Subclinical Thyrotoxicosis and Cardiovascular Risk: Assessment of Circulating Endothelial Progenitor Cells, Proangiogenic Cells, and Endothelial Function

BACKGROUND

Subclinical thyrotoxicosis (SCT) is defined by low or undetectable thyroid-stimulating hormones and normal thyroid hormones. The treatment of SCT is uncertain despite being associated with increased cardiovascular risk (CVR) and mortality. Circulating endothelial progenitor cells (cEPCs) and circulating angiogenic cells (CACs) have been found to be reduced in conditions with CVR. We aimed to evaluate whether endothelial function and cEPC and CAC counts were reduced in SCT and to study the in vitro effect of triiodothyronine (T3) on proangiogenic cell (PAC) function from young healthy controls.

METHODS

cEPCs (quantified by flow cytometry, 20 SCT/20 controls), CACs following in vitro cultures (15 SCT/14 controls), paracrine function of CACs, endothelial function by flow-mediated dilation (FMD, 9 SCT/9 controls), and the effect of T3 on apoptosis and endothelial nitric oxide synthase (eNOS) expression in PACs were studied.

RESULTS

p < 0.001, CD133⁺/VEGFR-2⁺ 0.4 (0.0-0.7) vs. 0.6 (0.0-4.6), p = 0.009, CD34⁺/VEGFR-2⁺ 0.3 (0.0-1.0) vs. 0.7 (0.1-4.9), p = 0.002; while CAC count was similar. SCT predicted a lower cEPC count after adjustment for conventional CVR factors. FMD was lower in SCT subjects versus controls (% mean ± SD, 2.7 ± 2.3 vs. 6.1 ± 2.3, p = 0.005). In vitro studies showed T3 increased early apoptosis and reduced eNOS expression in PACs.

CONCLUSIONS

In conclusion, SCT is associated with reduced cEPC count and FMD, confirming increased CVR in SCT. Future outcome trials are required to examine if treatment of this subclinical hyperactive state improves cardiovascular outcome.

CLINICAL TRIAL REGISTRATION

http://www.controlled-trials.com/isrctn/, identifier ISRCTN70334066.

Behavioral assessment of children and adolescents with Graves' disease: A prospective study

Previous studies have identified frequent comorbid neuropsychiatric disorders and conditions in adults with thyrotoxicosis. These studies are scarce or even lacking in pediatric population. This work aimed to study the behavior of children and adolescents with Graves’ disease (GD). This study included 35 children with GD (boys = 15; girls = 25; mean age: 11.45±1.50yrs) and 40 healthy children (boys = 20; girls = 20; mean age: 12.54±1.62yrs). Behavior was assessed using Child Behavior Checklist (CBCL). Children with GD were assessed during periods of thyroid hormone elevation (active disease) and normalized thyroid hormones (with anti-thyroid drugs or ATDs). Compared to healthy children, patients during periods of thyroid hormone elevation (74.29%) and normalized thyroid hormones (31.43%) had higher frequencies of behavioral abnormalities and scorings of total CBCL scale (P = 0.01; P = 0.04, respectively) and its subscales’ [Anxious/Depressed (P = 0.02; P = 0.04), Withdrawn/Depressed (P = 0.03; P = 0.04) and Somatic Complaints (P = 0.03; P = 0.127) and Social (P = 0.01; P = 0.225), Thought (P = 0.01; P = 0.128) and Attention (P = 0.01; P = 0.01) problems], indicating internalizing and externalizing problems. The majority of patients had at least two different behavioral problems. Marked improvement was found during period of normalized thyroid hormones (P = 0.001). Correlation analyses showed significant associations between total CBCL scoring and age at onset (P = 0.01; P = 0.001) and lower concentrations of thyroid stimulating hormone (TSH) (P = 0.001; P = 0.04) and higher concentrations of free thyroxine (fT4) (P = 0.01; P = 0.02), triiodothyronine (fT3) (P = 0.01; P = 0.03) and thyrotropin receptor antibodies (TRAbs) (P = 0.001; P = 0.01) during periods of thyroid hormone elevation and normalized thyroid hormones, respectively. Multiple linear regression analysis showed that "at presentation" lower concentrations of TSH (P = 0.001; P = 0.03) and higher concentrations of fT4 (P = 0.001, P = 0.01), fT3 (P = 0.01; P = 0.06) and TRAbs (P = 0.001; P = 0.001) were predictors of behavioral problems during periods of active disease and normalized thyroid hormones. We conclude that GD is associated with higher frequencies and severities of anxiety, depression and inattention during periods of thyroid hormone elevation as well as normalized thyroid hormones with ATDs. Therefore, early diagnosis and optimizing management are required to improve children’s social life.

