Effects of Supra-Physiological Levothyroxine Dosages on Liver Parameters, Lipids and Lipoproteins in Healthy Volunteers: A Randomized Controlled Crossover Study.

Eprotirome, a liver specific thyroid hormone agonist, was shown to induce significant increases in markers of liver injury along with a modest decrease in atherogenic lipids and lipoproteins. To get more insight into whether these effects on liver parameters were compound specific or the effect of mimicking thyrotoxicosis, we studied the effects of supra-physiological levothyroxine dosages on liver parameters, lipids and lipoproteins. We used data of a single-blinded, randomized controlled crossover trial. Herein, healthy volunteers received levothyroxine or no medication for 14 days. Thyroid hormone excess did not induce clinically relevant changes in liver parameters, while significant reductions in total cholesterol, low-density lipoprotein-cholesterol as well as apolipoprotein-B levels were observed in the intervention periods compared with the control periods. Supra-physiological thyroid hormone levels did not induce clinically relevant increases in markers of liver injury after 2 weeks of exposure, while it reduced total cholesterol, low-density lipoprotein cholesterol and apolipoprotein B levels. This suggests that the effects of eprotirome on liver parameters in previous studies were either off-target and compound specific or due to drug-drug interaction at the level of the liver. The results of our study are relevant for the development of novel thyroid hormone agonists to reduce atherogenic lipoproteins.

Plasma Levels of Free Thyroxine and Risk of Major Bleeding in Bariatric Surgery.

BACKGROUND: In a recent study of patients using vitamin K antagonists, those with low free thyroxin (FT4) levels within the normal range had a 3- to 5-fold increased risk of major bleeding. We tested the hypothesis that low levels of preoperative FT4 within the reference range are associated with an increased risk of major bleeding during and after bariatric surgery. METHODS: The charts of 2,872 consecutive patients undergoing bariatric surgery were retrospectively screened for bleeding episodes. Patients with major bleeding until 1 month after surgery were compared to randomly selected control patients without bleeding, in a ratio of 1:4. We evaluated the association between preoperative FT4 levels and the risk of major bleeding by logistic regression. RESULTS: Seventy-two cases (2.5%) with major bleeding were identified and 288 controls were selected. The median plasma level of FT4 was 13 pmol/l (interquartile range: 12-14) in the cases as well as in the controls. No clear effect was observed of low levels of FT4 on the risk of major bleeding: odds ratio 1.48 (95% CI: 0.46-4.80) for patients with an FT4 level <11 pmol/l, 1.03 (0.49-2.18) for patients with an FT4 level <12 pmol/l, and 1.12 (0.65-1.94) for patients with an FT4 level <13 pmol/l as compared to patients with FT4 values greater than or equal to these cutoff levels. INTERPRETATION: We did not observe an increased risk of major bleeding with low levels of FT4 in patients undergoing bariatric surgery.

The Hypercoagulable state in Hyperthyroidism is mediated via the Thyroid Hormone ß Receptor pathway.

OBJECTIVE: Hyperthyroidism is associated with a hypercoagulable state, but the underlying mechanism is unknown. Patients with resistance to thyroid hormone (RTH) due to defective thyroid hormone receptor ß (TRß) exhibit elevated circulating thyroid hormones (TH) with refractoriness to TH action in TRß-expressing tissues. We tested the hypothesis that the hypercoagulable state in hyperthyroidism is mediated via the TRß. DESIGN: We conducted a cross-sectional study from November 2013 to January 2015 in 3 hospitals in the Netherlands and the United Kingdom. METHODS: Patients with RTH due to defective TRß (n=18), patients with hyperthyroidism (n=16) and euthyroid subjects (n=18) were included. TH concentrations and markers of coagulation and fibrinolysis were measured. Data are expressed as median [interquartile range]. RESULTS: Free thyroxine (FT4) levels were slightly higher in hyperthyroid patients than in RTH patients (53.9 [30.5-70.0] and 34.9 [28.4-42.2]pmol/l, respectively, P=0.042). Both groups had raised FT4 levels compared to euthyroid subjects (14.0 [13.0-15.8] pmol/l, P≤0.001). Levels of von Willebrand factor (VWF), factor (F) VIII, fibrinogen, and D-dimer were significantly higher in hyperthyroid patients than in RTH patients (VWF 231 [195-296] vs. 111 [82-140]%, FVIII 215 [192-228] vs. 145 [97-158]%, fibrinogen 3.6 [3.0-4.4] vs. 2.8 [2.5-3.2]g/L, D-dimer 0.41 [0.31-0.88] vs. 0.20 [0.17-0.26]mg/L, respectively, P≤0.001), while there were no differences between RTH patients and euthyroid controls. CONCLUSIONS: Parameters of coagulation and fibrinolysis were elevated in hyperthyroid patients compared to patients with RTH due to defective TRß, whereas these parameters were not different between euthyroid controls and RTH patients, despite elevated FT4 concentrations in RTH patients. This indicates that the procoagulant effects observed in hyperthyroidism are mediated via the TRß.

