for the first time, a protective effect of TH deprivation against progression of pathological cardiac hypertrophy and development of congestive heart failure in mice with left ventricular pressure overload. Whether this also applies to the human situation needs to be determined in clinical studies and would infer a critical re-thinking of management of TH status in patients with hypertensive heart disease.

Thyroid hormones modulate uric acid metabolism in patients with recent onset subclinical hypothyroidism by improving insulin sensitivity

Some evidence suggests a relationship between thyroid dysfunction and uric acid (UA) metabolism, but the potential influential role of thyroid hormones on UA metabolism is still debated. This report was designed to evaluate the influential role of levothyroxine (L-T4) replacement therapy on circulating levels of UA in patients with recent onset post-thyroidectomy subclinical hypothyroidism. Circulating levels of thyroid hormones, UA and other metabolic parameters were assessed in 155 recently thyroidectomized patients (131 females, mean age 51.1 ± 12.7 years) at baseline (5-7 day after surgery) and after 2 months under replacement therapy with L-T4. At baseline, circulating levels of thyroid hormones were indicative of a subclinical hypothyroidism (TSH 8.2 ± 5.1 mU/mL, FT3 2.1 ± 0.7 pg/mL, FT4 9.2 ± 3.4 pg/mL). The mean serum UA concentration was 5.0 ± 1.3 mg/dL, while the prevalence of hyperuricemia, defined by serum UA levels > 6 mg/dL, was 22.6%. Serum UA levels at baseline were significantly correlated with HOMA-IR index (r = 0.475, p < 0.0001). After 2 months under the replacement therapy with L-T4, both serum UA levels (- 1.2 ± 0.9 mg/dL, p < 0.0001 vs. baseline) and HOMA-IR (- 0.3 ± 1.5 mmol/L, p = 0.0328 vs. baseline) significantly decreased. Multivariate regression analysis revealed that changes in HOMA-IR explained 23% of the variations of serum UA levels under L-T4 replacement therapy (β = 0.295, p < 0.0001, R² = 0.230). Our study suggests that thyroid hormones could modulate UA metabolism in patients with recent onset subclinical hypothyroidism likely by improving insulin sensitivity.

Thrombin-activatable fibrinolysis inhibitor in hypothyroidism and hyperthyroxinaemia

Endocrine disorders affect both the coagulation and fibrinolytic systems, and have been associated with the development of cardiovascular diseases. Thrombin-activatable fibrinolysis inhibitor (TAFI) is a link between coagulation and the fibrinolytic system. The aim of this study was to determine the effect of thyroid hormone excess and deficiency on TAFI levels and function. The effect of hyperthyroxinemia on TAFI was studied in healthy volunteers who were randomised to receive levothyroxine or no medication for 14 days in a crossover design. The effect of hypothyroidism on TAFI was studied in a multicentre observational cohort study. Blood was drawn before treatment of patients with newly diagnosed hypothyroidism and when euthyroidism was achieved. Plasma clot-lysis times, activated TAFI (TAFIa)-dependent prolongation of clot-lysis and TAFI levels were measured. Thyroid hormone excess resulted in a hypofibrinolytic condition and in an enhanced TAFIa-dependent prolongation of clot lysis. A trend towards decreased plasma TAFI levels was observed in healthy volunteers who used levothyroxine. Hypothyroidism resulted in hyperfibrinolysis and a reduced TAFIa-dependent prolongation of clot lysis. In conclusion, alterations of TAFIa-dependent prolongation of clot lysis in patients with thyroid disorders may cause an impaired haemostatic balance. The disturbed haemostatic balance in patients with hyperthyroidism might make them prone to thrombosis, while the risk for bleeding may increase in patients with hypothyroidism.

Cardiogenic Pulmonary Edema in a Dog Following Initiation of Therapy for Concurrent Hypoadrenocorticism and Hypothyroidism

A 5 yr old intact female cocker spaniel dog weighing 7.8 kg was referred with anorexia, vomiting, and depression. At referral, the dog was diagnosed initially with typical hypoadrenocorticism, and 2 d later, concurrent primary hypothyroidism was detected. Hormonal replacement therapies, including fludrocortisone, prednisolone, and levothyroxine, were initiated, but a few days later the dog became abruptly tachypneic, and thoracic radiographs indicated the development of pulmonary edema. Echocardiography showed that there were abnormalities indicating impaired left ventricular function, although the heart valves were normal. Following treatment with pimobendan and furosemide, the pulmonary edema resolved. The dog had no recurrence of the clinical signs after 10 mo of follow-up, despite being off all cardiac medications; consequently, the cardiac failure was transient or reversible in this dog. The case report describes the stepwise diagnosis and successful treatment of cardiogenic pulmonary edema after initiation of hormonal replacement therapy for concurrent hypoadrenocorticism and hypothyroidism in a dog.

The role of hypothyroidism in the etiology and progression of dilated cardiomyopathy in Doberman Pinschers

BACKGROUND

Hypothyroidism and dilated cardiomyopathy (DCM) are both common diseases in Doberman Pinschers. A possible influence of hypothyroidism on the etiology and progression of DCM is controversial.

OBJECTIVES

Evaluation of the role of hypothyroidism in etiology and progression of DCM.

ANIMALS

A total of 175 Doberman Pinschers.

METHODS

In this longitudinal prospective study, echocardiography and 24-hour ambulatory ECG recordings were performed in all dogs as screening tests for DCM. Total thyroxine (TT4 ) and thyroid ultrasonography served as initial screening tests for hypothyroidism and low TT4 values were followed up by a thyroid stimulating hormone (TSH) test or free total thyroxine (fT4 )/cTSH measurements. Additionally, a follow-up study of dogs affected by both DCM and hypothyroidism under optimal treatment for hypothyroidism was conducted.

RESULTS

A total of 107 dogs were healthy, 45 dogs had DCM, 11 hypothyroidism, and 12 dogs had both DCM and hypothyroidism. TT4 values as well as the thyroid volumes were equivalent in the healthy dogs and in those with DCM. Neither ventricular premature complexes nor echocardiographic parameters differed between healthy and hypothyroid dogs. Dogs with DCM had a 2.26-fold (CI0.95 = 1.1-4.8) higher risk of also being affected by hypothyroidism. Despite optimal thyroid treatment of dogs with hypothyroidism and DCM, there was a progression of the heart disease.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study did not confirm a role of hypothyroidism in the etiology or progression of DCM. Treatment of hypothyroidism did not improve the clinical outcome.