A pregnant woman with an autonomously functioning thyroid nodule: a case report

BACKGROUND

The epidemiology and natural history of autonomously functioning thyroid nodules (AFTNs) have not been elucidated. Here we report the pregnant Japanese woman with an AFTN.

CASE PRESENTATION

The patient was a 31-year-old woman who was hospitalized due to the placenta previa associated with threatened abortion at the 16 weeks of her third pregnancy. At her second pregnancy, she was euthyroid but had a single, 2.3 cm nodule on her right thyroid lobe. Her thyroid hormone level was trended increased with her pregnancy progression, and the thyrotoxic state was remained after delivery. Before her third pregnancy, her hyper-vascular nodule enlarged to 3.4 cm at regular monitoring. When she visited our hospital, she was at 16 weeks of pregnancy and had thyrotoxicosis with negative TSH-receptor antibody. She delivered a baby weighing 2615 g without hypothyroidism at 39 weeks of pregnancy by natural delivery. After delivery, a ^99mTc scintigram showed a hot spot in her right thyroid lobe. She was diagnosed with AFTN and treated with methimazole while nursing.

CONCLUSIONS

This case showed that hCG stimulation during pregnancy caused thyroid nodule enlargement and enhanced thyroid hormone production. The pregnancy could be the pathological stimulus and provides chance to diagnosis for AFTNs.

Thyroid dysfunction following pregnancy and implications for breastfeeding

Subclinical autoimmune thyroiditis exacerbates after delivery through immune rebound mechanisms and results in 5 types of thyroid dysfunction. The prevalence of postpartum thyroid dysfunction is around 5% in mothers in the general population. Typically, an exacerbation induces destructive thyrotoxicosis followed by transient hypothyroidism, known as postpartum thyroiditis. Late development of permanent hypothyroidism is found frequently and patients should be followed up once every one to two years. Destructive thyrotoxicosis in postpartum thyroiditis should carefully be differentiated from post-partum Graves' disease. Postpartum thyroiditis typically occurs 1-4 months after parturition whereas Graves' disease develops at 4-12 months postpartum. Anti-TSH receptor antibodies (TRAb) are typically positive and thyroid blood flow is high in Graves' disease, whereas these features are absent in postpartum thyroiditis. Postpartum Graves' disease should be treated with antithyroid drugs.

Diagnostic testing for Graves' or non-Graves' hyperthyroidism: A comparison of two thyrotropin receptor antibody immunoassays with thyroid scintigraphy and ultrasonography

OBJECTIVE

Graves' disease (GD) is the most common cause of hyperthyroidism. In many cases, when the aetiological diagnosis of GD is not evident based on the clinical evaluation and thyroid function testing, it may become challenging to distinguish Graves' hyperthyroidism from other forms of thyrotoxicosis. The current study was primarly carried out to compare the diagnostic effectiveness of two TSH receptor antibody immunoassays (IMAs), ultrasonography and thyroid scintigraphy in hyperthyroidism scenario.

METHODS

We retrospectively analysed consecutive patients with newly diagnosed and untreated thyrotoxicosis who underwent thyroid functional tests, both TRAb and TSI measurements, thyroid scintigraphy and ultrasonography. TRAb assessment was carried out by Kryptor^® compact PLUS, while TSI by Immulite^® . Echo pattern 3 corresponded to 'thyroid inferno', and the final diagnosis of GD vs non-Graves' hyperthyroidism was made according to the thyroid scan (qualitative scintigraphy). Receiver operating characteristic (ROC) curves were drawn using the final diagnosis as reference. Clinical sensitivity and specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated for all the tests.