Under-reporting of venous and arterial thrombotic events in randomized clinical trials: a meta-analysis.

For the detection of unwanted outcomes of new interventions, physicians rely on adverse event reporting. We attempt to quantify the reported incidence of venous thromboembolism (VTE) and arterial thrombosis (AT) in randomized clinical trials (RCTs), and evaluate the extent of under-reporting. We selected all therapeutic RCTs published in the four highest-impact general medicine journals between January 2011 and July 2011. Patients were categorized according to VTE risk. The occurrences of VTE and AT, either as predefined outcome or adverse event, were assessed. We identified 131 RCTs. VTE and AT were not reported in 89 and 70 % of these studies, respectively. The raw-unweighted reported incidence in the 3 studies with predefined outcomes for VTE was 8.4 (7.8-9.1) per 1,000 person-years. In the 128 studies without predefined outcomes for VTE, (consisting of 322,029 individuals, including patients with cancer, inflammatory disease, cardiovascular disease, surgery, adding up to a follow-up >500,000 person-years), an incidence of 0.4 (0.4-0.5) per 1,000 person-years was found. The reported incidence of AT in 18 studies in which AT was part of predefined outcomes was 25.6 (24.9-26.3) per 1,000 person-years. In 92 studies without predefined outcomes for AT (231,638 individuals, follow-up >200,000 person-years,), the incidence was 2.5 (2.3-2.7) per 1,000 person-years. The incidence of VTE and AT in RCTs is highly under-reported. Uniform registration of adverse events, even when unlikely to be related to the intervention, is necessary to be able to inform physicians about the potential toxicities of new therapeutic strategies.

Major Haemorrhage during Vitamin K Antagonist Treatment: The Influence of Thyroid Hormone Levels.

BACKGROUND: Annually, approximately 1-3% of patients treated with vitamin K antagonists (VKA) suffer from major haemorrhage. Since high levels of free thyroxine (fT4) are associated with increased thrombosis risk, the aim was to assess whether low levels of fT4 contribute to major haemorrhage in patients under VKA treatment. METHODS: The FACTORS (Factors in Oral Anticoagulant Safety) study is a case-control study on patients receiving VKA treatment, including 110 cases with major haemorrhage. Controls were 220 matched participants treated with VKA without major haemorrhage. Odds ratios (OR) and 95% confidence intervals (95% CI) for the association of fT4 levels with major haemorrhage were calculated for different fT4 cutoffs by conditional logistic regression. RESULTS: In patients with an fT4 level below 13 pmol/l, the risk of major haemorrhage was 5-fold increased (OR = 5.1; 95% CI: 0.9-28.6) compared with patients with an fT4 level above 13 pmol/l. At a cutoff of 14 pmol/l, the risk was 3-fold increased (OR = 2.9; 95% CI: 1.0-8.5). High levels of fT4 did not affect bleeding risk. No clear effect of thyroid-stimulating hormone and thyroid peroxidase antibodies was seen on the risk of major haemorrhage. CONCLUSIONS: These results indicate that fT4 levels below 14 pmol/l play a role in the aetiology of major haemorrhage in VKA users.

Arterial and venous thrombosis in endocrine diseases.

Endocrine diseases have been associated with cardiovascular events. Both altered coagulation and fibrinolysis markers and thrombotic disorders have been described in several endocrine diseases. This review summarizes the evidence on the influence of thyroid diseases, cortisol excess and deficiency, pheochromocytoma, hyperparathyroidism, hyperaldosteronism, hyperprolactinemia, and growth hormone excess and deficiency; on parameters of hemostasis; and on arterial and venous thrombotic events. All these endocrine diseases do have, or may have, influence either on hemostasis or on the risk of thrombotic events. Future studies are needed to establish the clinical relevance of these associations.