Thyroid and the heart

Thyroid hormones modulate every component of the cardiovascular system necessary for normal cardiovascular development and function. When cardiovascular disease is present, thyroid function tests are characteristically indicated to determine if overt thyroid disorders or even subclinical dysfunction exists. As hypothyroidism, hypertension, and cardiovascular disease all increase with advancing age, monitoring of thyroid-stimulating hormone, the most sensitive test for hypothyroidism, is important in this expanding segment of our population. A better understanding of the impact of thyroid hormonal status on cardiovascular physiology will enable health care providers to make decisions about thyroid hormone evaluation and therapy in concert with evaluating and treating hypertension and cardiovascular disease. The goal of this review is to access contemporary understanding of the effects of thyroid hormones on normal cardiovascular function and the potential role of overt and subclinical hypothyroidism and hyperthyroidism in a variety of cardiovascular diseases.

Thyroid hormone levels within reference range are associated with heart rate, cardiac structure, and function in middle-aged men and women

BACKGROUND

Triiodothyronine (T3) has many effects on the heart, and marked changes in cardiac function and structure occur in patients with (subclinical) thyroid disease. We investigated whether between-subject variation in thyroid hormone levels within the euthyroid range is also associated with heart rate and echocardiographic heart function and structure.

METHODS

Subjects were selected from the Asklepios study (n=2524), a population-representative random sample of patients aged between 35 and 55 years, free from overt cardiovascular disease at baseline. Analyses were restricted to 2078 subjects (1013 women and 1065 men), not using antihypertensive or thyroid medication nor having antithyroperoxidase antibody levels above clinical cut-off or thyrotropin (TSH) levels outside the reference range. All subjects were phenotyped in-depth and underwent comprehensive echocardiography, including diastolic evaluation. Thyroid function parameters were determined by automated electrochemiluminescence.

RESULTS

Heart rate was robustly positively associated with (quartiles of) free T3 (FT3) and T3, both in subjects with TSH levels within reference (0.27-4.2 μU/L) and in narrow TSH range (0.5-2.5 μU/L; p<0.0001). FT3 and T3 were negatively associated with left ventricular (LV) end-diastolic volume but positively associated with relative wall thickness. Total T3 (TT3) was associated with enhanced ventricular contraction (as assessed by tissue Doppler imaging). Free thyroxine, FT3, and TT3 were positively associated with late ventricular filling, and TT3 was associated with early ventricular filling.

CONCLUSION

We have demonstrated a strong positive association between thyroid hormone levels within the euthyroid range and heart rate, and more subtle effects on cardiac function and structure. More specifically, we suggest a smaller LV cavity size (with increased relative wall thickness), an enhanced atrial and ventricular contraction, and LV relaxation with higher circulating thyroid hormones. These results illustrate that variation in thyroid hormone levels, even within the reference range, exerts effects on the heart.

Lean body mass-based levothyroxine replacement in young athyrotic patients with differentiated carcinoma of thyroid

OBJECTIVE

The objective of this study was to optimize dose of levothyroxine (LT4) based on lean body mass (LBM) in young athyrotic patients with differentiated carcinoma of thyroid (DCT) which has not been properly addressed in Bangladesh before.

MATERIALS AND METHODS

SIXTY PATIENTS WITH DCT (AGE, RANGE: 20-39 years) having total thyroidectomy followed by radioiodine ablative therapy (RIT) and 23 euthyroid volunteers were recruited. Clinical, biochemical parameters were obtained from all patients after 2 months of RIT and on LT4 replacement at a dose of 200 μg/day as first follow up visit and also from control subjects. Then 60 patients were divided into two groups consisting of 30 patients each. Patients of Group-I received LT4 replacement based on LBM measured by dual energy X-ray absorptiometry (DXA) and Group-II continued LT4 replacement in conventional dose. Patients of both groups were assessed again for same parameters at 6 to 12 months at the second visit.

RESULTS

Optimized dose of LT4 based on LBM by DXA (131 ±23 μg/day) significantly reduced thyroid hormones and kept thyroid stimulating hormone (TSH) in expected levels in patients of Group-I at the second visit compared to patients of Group-II who continued conventional LT4 dose (200 μg/day). Hyperthyroid symptom scale (HSS) was significantly reduced to 2 ± 1 in patients of Group-I but not in patients of Group-II, HSS, 8 ±1 (P > 0.001).

CONCLUSION

Optimization of LT4 dose based on LBM can avoid chronic exposure of mild excess of thyroid hormone in young patients with low risk DCT.

Thyroid hormone receptor-α and vascular function

Thyroid hormone (TH) treatment exerts beneficial effects on the cardiovascular system: it lowers cholesterol and LDL levels and enhances cardiac contractile function. However, little is known about the effect of TH on vascular function or the functional role of TH receptors (TRs) in the regulation of vascular tone. We have investigated the contribution of TRs to vascular contractility in the heart. Among different TR subtype-specific knockout (KO) mice, vascular contraction was significantly enhanced in coronary arteries isolated from TRα KO compared with wild-type mice, while chronic TH treatment significantly attenuated coronary vascular contraction. We found that TRα is the predominant TR in mouse coronary smooth muscle cells (SMCs). Coronary SMCs isolated from TRα KO mice exhibited a significant decrease in K(+) channel activity, whereas TH treatment increased K(+) channel activity in a dose-dependent manner. These data suggest that TRα in SMCs has prominent effects on regulation of vascular tone and TH treatment helps decrease coronary vascular tone by increasing K(+) channel activity through TRα in SMCs.

Hypothyroidism in a five-year-old boy with rhabdomyolysis and recent history of cardiac tamponade: a case report

INTRODUCTION

Cardiac tamponade is a rare manifestation of hypothyroidism, and a less rare cause of pericardial effusion. The accumulation of the pericardial fluid is gradual, and often does not compromise cardiac hemodynamic function. There is a relationship between the severity and chronicity of the disease with the presence of pericardial effusion. There are few cases describing associated pericardial tamponade published in the literature. When a tamponade occurs, a concomitant provocative factor such as a viral pericarditis may be related. Our patient's case appears to be the youngest patient described so far.