RESULTS

A total of 124 untreated hyperthyroid patients were included in our study (GD, n = 86 vs non-Graves' hyperthyroidism, n = 38). ROC curves showed that the optimal cut-off values associated with the highest diagnostic sensitivity and specificity was 0.7 IU/L for TRAb Kryptor^® (93 [85.4-97.4] and 86.8 [71.9-95.5]) and 0.1 IU/L for TSI Immulite^® (94.2 [86.9-98.1] and 84.2 [68.7-93.9]), respectively. For the echo pattern 3, we found a good sensitivity (92.1%) and a high PPV (95.2%) but a quite low specificity value (69.8%) and a relative low NPV (57.5%). For thyroid scintigraphy, the TcTU cut-off value of 1.3% corresponded to the best limit for sensitivity and specificity in our patients (95.3 [88.5-98.7] and 96.4 [81.6-99.4]). The Passing-Bablok regression equation and the Bland-Altman test showed a great degree of correlation and agreement existed between TRAb Kryptor^® and Immulite^® TSI results.

CONCLUSIONS

Thyroid scintigraphy remains the most accurate method to differentiate causes of thyrotoxicosis. However, TRAb assays can be alternatively adopted in this setting, limiting the use of thyroid scintigraphy (TcTU evaluation) to TRAb-negative patients. Thyoid US is less accurate than both TRAb/TSI and thyroid scintigraphy, but the 'thyroid inferno' pattern provides a high PPV for GD.

A Thyroid Hormone-Independent Molecular Fingerprint of 3,5-Diiodothyronine Suggests a Strong Relationship with Coffee Metabolism in Humans

Background: In numerous studies based predominantly on rodent models, administration of 3,5-diiodo-L-thyronine (3,5-T2), a metabolite of the thyroid hormones (TH) thyroxine (T4) and triiodo-L-thyronine (T3), was reported to cause beneficial health effects, including reversal of steatohepatosis and prevention of insulin resistance, in most instances without adverse thyrotoxic side effects. However, the empirical evidence concerning the physiological relevance of endogenously produced 3,5-T2 in humans is comparatively poor. Therefore, to improve the understanding of 3,5-T2-related metabolic processes, we performed a comprehensive metabolomic study relating serum 3,5-T2 concentrations to plasma and urine metabolite levels within a large general population sample. Methods: Serum 3,5-T2 concentrations were determined for 856 participants of the population-based Study of Health in Pomerania-TREND (SHIP-TREND). Plasma and urine metabolome data were generated using mass spectrometry and nuclear magnetic resonance spectroscopy, allowing quantification of 613 and 578 metabolites in plasma and urine, respectively. To detect thyroid function-independent significant 3,5-T2-metabolite associations, linear regression analyses controlling for major confounders, including thyrotropin and free T4, were performed. The same analyses were carried out using a sample of 16 male healthy volunteers treated for 8 weeks with 250 μg/day levothyroxine to induce thyrotoxicosis. Results: The specific molecular fingerprint of 3,5-T2 comprised 15 and 73 significantly associated metabolites in plasma and urine, respectively. Serum 3,5-T2 concentrations were neither associated with classical thyroid function parameters nor altered during experimental thyrotoxicosis. Strikingly, many metabolites related to coffee metabolism, including caffeine and paraxanthine, formed the clearest positively associated molecular signature. Importantly, these associations were replicated in the experimental human thyrotoxicosis model. Conclusion: The molecular fingerprint of 3,5-T2 demonstrates a clear and strong positive association of the serum levels of this TH metabolite with plasma levels of compounds indicating coffee consumption, therefore pointing to the liver as an organ, the metabolism of which is strongly affected by coffee. Furthermore, 3,5-T2 serum concentrations were found not to be directly TH dependent. Considering the beneficial health effects of 3,5-T2 administration observed in animal models and those of coffee consumption demonstrated in large epidemiological studies, one might speculate that coffee-stimulated hepatic 3,5-T2 production or accumulation represents an important molecular link in this connection.