Use of oral glucocorticoids and the risk of pulmonary embolism: a population-based case-control study.

BACKGROUND: Recently, endogenous glucocorticoid excess has been identified as a risk factor for VTE. Whether exogenous use of glucocorticoids is associated with an increased risk of VTE is unclear. We aimed to quantify the risk of symptomatic pulmonary embolism (PE) in patients using corticosteroids. METHODS: A case-control study using the PHARMO Record Linkage System, a Dutch population-based pharmacy registry, was conducted. Cases were 4,495 patients with a first hospital admission for PE between 1998 and 2008. Control subjects were 16,802 sex- and age-matched subjects without a history of PE. International Classification of Diseases codes for hospitalization were used to retrieve information on underlying conditions. RESULTS: The risk of PE was highest in the first 30 days of glucocorticoid exposure (adjusted OR, 5.9; 95% CI, 2.3-3.9) and gradually decreased with increasing duration of use (OR, 1.9; 95% CI, 1.3-2.9) for long-term users (> 1 year). Low-dose glucocorticoid use (prednisolone daily dose equivalent < 5 mg) carried a twofold increased risk of PE (OR, 1.8; 95% CI, 1.3-2.4), whereas a 10-fold increased risk was observed for the highest dose of glucocorticoids (prednisolone > 30 mg) (OR, 9.6; 95% CI, 4.3-20.5). Stratification for both duration and dose of glucocorticoid showed the highest risk of PE in recently started users compared with long-term users at the time of PE, irrespective of the dose. CONCLUSION: Patients treated with oral glucocorticoids may be at an increased risk of PE, especially during the first month of exposure. This hypothesis requires confirmation in future studies.

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.

The effect of hyperthyroidism on procoagulant, anticoagulant and fibrinolytic factors: a systematic review and meta-analysis.

Several coagulation and fibrinolytic parameters appear to be affected by thyroid hormone excess; however, the net effect on the haemostatic system remains unclear. We aimed to update our previous review and systematically summarise and meta-analyse the data by assessing the effects of thyrotoxicosis on the coagulation and fibrinolytic system in vivo . Data sources included MEDLINE (2006-2012), EMBASE (2006-2012), and reference lists. The sources were combined with our previous search containing studies from 1980-2006. Eligible studies were all observational or experimental studies. Two investigators independently extracted data and rated study quality. Weighted mean proportion and 95% confidence intervals were calculated and pooled using a fixed and a random-effects model. A total of 29 articles consisting of 51 studies were included, as in several articles more than one study was described. We included four intervention (before and after treatment in hyperthyroid patients), five cross-sectional (hyperthyroid subjects and euthyroid controls), and four experimental (before and after use of thyroid hormone in euthyroid subjects) medium/high quality studies for meta-analysis. We found that thyrotoxicosis shifts the haemostatic balance towards a hypercoagulable and hypofibrinolytic state with a rise in factors VIII and IX, fibrinogen, von Willebrand factor, and plasminogen activator inhibitor-1. This was observed in endogenous and exogenous thyrotoxicosis, and in subclinical as well as overt hyperthyroidism. We conclude that both subclinical and overt hyperthyroidism induce a prothrombotic state, which is therefore likely to be a risk factor for venous thrombosis.

Levels of prolactin in relation to coagulation factors and risk of venous thrombosis. Results of a large population-based case-control study (MEGA-study).

The pituitary hormone prolactin is thought to influence coagulation. We aimed to study the relation between prolactin levels, coagulation factors and risk of venous thrombosis (VT). We used data from a large population based case-control study into aetiology of first VT (MEGA-study). Prolactin levels were determined in 2,068 patients with VT and 2,785 age- and sex matched control subjects. The relation between levels of coagulation factors and prolactin was studied among the controls. In addition, odds ratios (OR) and 95% confidence intervals (95%CI) were calculated for the risk of VT for different cut-off points of prolactin levels based on percentiles determined in the controls. Restricted analysis was performed among cases in whom blood was sampled within six months after VT. We found a rise in factor VIII and von Willebrand factor with increasing levels of prolactin in the controls. An increased risk of VT was observed when blood was sampled within six months after thrombosis (OR 2.9, 95%CI 1.1-8.1) for prolactin levels above the 99th percentile (42.6 µg/l) relative to levels between the 20th to 80th percentile. When blood was sampled more than six months after VT no clear association could be observed (OR 1.3, 95%CI 0.7-2.3). In conclusion, we found a modest association between prolactin and symptomatic venous thromboembolism, particularly when blood was sampled close to the event. This may be explained by a causal relation or by prolactin being a marker of stress due to the thrombotic event.