CASE PRESENTATION

We report the case of a previously healthy five-year-old Hispanic (non-indigenous) boy who developed rhabdomyolysis with a history of a recent pericardial effusion and tamponade two months before that required the placement of a percutaneous pericardial drainage. Pericardial effusion was considered to be viral. Later on readmission, clinical primary hypothyroidism was diagnosed and thought to be associated with the previous cardiac tamponade. He developed rhabdomyolysis, which was considered to be autoimmune and was treated with steroids. The level of creatine phosphate kinase and creatine kinase MB fraction returned to within the reference rangeone week after our patient was started on steroids and three weeks after he was started on thyroid hormones.

CONCLUSIONS

Physicians should consider hypothyroidism as a differential diagnosis in patients with pericardial effusion. Pericardial effusion may progress and cause a cardiac tamponade with hemodynamic instability. The fact that our patient did not have any manifestations of hypothyroidism might have delayed diagnosis.

Hypothyroidism and moderate subclinical hypothyroidism are associated with increased all-cause mortality independent of coronary heart disease risk factors: a PreCIS database study

BACKGROUND

Thyroid hormones have profound effect on the heart and peripheral vasculature. Hypothyroidism is associated with an increase in a number of coronary heart disease (CHD) risk factors including dyslipidemia, hypertension, and elevated levels of homocysteine. Our objective was to assess the effects of hypothyroidism (thyroid-stimulating hormone [TSH]: >10 μ U/mL), moderate subclinical hypothyroidism (SCH; TSH: 6.1-10 μ U/mL), and mild SCH (TSH: 3.1-6.0 μ U/mL) on cardiovascular risk factors, CHD prevalence, and all-cause mortality in patients at high risk for CHD seen in a preventive cardiology clinic.

METHODS

All patients seen in the Cleveland Clinic Preventive Cardiology clinic have demographic and laboratory tests including TSH and multiple CHD risk factors obtained at the baseline visit. All data are entered into a database (called PreCIS). The social security death index is queried monthly to determine all-cause mortality.

RESULTS

Several CHD risk factors including age, male gender, systolic blood pressure, triglycerides, and fibrinogen were more common in hypothyroid patients. Prevalence of CHD was more common in hypothyroid and moderate SCH patients. All-cause mortality was higher in hypothyroid and moderate SCH patients, but not in mild SCH patients. Higher mortality in these groups was observed in both genders, patients under 65 years of age, and patients not on thyroid replacement therapy, but was not observed in patients over 65 years of age.

CONCLUSIONS

Hypothyroidism and moderate, but not mild, SCH are associated with increased CHD prevalence and all-cause mortality. These observations suggest patients with moderate, but not mild, SCH and patients at high risk for CHD should be treated with thyroid replacement therapy.

Sunitinib-induced severe hypothyroidism with cardiac compromise

Tyrosine kinase inhibitors (TKI) are an increasingly used class of anti-cancer agent. Sunitinib (sutent(®), Pfizer™, New York) is standard first-line therapy for patients with metastatic renal cancer. It is associated with a number of toxicities, including thyroid dysfunction. We present a case of sunitinib-induced severe hypothyroidism resulting in cardiac compromise. The case highlights the importance of interval thyroid function monitoring for patients on drugs, such as sunitinib and other TKIs.

Sheehan syndrome with reversible dilated cardiomyopathy

Cardiac abnormalities in patients with Sheehan syndrome are uncommon. A case of Sheehan syndrome with dilated cardiomyopathy is presented in whom hormone replacement with levothyroxine and prednisolone resulted in complete recovery of cardiomyopathy. A 25-year-old woman presented with lactation failure, secondary amenorrhea, features of hypothyroidism and a hypocortisol state following severe postpartum hemorrhage after her last child birth. She also had smear positive pulmonary tuberculosis. After starting antitubercular treatment, she developed shock, suggestive of hypocortisol crisis. Hormonal investigations revealed evidence of panhypopitutarism and magnetic resonance imaging revealed partial empty sella. Meanwhile echocardiography revealed evidence of dilated cardiomyopathy (DCM). The patient was given replacement therapy in the form of glucocorticoids and levothyroxine in addition to antitubercular treatment. She improved and on follow-up over a period of 7 months, the DCM completely reversed. To our knowledge this is the first report of reversible DCM in a patient with Sheehan syndrome.

Thrombin-Activatable Fibrinolysis Inhibitor (TAFI) Antigen and Activity Assay in Patients With Primary Hypothyroidism

Hypothyroidism causes a tendency for cardiovascular diseases. It was recently shown that thrombin-activatable fibrinolysis inhibitor (TAFI) attenuates fibrinolysis and also fibrin-plasminogen interaction by the removal of lysine and arginine residues from fibrin monomers. The aim of this study was to determine the effects of overt hypothyroidism on the levels of TAFI antigen (TAFI Ag) and TAFI activity (TAFIa). Thirty-one overt primary hypothyroid patients and age- and gender-matched 25 healthy controls were enrolled in the study. Patients were treated with L-thyroxine after the collection of blood samples. Thyroid functions were reevaluated following the achievement of euthyroid status. Thrombin-activatable fibrinolysis inhibitor Ag, tissue plasminogen activator (t-PA), and plasminogen activator inhibitor 1 (PAI-1) levels were measured with the enzyme-linked immunosorbent assay (ELISA). Thrombin-activatable fibrinolysis inhibitor activity was assessed with the chromogenic assay. Thrombin-activatable fibrinolysis inhibitor Ag (1.63% ± 0.42% vs 1.32% ± 0.36%, P < .01) and TAFIa (14.2 ± 4.12 vs 11.6 ± 3.49 μg/mL, P < .05) levels were elevated in hypothyroid patient compared to controls. Plasminogen activator inhibitor 1 and t-PA levels were not significantly different between both groups. In hypothyroid patients, TAFI Ag levels were correlated with free T4 (r = -.373, P < .05) and thyroid-stimulating hormone (TSH) levels (r = .748, P < .001). Regression analysis showed that TSH levels were predictors of TAFI Ag levels (P < .001, β =.671, 95% confidence interval [CI]: 0.008-0.017). Following L-thyroxine treatment, TAFI Ag (1.63% ± 0.42%, 1.34% ± 0.33%, P < .05) and TAFIa (14.2 ± 4.12 μg/mL, 12.0 ± 2.77 μg/mL, P < .05) levels were significantly decreased, but t-PA and PAI-1 levels remained unchanged. This results point out that the fibrinolytic activity was decreased in hypothyroid patients, and therefore the achievement of euthyroid status is important in ameliorating the increased risk of cardiovascular disease.