Thyroid function related symptoms during levothyroxine monotherapy in athyreotic patients

Previous reports by us and other investigators showed that among athyreotic patients on levothyroxine (LT₄) following total thyroidectomy patients with normal serum thyroid-stimulating hormone (TSH) levels had mildly low serum free triiodothyronine (FT₃) levels, whereas patients with mildly suppressed serum TSH levels had normal serum FT₃ levels and patients with strongly suppressed serum TSH had elevated serum FT₃ levels. The objective of this study was to clarify which of these three patient groups are closer to their preoperative euthyroid condition based on reported subjective symptoms. We prospectively studied 148 consecutive euthyroid patients with papillary thyroid carcinoma who underwent a total thyroidectomy. Symptoms reflecting thyroid function documented preoperatively and following 12 months of LT₄ after thyroidectomy were compared. In 65 patients with strongly suppressed TSH levels significant changes in symptoms with tendencies towards thyrotoxicosis were seen with regards to heat and cold tolerance (p < 0.01), bowel movements (p < 0.05), and hand tremors (p < 0.05). In 33 patients with normal TSH levels, significant changes in symptoms with tendencies towards hypothyroidism were seen with regards to heat and cold tolerance (p < 0.05) and activity (p < 0.05). Lastly, in 50 patients with mildly suppressed TSH levels and FT₃ levels equivalent to preoperative levels, all symptom items remained equivalent to their preoperative levels. Symptoms reflecting thyroid function in patients on LT₄ following total thyroidectomy suggested that patients with mildly suppressed TSH levels were closest to a euthyroid status. These data provide useful findings regarding the management of patients following total thyroidectomy.

Thyrotoxicosis Involves β2-Adrenoceptor Signaling to Negatively Affect Microarchitecture and Biomechanical Properties of the Femur

Background: Thyrotoxicosis increases bone turnover, resulting in net bone loss. Sympathetic nervous system (SNS) activation, via β2-adrenoceptor (β2-AR) signaling, also has osteopenic effects. Because thyroid hormones (TH) interact with the SNS to regulate several physiological processes, we hypothesized that this interaction also occurs to regulate bone mass. Previous studies support this hypothesis, as α2-AR knockout (KO) mice are less susceptible to thyrotoxicosis-induced osteopenia. Here, we evaluated whether TH-SNS interactions in bone involve β2-AR signaling. Methods: Thyrotoxicosis was induced in 120-day-old female and male mice with β2-AR gene inactivation (β2-AR^-/-) by daily treatment with supraphysiological doses of triiodothyronine (T3) for 12 weeks. The impact of thyrotoxicosis on femoral bone microarchitecture, remodeling, fracture risk, and gene expression of the receptor activator of nuclear factor-kappa-B (RANK)-RANK ligand (RANKL)-osteoprotegerin (OPG) pathway was evaluated. In addition, the effect of the β2-AR-specific agonist clenbuterol (CL) on cAMP accumulation was determined in osteoblastic (MC3T3-E1) cells treated with T3 and/or 17β-estradiol (E2). Results: Thyrotoxicosis negatively affected trabecular bone microarchitecture in wild-type (WT) females, but this effect was milder or nonexistent in β2-AR^-/- animals, whereas the opposite was seen in males. T3 treatment increased the femoral RANKL/OPG mRNA ratio and the endosteal perimeter and medullary area of the diaphysis in WT females and males, but not in β2-AR^-/- mice, suggesting that T3 promotes endosteal resorption in cortical bone, in a mechanism that involves β2-AR signaling. T3 treatment increased endocortical mineral apposition rate only in WT females but not in β2-AR^-/- mice, suggesting that TH also induce bone formation in a β2-AR signaling-dependent mechanism. T3 treatment decreased femoral resistance to fracture only in WT females, but not in KO mice. E2 and CL similarly increased cAMP accumulation in MC3T3-E1 cells; whereas T3 alone had no effect, but it completely blocked E2-stimulated cAMP accumulation, suggesting that some T3 effects on bone may involve E2/cAMP signaling in osteoblasts. Conclusions: These findings sustain the hypothesis that T3 interacts with the SNS to regulate bone morphophysiology in a β2-AR signaling-dependent mechanism. The data also reveal sex as an important modifier of skeletal manifestations of thyrotoxicosis, as well as a modifier of the TH-SNS interactions to control bone microarchitecture, remodeling, and resistance to fracture.