The incidence of venous thromboembolism in patients with overt hyperthyroidism: a retrospective multicentre cohort study.

Hyperthyroidism is associated with several changes in the haemostatic system resulting in a hypercoagulable state. It is uncertain at this stage whether this leads to an increased risk of venous thromboembolism (VTE). The aim of this retrospective cohort study was to determine the risk of VTE in all patients with overt hyperthyroidism and to compare this to the risk of VTE in the general population. In three hospitals in the Netherlands, patients with biochemically confirmed hyperthyroidism caused by Graves' disease, multinodular goiter or toxic adenoma were included. All available electronic and handwritten records were examined. Primary outcome was the occurrence of VTE within six months before and until six months after the diagnosis of hyperthyroidism. We included a total of 587 patients. Five patients experienced a VTE during the study period, resulting in an incidence rate of 8.7 (95% CI 2.8 - 20.2) per 1,000 person-years. Three of these five patients had a first VTE (incidence rate for first VTE was 5.3 [95% CI 1.1 - 15.6] per 1,000 person-years). Incidence rates of VTE in the general population are between 0.6 and 1.6 per 1,000 person-years for first VTE and 0.7 and 1.8 per 1,000 person-years for all VTE. In conclusion, the incidence rate of VTE in patients with hyperthyroidism appears to be high. Future prospective studies are needed to further explore this possible association and to address its clinical implications.

[Screening for thyroid dysfunction in dyslipidaemia patients]. / Schildklierdiagnostiek bij dyslipidemie.

We describe 2 patients, a 49-year-old man presenting with dyspnoea and fatigue, and a 50-year-old woman referred for hypercholesterolaemia and hypertension. Both patients appeared to have hypothyroidism-induced dyslipidaemia. The lipid abnormalities resolved completely following thyroid hormone replacement therapy. Hypothyroidism is a well-known cause of secondary dyslipidaemia and may therefore predispose to the development of atherosclerotic disease. Measurement of thyroid hormone levels are, however, often not included in the screening of dyslipidaemia patients. The cases presented illustrate the insidious and diverse clinical presentations and diagnostic challenges of hypothyroidism. In addition, these cases demonstrate that clinical and biochemical screening for thyroid dysfunction is of paramount importance in all dyslipidaemia patients to prevent inappropriate initiation of lipid-lowering therapy.

The influence of pituitary, adrenal, and parathyroid hormones on hemostasis and thrombosis.

Endocrine disorders can influence the hemostatic balance. Abnormal coagulation test results have been observed in patients with abnormal hormone levels. The present review updates the available evidence on the influence of pituitary, adrenal, and parathyroid hormones on the coagulation and the fibrinolytic system, and their possible clinical implications. The literature supports a possible relevant clinical effect of the imbalance between coagulation and fibrinolysis on thrombotic events in endogenous Cushing's syndrome. An effect on markers of coagulation and fibrinolysis has been shown for hyperprolactinemia, growth hormone excess or deficiency, exogenous hypercortisolism, pheochromocytoma, primary hyperaldosteronism, and hyperparathyroidism. However, the clinical relevance is still unproven. Until definitive evidence is available, clinicians should be aware of the possibility that endocrine disorders may be risk factors for thrombotic events.

Prolactin and venous thrombosis: indications for a novel risk factor?

OBJECTIVE: Several acquired risk factors for venous thrombosis (VT) are associated with high prolactin levels. Our goal was to investigate VT risk for different levels of prolactin. METHODS AND RESULTS: We used data of a case-control study on leg vein thrombosis conducted between September 1999 and August 2006 at the Academic Medical Center, Amsterdam, the Netherlands. Prolactin was assessed in 187 cases (mean age, 57 years; range, 19 to 90) and 374 gender-matched controls (mean age, 57 years; range, 18 to 93). Odds ratios and 95% CI for VT risk were estimated based on several cutoff levels derived from prolactin levels in controls. Odds ratios for VT risk clearly increased with higher prolactin levels. For prolactin levels above the 75th percentile (8 µg/L), we found an odds ratio of 1.7 (95% CI 1.0 to 2.7) as compared with levels below the 50th percentile (6 µg/L). This further increased up to an odds ratio of 4.7 (95% CI 1.8 to 11.8) for prolactin levels above the 97.5th percentile (16 µg/L). The risk was most pronounced in premenopausal women. CONCLUSIONS: Our data suggest that prolactin levels are associated with VT in a dose-dependent fashion. Future studies are needed to evaluate the causality of this relationship.