Changes in body composition in women following treatment of overt and subclinical hyperthyroidism

OBJECTIVE

To determine changes in weight, body composition, and bone density after treatment of overt hyperthyroidism (OH) and subclinical hyperthyroidism (SCH) in women.

METHODS

Women with OH and SCH referred to the Mayo Clinic Thyroid Clinic were recruited. Hyperthyroid patients and euthyroid control women were matched for age (within decade) and body mass index. Patients with OH and SCH were treated to normalize thyroid function test results and were restudied after 6 months of normal thyroid function. Baseline and posttreatment studies included measurement of height, weight, bone density, lean mass, fat mass, and thigh muscle cross-sectional area. All participants had normal thyroid function test results for at least 6 months before completion of the posttreatment studies.

RESULTS

Twenty-four patients with OH, 21 patients with SCH, and 36 control patients were studied. In the OH group, fat-free mass increased from a mean of 36.8 kg (95% confidence interval [CI], 34.8-38.8) to 40.4 kg (95% CI, 38.5-42.3); in the SCH group, fat-free mass increased from a mean of 40.3 kg (95% CI, 38.1-42.5) to 42.2 kg (95% CI, 39.7-44.7). In both groups, fat mass increased to approximately the same extent, and both groups experienced significant weight gain with no change in percent body fat. Thigh muscle cross-sectional area increased in both groups -- from 100.6 cm(2) (95% CI, 92.7-108.5) to 113.3 cm(2) (95% CI, 105.5-121.1) in the OH group and from 106.1 cm(2) (95% CI, 96.7-115.5) to 112.2 cm(2) (95% CI, 102.0-122.4) in the SCH group. Bone density increased in patients with OH (P<.01) and in patients with SCH (P<.05).

CONCLUSIONS

Treatment of OH and SCH leads to increases in muscle area and bone density. Weight gain reflects increases in both fat and fat-free mass. While these results provide some support for actively treating SCH in women, further prospective studies are needed to determine whether the changes documented translate into real patient benefit.

Thyroid hormone receptor-beta is associated with coronary angiogenesis during pathological cardiac hypertrophy

Insufficient angiogenesis is one of the causes leading to tissue ischemia and dysfunction. In heart failure, there is increasing evidence showing decreased capillary density in the left ventricle (LV) myocardium, although the detailed mechanisms contributing to it are not clear. The goal of this study was to investigate the role of thyroid hormone receptors (TRs) in the coronary microvascular rarefaction under pathological cardiac hypertrophy. The LV from hypertrophied/failing hearts induced by ascending aortic constriction (AAC) exhibited severe microvascular rarefaction, and this phenomenon was restored by chronic T(3) administration. Coronary endothelial cells (ECs) isolated from AAC hearts expressed lower TRbeta mRNA than control ECs, and chronic T(3) administration restored TRbeta mRNA expression level in AAC hearts to the control level. Among different TR subtype-specific knockout mice, TRbeta knockout and TRalpha/TRbeta double-knockout mice both exhibited significantly less capillary density in LV compared with wild-type mice. In vitro, coronary ECs isolated from TRbeta knockout mice lacked the ability to form capillary networks. In addition, we identified that kinase insert domain protein receptor/fetal liver kinase-1 (vascular endothelial growth factor-2 receptor) was one of the angiogenic mediators controlled by T(3) administration in the AAC heart. These data suggest that TRbeta in the coronary ECs regulates capillary density during cardiac development, and down-regulation of TRbeta results in coronary microvascular rarefaction during pathological hypertrophy.

Thyroid stimulating hormone and left ventricular function

CONTEXT

Overt hypo- and hyperthyroidism are associated with cardiac disease, whereas this relation is more uncertain regarding subclinical thyroid dysfunction.

OBJECTIVE

The objective was to assess the relation between serum TSH level and cardiac function.

DESIGN

We conducted a cross-sectional epidemiological study and a nested case-control study.

SETTING

The study was performed at a university hospital.

SUBJECTS

A total of 2035 subjects were included in the epidemiological study and 204 subjects in the nested case-control study (serum TSH < 0.50, 0.50-3.49, and 3.50-10.0 mIU/liter in 20, 118, and 66 subjects, respectively, all with normal serum free T(4) and free T(3) levels).

MAIN OUTCOME MEASURES

Left ventricular mass by body surface area (LVMI) and indices of left ventricular function, as assessed by conventional and pulsed-wave tissue Doppler (PWTD) echocardiography, were recorded.

RESULTS

No significant relation was found between serum TSH level and LVMI. In the nested case-control study, the subjects with serum TSH 3.50-10.0 mIU/liter had no signs of cardiac dysfunction. However, the PWTD data showed higher velocities at all measurement sites in the subjects with serum TSH less than 0.50 mIU/liter as compared with the euthyroid group.

CONCLUSIONS

With the possible exception of overt hypo- and hyperthyroidism, there is no significant association between serum TSH level and LVMI. Subjects with subclinical hypothyroidism, in whom the mean serum TSH level is slightly above the reference range, appear to have normal cardiac function, whereas subjects with serum TSH levels less than 0.5 mIU/liter appear to have changes in myocardial velocities detected by PWTD.

Cardiogenic shock in hypothyroidism

A patient with minimal coronary artery disease presented in cardiogenic shock when her previously undiagnosed hypothyroid state was complicated by an episode of AV nodal re-entrant tachycardia. She did not respond to multiple pressors, and recovered dramatically after starting thyroid supplementation. Hypothyroidism caused her lack of responsiveness to pressors and perpetuated her hypotension and increased filling pressures long after she reverted to a sinus rhythm. Our case dramatically demonstrates the severe lack of physiologic reserve that can be associated with hypothyroidism.