Thyroid diseases and bone health

Thyroid hormones are essential for skeletal development and are important regulators of bone maintenance in adults. Childhood hypothyroidism causes delayed skeletal development, retarded linear growth and impaired bone mineral accrual. Epiphyseal dysgenesis is evidenced by classic features of stippled epiphyses on X-ray. In severe cases, post-natal growth arrest results in a complex skeletal dysplasia. Thyroid hormone replacement stimulates catch-up growth and bone maturation, but recovery may be incomplete dependent on the duration and severity of hypothyroidism prior to treatment. A severe phenotype characteristic of hypothyroidism occurs in children with resistance to thyroid hormone due to mutations affecting THRA encoding thyroid hormone receptor α (TRα). Discovery of this rare condition recapitulated animal studies demonstrating that TRα mediates thyroid hormone action in the skeleton. In adults, thyrotoxicosis is well known to cause severe osteoporosis and fracture, but cases are rare because of prompt diagnosis and treatment. Recent data, however, indicate that subclinical hyperthyroidism is associated with low bone mineral density (BMD) and an increased risk of fracture. Population studies have also shown that variation in thyroid status within the reference range in post-menopausal women is associated with altered BMD and fracture risk. Thus, thyroid status at the upper end of the euthyroid reference range is associated with low BMD and increased risk of osteoporotic fragility fracture. Overall, extensive data demonstrate that euthyroid status is required for normal post-natal growth and bone mineral accrual, and is fundamental for maintenance of adult bone structure and strength.

Variable Cold-Induced Brown Adipose Tissue Response to Thyroid Hormone Status

BACKGROUND

In addition to its role in adaptive thermogenesis, brown adipose tissue (BAT) may protect from weight gain, insulin resistance/diabetes, and metabolic syndrome. Prior studies have shown contradictory results regarding the influence of thyroid hormone (TH) levels on BAT volume and activity. The aim of this pilot study was to gain further insights regarding the effect of TH treatment on BAT function in adult humans by evaluating the BAT mass and activity prospectively in six patients, first in the hypothyroid and then in the thyrotoxic phase.

METHODS

The study subjects underwent 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) scanning after cold exposure to measure BAT mass and activity while undergoing treatment for differentiated thyroid cancer, first while hypothyroid following TH withdrawal at the time of the radioactive iodine treatment and then three to six months after starting TH suppressive treatment when they were iatrogenically thyrotoxic. Thermogenic and metabolic parameters were measured in both phases.

RESULTS

All study subjects had detectable BAT under cold stimulation in both the hypothyroid and thyrotoxic state. The majority but not all (4/6) subjects showed an increase in detectable BAT volume and activity under cold stimulation between the hypothyroid and thyrotoxic phase (total BAT volume: 72.0 ± 21.0 vs. 87.7 ± 16.5 mL, p = 0.25; total BAT activity 158.1 ± 72.8 vs. 189.0 ± 55.5 SUV*g/mL, p = 0.34). Importantly, circulating triiodothyronine was a stronger predictor of energy expenditure changes compared with cold-induced BAT activity.

CONCLUSIONS

Iatrogenic hypothyroidism lasting two to four weeks does not prevent cold-induced BAT activation, while the use of TH to induce thyrotoxicosis does not consistently increase cold-induced BAT activity. It remains to be determined which physiological factors besides TH play a role in regulating BAT function.