Increasing levels of free thyroxine as a risk factor for a first venous thrombosis: a case-control study.

A hypercoagulable state exists in hyperthyroidism, but the association with venous thrombosis (VT) is not fully explored. We aimed to investigate VT risk for different plasma levels of thyroid hormones and thyroid antibodies. We used a case-control study on leg vein thrombosis conducted between September 1999 and August 2006 at the Academic Medical Center, Amsterdam, The Netherlands. Parameters of thyroid function were assessed in 190 cases (mean age, 57 years; range, 19-90 years) and 379 sex-matched controls (mean age, 56 years; range, 18-93 years). Odds ratios (ORs) and 95% confidence intervals (CIs) for VT risk were estimated according to several cutoff levels derived from plasma levels observed in controls. We found the risk of VT to gradually rise with increasing levels of free thyroxine (FT(4)). In the absence of traditional acquired risk factors, FT(4) levels above 17 pmol/L yielded a sex- and age-adjusted OR of 2.2 (95% CI, 1.2-4.2) for deep VT, which further increased up to an OR of 13.0 (95% CI, 1.1-154.1) for FT(4) levels above reference range. Our data suggest increasing levels of FT(4) to be a risk factor for VT and may have implications for both the prevention and management of this disease.

Hormones and cardiovascular disease: a shift in paradigm with clinical consequences?

Several endocrine disorders have been associated with an increased risk of cardiovascular disease (CVD) and mortality. In addition, even subtle hormonal disturbances may modulate the function of cardiovascular organs. In this article, we discuss in detail the contribution of thyroid hormones, cortisol, the somatotropic hormones, and prolactin in the development of CVD. We do not only discuss epidemiological evidence on the association between hormones and cardiovascular disease, but we also address possible pathophysiological mechanisms underlying this association. In fact, hormones can contribute to the development of CVD both indirectly by inducing secondary metabolic changes such as hypertension, insulin resistance, or dyslipidemia, and directly by modulation of cellular pathways that are important in the process of atherosclerotic plaque formation (atherogenesis), plaque instability, and thrombosis. To date several new therapeutic approaches that focus on the control of hormones at the tissue level, independently of their circulating levels, are being developed. These may offer new possibilities for cardiovascular risk reduction.

Hypercoagulable state in Cushing's syndrome: a systematic review.

CONTEXT: It has been debated whether an increased risk of venous thromboembolism (VTE) exists in patients with Cushing's syndrome. OBJECTIVE: We aimed to summarize published literature on the effects of endogenous hypercortisolism on coagulation and fibrinolysis, as well as on the clinical outcome of VTE. DATA SOURCES: We searched the MEDLINE and EMBASE databases up to July 2008. Review of reference lists further identified candidate studies. STUDY SELECTION: Two investigators independently performed study selection and data extraction. Eligible studies had to include Cushing's syndrome patients and either evaluate hemostatic parameters in comparison with control persons or posttreatment levels or describe the occurrence of VTE. DATA EXTRACTION: The Newcastle-Ottawa Scale was used to assess study quality. A scoring system divided studies into categories of low, medium and high quality. DATA SYNTHESIS: Of 441 identified publications, 15 reports were included. They contained information on eight cross-sectionals, two intervention, and eight cohort studies. No high-quality studies were identified. Hypercoagulability was suggested by high levels of factor VIII, factor IX, and von Willebrand factor and by evidence of enhanced thrombin generation. A risk of 1.9 and 2.5% was reported for VTE not provoked by surgery, whereas risk of postoperative VTE varied between 0 and 5.6%, with one outlier of 20%. VTE was reported as the cause of death in 0-1.9% of Cushing's syndrome patients. CONCLUSIONS: Available studies suggest a high risk of venous thrombosis in patients with Cushing's syndrome. Glucocorticoid-induced hypercoagulability as well as surgery and obesity almost certainly contribute to this thrombotic tendency.