Postprandial lipemia as a risk factor for cardiovascular disease in patients with hypothyroidism

Postprandial lipoprotein metabolism is suggested to play a role in the pathogenesis of atherosclerosis. In this study, we investigated postprandial lipemia and its relationship to cardiovascular risk factors in patients with overt and subclinical hypothyroidism. Twenty-nine female patients with TSH levels greater than 5 microIU/mL and 12 euthyroid control female subjects were included in the study. Fifteen patients had subclinical hypothyroidism and 14 had overt hypothyroidism. All subjects underwent an oral lipid tolerance test. If triglyceride levels increased by 80% or more, subjects were considered postprandial lipemia positive. Control, overt hypothyroid, and subclinical hypothyroid groups were not statistically different with respect to anthropometric measurements, fasting blood C-reactive protein, uric acid, homocysteine, glucose, insulin, lipoprotein (a), apolipoprotein B levels, and homeostasis model assessment index. Fasting triglyceride levels correlated positively with TSH levels. Postprandial lipemia frequency was higher in overt hypothyroid subjects than in the control group. The subclinical hypothyroid group did not differ from the hypothyroid group with respect to postprandial lipemia frequency. In subjects with TSH levels higher than 5 microIU/mL, PPL risk was increased sevenfold. The results of this study show that postprandial triglyceride metabolism is affected in hypothyroidism.

Which thyroid-stimulating hormone level should be sought in hypothyroid patients under L-thyroxine replacement therapy?

We sought to determine whether relationships exist between level of thyroid-stimulating hormone (TSH) suppression and cardiovascular risk parameters such as plasma homocysteine, C-reactive protein (CRP), fibrinogen, D-dimer and serum cholesterol in patients taking L-thyroxine-replacement therapy (LT4-RT). Four hundred and two hypothyroid patients under LT4-RT were cross-sectionally evaluated. Patients were grouped according to their achieved TSH (mIU/l) levels under LT4-RT on an arbitrary manner. Those patients having a TSH value 0.4-2 were defined as group 1 (n = 154), a TSH level of 2 to less than 5.5 were defined as group 2 (n = 176) and a TSH level of 5.5 to less than 20 with a normal free T3 and free T4 level were defined as group 3 (n = 72). The three groups of patients were also compared with overt hypothyroid patients (n = 71) and healthy controls (n = 97). Homocysteine levels (micromol/l) were significantly different between the three groups (10.4 +/- 4 for group 1, 11.3 +/- 3.7 for group 2 and 13.5 +/- 4.7 for group 3; p < 0.01 for all groups). Significant differences in CRP (mg /l) levels were present between the three groups (2.6 +/- 2.6 for group 1, 3.3 +/- 2.9 for group 2 and 4.8 +/- 4.1 for group 3; p < 0.01 for all groups). Univariate analysis showed that both homocysteine and CRP levels significantly correlated with free T4 and TSH level (p < 0.01 for both groups). No statistically significant differences were noticed in respect to fibrinogen and d-dimer levels between three groups. In examining the effect of LT4-RT on lipid parameters, a tendency towards beneficial effects without achieving statistical significance was observed. Practically speaking, a target TSH level of less than 2 might be advisable to lower CRP levels and homocysteine levels, and possibly lipid parameters.

Germain D, MacLennan DH, Backx PH. Cardiac-specific elevations in thyroid hormone enhance contractility and prevent pressure overload-induced cardiac dysfunction

Thyroid hormone (TH) is critical for cardiac development and heart function. In heart disease, TH metabolism is abnormal, and many biochemical and functional alterations mirror hypothyroidism. Although TH therapy has been advocated for treating heart disease, a clear benefit of TH has yet to be established, possibly because of peripheral actions of TH. To assess the potential efficacy of TH in treating heart disease, type 2 deiodinase (D2), which converts the prohormone thyroxine to active triiodothyronine (T3), was expressed transiently in mouse hearts by using the tetracycline transactivator system. Increased cardiac D2 activity led to elevated cardiac T3 levels and to enhanced myocardial contractility, accompanied by increased Ca(2+) transients and sarcoplasmic reticulum (SR) Ca(2+) uptake. These phenotypic changes were associated with up-regulation of sarco(endo)plasmic reticulum calcium ATPase (SERCA) 2a expression as well as decreased Na(+)/Ca(2+) exchanger, beta-myosin heavy chain, and sarcolipin (SLN) expression. In pressure overload, targeted increases in D2 activity could not block hypertrophy but could completely prevent impaired contractility and SR Ca(2+) cycling as well as altered expression patterns of SERCA2a, SLN, and other markers of pathological hypertrophy. Our results establish that elevated D2 activity in the heart increases T3 levels and enhances cardiac contractile function while preventing deterioration of cardiac function and altered gene expression after pressure overload.

Evaluation of Right Ventricular Function in Patients with Thyroid Dysfunction

BACKGROUND

Thyroid gland dysfunction affects the structure and function of the heart. Tissue Doppler echocardiography is a new technique, and it has been used frequently in the evaluation of ventricular function. In the present study, right ventricular function was assessed in patients with overt or subclinical hypothyroidism and hyperthyroidism and in healthy subjects using the tissue Doppler method, and results were compared.

PATIENTS AND METHODS

20 healthy subjects and 63 patients diagnosed with overt and subclinical hypothyroidism and hyperthyroidism were included in the study. Annular and myocardial systolic peak velocities, early and late diastolic peak velocities, precontraction, total contraction and relaxation times of the right ventricle were recorded by tissue Doppler echocardiography. The results of the patients were compared to those of the controls.

RESULTS

Myocardial systolic velocity was significantly higher in patients with hyperthyroidism. Annular and myocardial late diastolic velocities were found to be significantly lower in patients with overt hypothyroidism. Annular precontraction time was increased in patients with overt and subclinical hypothyroidism. Myocardial precontraction time was decreased in patients with hyperthyroidism, and increased in patients with overt hypothyroidism patients. Annular relaxation time was increased in patients with overt hypothyroidism.

CONCLUSIONS

Right ventricular function is affected in patients with thyroid diseases. The tissue Doppler technique is a suitable tool to detect impairments in right ventricular function. There is a significant correlation between serum thyroid hormone levels and right ventricular velocities and time intervals.