Hyperthyroidism

Hyperthyroidism is characterised by increased thyroid hormone synthesis and secretion from the thyroid gland, whereas thyrotoxicosis refers to the clinical syndrome of excess circulating thyroid hormones, irrespective of the source. The most common cause of hyperthyroidism is Graves' disease, followed by toxic nodular goitre. Other important causes of thyrotoxicosis include thyroiditis, iodine-induced and drug-induced thyroid dysfunction, and factitious ingestion of excess thyroid hormones. Treatment options for Graves' disease include antithyroid drugs, radioactive iodine therapy, and surgery, whereas antithyroid drugs are not generally used long term in toxic nodular goitre, because of the high relapse rate of thyrotoxicosis after discontinuation. β blockers are used in symptomatic thyrotoxicosis, and might be the only treatment needed for thyrotoxicosis not caused by excessive production and release of the thyroid hormones. Thyroid storm and hyperthyroidism in pregnancy and during the post-partum period are special circumstances that need careful assessment and treatment.

Prolonged and Severe Gestational Thyrotoxicosis Due to Enhanced hCG Sensitivity of a Mutant Thyrotropin Receptor

CONTEXT

Gestational thyrotoxicosis, whether associated with hyperemesis gravidarum or not, is thought to be due to excessive human chorionic gonadotropin (hCG) secretion.

CASE DESCRIPTION

We report here the second case of gestational thyrotoxicosis associated with hyperemesis gravidarum due to a mutation of the TSH receptor, providing thyroid hypersensitivity to hCG.

CONCLUSION

Severe and lasting gestational thyrotoxicosis with normal hCG concentration should lead to sequencing of the TSH receptor gene.

Increased expression of pro-angiogenic factors and vascularization in thyroid hyperfunctioning adenomas with and without TSH receptor activating mutations

Autonomously functioning thyroid nodules (AFTN) are known to receive an increased blood influx necessary to sustain their high rate of growth and hormone production. Here, we investigated the expression of hematic and lymphatic vases in a series of 20 AFTN compared with the contralateral non-tumor tissues of the same patients, and the transcript levels of proteins involved in the control of vascular proliferation, including the vascular endothelial growth factor (VEGF) and platelet-derived growth factors (PDGF) and their receptors and the endothelial nitric oxide synthase (eNOS). In parallel, the expression of the differentiation markers sodium/iodide symporter (NIS), thyroperoxidase (TPO), thyroglobulin (Tg), and TSH receptor (TSHR) was also investigated. The data were further analyzed comparing subgroups of tumors with or without mutations in the TSHR gene. Analysis by means of CD31 and D2-40 immunostaining showed in AFTN an increased number of hematic, but not lymphatic, vessels in parallel with an enhanced proliferation rate shown by increased Ki67 staining. Quantitative RT-PCR analysis revealed an increase of VEGF, VEGFR1 and 2, PDGF-A, PDGF-B, and eNOS expression in tumor versus normal tissues. Also, higher transcript levels of NIS, TPO, and Tg were detected. Comparison of the two subgroups of samples revealed only few differences in the expression of the genes examined. In conclusion, these data demonstrate an increased expression of angiogenesis-related factors associated with an enhanced proliferation of hematic, but not lymphatic, vessels in AFTNs. In this context, the presence of TSHR mutations may only slightly influence the expression of pro-angiogenic growth factors.

[Application of herbal medicine alba in treatment of patients with the pathology of thyroid]

High prevalence of hyperplastic and autoimmune diseases of thyroid in Ukrainian population is determined by endemic deficit of iodine and selenium. The aim of this research was to assess the place of biologically-active additions on the basis of herbal material containing an iodine and selenium in prophylaxis and treatment of thyroid pathology. During the six month period 55 patients received herbal preparation Alba twice a day. The levels of TSH, volume of thyroid, the sizes of nodular goiter (ultrasound investigation) were measured before and at the end of the investigation. The levels of thyroid stimulating antibodies to TSH receptor (AB-r TSH) were evaluated in patients with hyperthyroidism. The results of Alba application showed that in patients with thyroid pathology (diffuse nontoxic goiter, hyperthyroidism and chronic thyroiditis) it was possible to reduce the volume of thyroid, normalize its function, and decrease the level of AB-r TSH in diffuse toxic goiter. We also found approximately 20 % shortening of the time needed to get target level of TSH and finally the duration of treatment of thyrotoxicosis.