Tissue Doppler echocardiography in evaluation of cardiac effects of subclinical hypothyroidism

OBJECTIVE

Subclinical hypothyroidism (SH) is a mild form of thyroid failure, associated with initial signs of cardiovascular hypothyroidism. Tissue Doppler echocardiography (TDE) is a new and powerful method in evaluation of both regional and global systolic or diastolic ventricular function. We aimed to investigate the use of TDE in evaluation of cardiac effects of SH and affect of thyroid hormone replacement therapy (TRT) on tissue Doppler parameters of SH patients.

METHODS

Twenty-two patients who were diagnosed as SH and 22 healthy, age and sex-matched cases were included in the study. Conventional echocardiography and TDE were performed in all individuals. TRT was started in SH group. On the achievement of euthyroid state echocardiography were repeated.

RESULTS

Septal annulus relaxation time was significantly higher in SH group (82+/-21, 98+/-11 ms, p=0.024). Lateral annulus and myocardial relaxation times, precontraction/contraction ratios and precontraction times were also slightly higher. Septal lateral annulus and lateral myocardial relaxation times were decreased after TRT (98+/-11 vs. 81+/-12, p<0.001, 89+/-14 vs. 78+/-11, p=0.022, 90+/-16 vs. 80+/-14 ms, p=0.008, respectively). Precontraction times and precontraction/contraction ratios decreased after TRT but did not reach the significance level. There was a positive correlation between TSH and TDE relaxation times.

CONCLUSIONS

TDE is a powerful tool in diagnosis and follow-up of SH patients and TRT inhibits adverse affects of SH on myocardium. Septal myocardium is the most affected region of left ventricle in SH. The relaxation time is the best criteria of cardiac involvement and monitoring the effect of TRT.

A patient with Graves' disease accompanied by bloody pericardial effusion

A hyperthyroid patient with bloody pericardial effusion is presented. He was hospitalized for severe dyspnea. Pericardiocentesis yielded 1.2 liters of bloody fluid. Biochemical, cytologic, and radiologic examinations failed to identify the etiology of the effusion. Upon normalization of thyroid function using antithyroid drugs, the pericardial effusion resolved without recurrence. The patient was diagnosed as Graves' disease, which rarely is complicated by bloody pericardial effusion. As it is rarely reported and not widely known, this association may be underdiagnosed.

Thyroid hormone action in the heart

The heart is a major target organ for thyroid hormone action, and marked changes occur in cardiac function in patients with hypo- or hyperthyroidism. T(3)-induced changes in cardiac function can result from direct or indirect T(3) effects. Direct effects result from T(3) action in the heart itself and are mediated by nuclear or extranuclear mechanisms. Extranuclear T(3) effects, which occur independent of nuclear T(3) receptor binding and increases in protein synthesis, influence primarily the transport of amino acids, sugars, and calcium across the cell membrane. Nuclear T(3) effects are mediated by the binding of T(3) to specific nuclear receptor proteins, which results in increased transcription of T(3)-responsive cardiac genes. The T(3) receptor is a member of the ligand-activated transcription factor family and is encoded by cellular erythroblastosis A (c-erb A) genes. T(3) also leads to an increase in the speed of diastolic relaxation, which is caused by the more efficient pumping of the calcium ATPase of the sarcoplasmic reticulum. This T(3) effect results from T(3)-induced increases in the level of the mRNA coding for the sarcoplasmic reticulum calcium ATPase protein, leading to an increased number of calcium ATPase pump units in the sarcoplasmic reticulum.

The evaluation of left ventricular hypertrophy in hypertensive patients with subclinical hyperthyroidism

The aim of this prospective cross-sectional study was to investigate the hypertrophic effects of endogenous subclinical hyperthyroidism on myocardium and early development of left ventricular hypertrophy (LVH) in essential hypertensive patients accompanied by endogenous subclinical hyperthyroidism. A total of 31 consecutive patients with stage I hypertension were included in the study. Sixteen of them also had endogenous subclinical hyperthyroidism that they were unaware before. The patients and the controls formed out of ten healthy subjects all underwent an investigation of thyroid functions and cardiologic evaluation. The mean wall thickness of the left ventricle in the stage I hypertensive group with endogenous subclinical hyperthyroidism (group I) was significantly increased as compared with both hypertensive patients without thyroid disease (group II) and the control subjects. The mean left ventricle mass was also significantly higher in group I than group II. Both of the patients' groups had an increased prevalence of LVH as compared with the controls. In this study, hypertensive patients with subclinical hyperthyroidism presented more increase in left ventricular mass, suggesting that subclinical hyperthyroidism may contribute to left ventricular hypertrophy forming a natural progression to hypertension. The hypertensive population should always be screened for endogenous subclinical hyperthyroidism, and should be examined for the criteria of left ventricular hypertrophy by echocardiography in early stages.

Thyroid Disorders in Elderly Patients

Thyroid disorders are common in the elderly and are associated with significant morbidity if left untreated. Typical symptoms may be absent and may be erroneously attributed to normal aging or coexisting disease. Physical examination of the thyroid gland may not be helpful, as the gland is often shrunken and difficult to palpate. Usually only myxedema coma requires levothyroxine parenterally; all other forms of hypothyroidism can be treated with oral levothyroxine. Low-dose levothyroxine should be initiated and increased gradually over several months. In unstable elderly patients with hyperthyroidism, antithyroid medication can quickly produce a euthyroid state. Radioactive iodine therapy is more definitive and is well tolerated, effective, and preferred. Surgical thyroid ablation may be necessary in patients who fail to respond to radioactive iodine therapy and in patients with multinodular goiter. If there is a suspicion of malignant disease, early biopsy or fine needle aspiration for cytology should be considered.

[Hypothyroid dilated cardiomyopathy]

Most patients with dilated cardiomyopathy have a poor prognosis due to progressive and irreversible myocardial dysfunction. Rarely, is a metabolic etiology responsive to specific therapy identified. Although many studies have confirmed that thyroid hormone deficiency is associated with a reversible decrease in myocardial contractility, it has remained controversial whether hypothyroidism alone can cause a dilated cardiomyopathy and clinical heart failure. In this study, we report the case of a patient with severe hypothyroidism and a dilated cardiomyopathy complicated by heart failure, which has receded after recovery to euthyroidism with L-thyroxin therapy. This case suggests that hypothyroidism should be evoked systematically when a dilated cardiomyopathy is diagnosed.

Effects of thyroxin therapy on cardiac function in patients with subclinical hypothyroidism: index of myocardial performance in the evaluation of left ventricular function

OBJECTIVE

We investigated the effects of thyroxine (T4) therapy on the cardiac function in subclinical hypothyroidism (SHT) by using the index of myocardial performance (IMP) and the conventional echocardiographic parameters.

METHODS

Forty-five SHT patients (F/M:38/7, age 39.9+/-7.9) and 29 healthy subjects (F/M:25/4, age 38.3+/-8.6) were studied. Patients were randomly assigned, in a double-blind manner to receive T4 therapy (group I) or a placebo (group II) and for a period of up to 12 months, were followed up using thyroid function tests and both conventional and Doppler echocardiographic measurements.

RESULTS

At the baseline, the SHT patients has a significantly higher isovolumic relaxation time (IRT) (98.3+/-23.7 vs. 81.7+/-14.7<0.01), IMP (0.52+/-0.06 vs. 0.42+/-0.05; P<0.001), A max (late mitral peak velocity) (83.4+/-12.6 vs. 74.3+/-13.5; P<0.01) and significantly lower (early mitral peak velocity) Emax/Amax ratio (1.19+/-0.18 vs. 1.34+/-0.17; P<0.01) than the individuals in the control group. In group I, the thyroid hormone profile became normalized after 1 year of L-T4 therapy, but there was no significant change in the left ventricular (LV) morphology or systolic function. After 1 year of follow-up, group I showed a significant reduction of MPI (0.53+/-0.05 vs. 0.42+/-0.07; P<0.001), Amax (84.2+/-13.7 vs. 74.5+/-11; P<0.001) and IRT (98.6+/-23.7 vs. 82.9+/- 23.3; P<0.001) along with a normalization of the E/A ratio (1.17+/-0.16 vs. 1.33+/-0.19; P<0.001). Conversely, no change was observed in group II.

CONCLUSIONS

An impairment of left ventricular diastolic function, which may be reversible with T4 therapy, was observed in the SHT patients, and IMP may be useful in the evaluation of LV myocardial dysfunction in these patients.

Hypothyroidism as a risk factor for cardiovascular disease

The cardiovascular risk in patients with hypothyroidism is related to an increased risk of functional cardiovascular abnormalities and to an increased risk of atherosclerosis. The pattern of cardiovascular abnormalities is similar in subclinical and overt hypothyroidism, suggesting that a lesser degree of thyroid hormone deficiency may also affect the cardiovascular system. Hypothyroid patients, even those with subclinical hypothyroidism, have impaired endothelial function, normal/depressed systolic function, left ventricular diastolic dysfunction at rest, and systolic and diastolic dysfunction on effort, which may result in poor physical exercise capacity. There is also a tendency to increase diastolic blood pressure as a result of increased systemic vascular resistance. All these abnormalities regress with L-T4 replacement therapy. An increased risk for atherosclerosis is supported by autopsy and epidemiological studies in patients with thyroid hormone deficiency. The "traditional" risk factors are hypertension in conjunction with an atherogenic lipid profile; the latter is more often observed in patients with TSH >10 mU/L. More recently, C-reactive protein, homocysteine, increased arterial stiffness, endothelial dysfunction, and altered coagulation parameters have been recognized as risk factors for atherosclerosis in patients with thyroid hormone deficiency. This constellation of reversible cardiovascular abnormalities in patient with TSH levels <10 mU/L indicate that the benefits of treatment of mild thyroid failure with appropriate doses of L-thyroxine outweigh the risk.

Iodine repletion, thyrotoxicosis and atrial fibrillation in Isfahan, Iran

BACKGROUND

Iodized salt was reintroduced in Iran in 1989. Just before distribution of iodized salt, thyrotoxicosis was observed in 3.7% of the patients with atrial fibrillation (AF) in university teaching hospitals in Isfahan, a centrally located city in Iran. As repletion of iodine may increase the rate of autoimmune thyroid diseases and toxic multinodular goiter, this study was designed to evaluate the rate of thyrotoxicosis in patients with AF in the same hospitals after about a decade of iodized salt consumption.

METHODS

In a case-control study with convenience sampling, 100 patients with AF and an equal number of age- and sex-matched subjects taking the same medications were selected as case and control groups, respectively, in university hospitals in 1997.

RESULTS

Eight percent of patients with atrial fibrillation had overt thyrotoxicosis versus one percent in the control group (odds ratio=8.6, 95% CI = 6.5 to 10.7, P<0.02). Thyrotoxicosis in patients with AF was 8 times higher than in the control group without AF. In comparison with the period before use of iodized salt, AF more than doubled (8% vs. 3.7%).

CONCLUSION

Thyroid function should be evaluated in all patients older than 40 years of age with AF. The benefits of iodine supplementation are great, but more attention should be paid to the complications of iodine repletion, including thyrotoxicosis and its frequent accompaniment, AF.

Effect of thyroid hormone supplementation on survival of euthyroid dogs with congestive heart failure due to systolic myocardial dysfunction: a double-blind, placebo-controlled trial

Nineteen euthyroid dogs of 12 breeds with echocardiographic signs of dilated cardiomyopathy (DCM) and radiographic and clinical signs of congestive heart failure (CHF) were evaluated in a randomised, double-blind, and placebo-controlled study. The dogs received either thyroxine or placebo as an adjunct to digoxin, furosemide and propranolol. The group assignment of individual dogs and serum concentrations of thyroid hormones remained unknown to owners and investigators during the entire study period. Dogs were evaluated clinically and with electrocardiography (ECG), thoracic radiography, echocardiography and measurement of total thyroxine (tT4) and thyroid stimulating hormone (TSH) before beginning of the trial, and then one week, 2 months, 6 months and yearly after initial examination, and, when applicable, at the time of euthanasia. End-point of the study was euthanasia (n = 17) due to severe congestive heart failure or sudden death (n = 2). Survival times ranged from 17 to 1030 days (median 187 days) in the placebo group, and from 18 to 1000 days (median 73 days) in the treatment group. There was no statistically significant difference in survival times between the treatment group and the placebo group (p = 0.46). Post mortem and histopathologic examinations revealed the attenuated wavy fiber type of DCM in 11 dogs, and myocardial infarcts, arteriosclerosis and chronic valvular disease in one dog. In conclusion, there was a wide range in survival times of dogs treated with digoxin, furosemide and propranolol. Adding thyroid hormones to the treatment did not significantly influence survival.

Cardiac changes in subclinical and overt hyperthyroid women: retrospective study

BACKGROUND

This retrospective and descriptive 4-year study was undertaken to describe cardiac changes in subclinical and overt hyperthyroidism.

METHODS

We revised the charts of 386 consecutive cardiopathic women whose blood samples were referred to the Radioimmunoassay Laboratory to evaluate thyroid function from 1 January 1997 through 31 December 2000.

RESULTS

After excluding women because euthyroid or hypothyroid, or taking amiodarone and women with hypertension, rheumatic disease, myocardial infarction, a total of 31 hyperthyroid women were thus selected for the study: 19 with subclinical hyperthyroidism and 12 with overt hyperthyroidism. The prevalence of atrial fibrillation did not differ between subclinical (48%) and overt (67%) hyperthyroid women, as well as left atrial dimension; the latter was larger in hyperthyroid (27.8+/-7.8 cm(2)/m(2)) than in control women (18.9+/-2.8 cm(2)/m(2)) (P<0.001). In the subclinical and overt hyperthyroidism, the heart rate (HR) was increased and left ventricular end diastolic (LVED) volume was reduced; in addition, only in overt hyperthyroidism, left ventricular (LV) mass was increased. A significant correlation between LV mass and free triiodothyronine was found.

CONCLUSION

HR increase and LVED decrease, both in subclinical and overt hyperthyroidism, indicate a global impairment of diastolic heart performance, complicated in overt hyperthyroidism by LV concentric hypertrophy. So, in our opinion, subclinical hyperthyroidism, far from being considered a simple laboratory finding, in clinical practice should be taken into serious consideration.

Hypothyroidism and myocardial failure in two Great Danes

Two Great Danes were evaluated for signs of congestive heart failure. Dilated cardiomyopathy was diagnosed in each dog. Both dogs were diagnosed concurrently with primary hypothyroidism. Following appropriate supplementation with levothyroxine, both dogs showed significant improvement in myocardial contractility, as demonstrated by increased fractional shortening and reductions in left atrial size, and left ventricular end-systolic and diastolic diameters. These observations suggest that hypothyroidism may lead to myocardial failure in Great Danes that is partially or fully reversible following thyroid hormone replacement therapy, and that hypothyroidism should be considered in all Great Danes presenting with systolic failure.

High prevalence of autoimmune thyroid disease in pulmonary arterial hypertension

STUDY OBJECTIVES

An association between thyroid disease and pulmonary arterial hypertension (PAH) has been reported, yet the pathogenetic relationship between these conditions remains unclear. Because immune system dysfunction may underlie this association, we sought to determine the prevalence of autoimmune thyroid disease (AITD) in patients with PAH.

DESIGN AND SETTING

Prospective observational study at a single academic institution.

PATIENTS

Sixty-three consecutive adults with PAH (ie, sustained pulmonary artery systolic pressure, > 25 mm Hg) were evaluated for clinical, biochemical, and serologic features of AITD.

MEASUREMENTS

Thyroid gland dysfunction was determined by clinical examination for goiter, and by biochemical measurements of thyrotropin and free thyroxine. Immune system dysfunction was determined by serologic measurements of antibodies to thyroglobulin and thyroid peroxidase. First-degree family history of AITD also was ascertained in order to investigate for genetic clustering of autoimmunity.

RESULTS

Thirty-one patients (49%; 95% confidence interval [CI], 37 to 62%) received diagnoses of AITD. Eighteen patients were newly diagnosed, and 9 patients required the initiation of pharmacologic treatment. There was no chronologic relationship between the diagnosis or treatment of PAH and that of AITD. Sixteen patients (25%; 95% CI, 15 to 36%) had 24 first-degree family members with AITD.

CONCLUSIONS

Approximately half of the patients with PAH have concomitant AITD. These two conditions may be linked by a common immunogenetic susceptibility, and the elucidation of this association may advance the understanding of the pathophysiology and treatment of PAH. Systematic surveillance for occult thyroid dysfunction in patients with PAH may prevent the hemodynamic exacerbation of right heart failure.

Inverse correlation between thyroid function and hemostatic markers for coronary heart disease in obese children and adolescents

BACKGROUND

Childhood obesity may be associated with thyroid dysfunction. Both obesity and hypothyroidism are related to increased risk of coronary heart disease (CHD) in adults through high levels of serum lipids and/or hemostatic abnormalities.

OBJECTIVE

To investigate a possible relationship between thyroid function and hemostatic markers for CHD in obese children and adolescents.

STUDY DESIGN

Thirty-nine obese children and adolescents were investigated for thyroid function and markers for CHD after overnight fast. Thyroid hormones were measured by radioimmunoassay. Factor VII coagulant activity (VIIc) and factor VIII coagulant activity (VIIIc) were determined using one stage clotting assays; fibrinogen was measured according to the method of Clauss; von Willebrand factor antigen (vWF-Ag), tissue type plasminogen activator antigen (tPA-Ag), and plasminogen activator inhibitor-1 antigen (PAI-1-Ag) were determined by ELISA.

RESULTS

We found a significant inverse correlation between fT4 and factor VIIc (r = -0.33, p = 0.03) and fibrinogen (r = -0.35, p = 0.02), which remained significant after adjustment for body fat mass. Factor VIIIc (r = -0.26, p = 0.066) and vWF-Ag (r = -0.28, p = 0.053) tended to be correlated negatively to fT4. fT4 did not correlate with tPA-Ag and PAI-1-Ag. fT3 was inversely related to factor VIIc (r = -0.3, p = 0.039), which was not independent of body fat mass, and showed a less impressive negative correlation with fibrinogen (r = -0.27, p = 0.058). fT3 did not correlate with vWF-Ag, tPA-Ag, or PAI-1-Ag. There was no relationship between TSH and the determined hemostatic markers.

CONCLUSION

Our study demonstrates a close relationship between thyroid function and hemostatic markers for CHD in obese children and adolescents and suggests that thyroid dysfunction is associated with an unfavorable hemostatic state even in pediatric patients.