Thyroid hormone action on skin

PURPOSE OF REVIEW

To review the current understanding regarding thyroid hormone action on skin. To provide a historical context for the recent findings.

RECENT FINDINGS

Although direct thyroid hormone actions have been demonstrated on multiple aspects of cutaneous biology, rigorous study remains scant. Still, there is a slowly evolving literature supporting the concept that thyroid hormone can directly stimulate epidermis, dermis, and hair. That action may be accessed to treat cutaneous disease.

SUMMARY

Here, we review the literature regarding thyroid hormone action on skin along with skin manifestations of thyroid disease. We provide context for more recent findings of direct thyroid hormone stimulation of cutaneous cell proliferation in vitro and in vivo which may portend the use of thyroid hormone to treat cutaneous pathologies.

Determinants and outcome of amiodarone-associated thyroid dysfunction

OBJECTIVE

Amiodarone is frequently associated with thyroid dysfunction. Identifying predictors for amiodarone-associated thyroid dysfunction and assessing treatment outcome may aid clinicians in daily practice.

METHODS

We included 303 consecutive patients with amiodarone therapy for cardiac arrhythmias (260 with atrial fibrillation and 43 with ventricular arrhythmias). Thyroid function tests were performed every 6 months.

RESULTS

Mean age was 63 ± 12 years and 66% was male. After median follow-up of 3·3 (0·1-24) years, 23 (8%) patients developed amiodarone-associated thyrotoxicosis (incidence rate 1·9 per 100 person years) and 18 (6%) hypothyroidism (incidence rate 1·1 per 100 person years). The only predictor for amiodarone-associated thyrotoxicosis was age <62 years [HR = 2·4 (95% CI 1·0-5·7), P = 0·05]. Predictors for amiodarone-associated hypothyroidism were thyroid stimulating hormone >1·4 mU/l at baseline [HR = 5·1 (95% CI 1·1-22·4), P = 0·03], left ventricular ejection fraction <45% [HR = 3·8 (95% CI 1·1-13·3), P = 0·04] and diabetes mellitus at baseline [HR = 3·3 (95% CI 1·1-10·3), P = 0·04]. Gender was not a predictor for amiodarone-associated thyroid dysfunction. Five out of 12 (42%) patients with thyrotoxicosis exhibited spontaneous normalization of thyroid function on continuation of amiodarone therapy. Mean time to normalization in the total group was 6·2 ± 3·3 months, with no difference between continuing or discontinuing amiodarone (6·6 ± 3·8 vs 5·8 ± 2·8 months, P = 0·5).

CONCLUSIONS

During median follow-up of 3·3 years, the incidence of amiodarone-associated thyrotoxicosis was higher compared to hypothyroidism. Only general predictors for amiodarone-associated thyroid dysfunction were observed. Discontinuation of amiodarone did not influence treatment outcome.

Estrogens modulate RANKL-RANK/osteoprotegerin mediated interleukin-6 effect on thyrotoxicosis-related bone turnover in mice

Interleukin-6 has been shown to cause imbalance between bone resorption and formation in thyrotoxicosis. The aim of the present study was an attempt to estimate the influence of estrogens on thyrotoxicosis-related disturbances in bone turnover in relation to RANKL-RANK/osteoprotegerin system in IL-6 deficient mice. The study was performed on 56, 12-13 weeks old, female mice: C57BL/6J (wild-type; WT) and C57BL/6J (IL6-/-Kopf) (IL-6 knock-out; IL6KO). The mice were randomly divided into 8 groups with 7 mice in each one: 1. WT controls, 2. IL6KO controls, 3. WT mice with thyrotoxicosis, 4. IL6KO mice with thyrotoxicosis, 5. WT ovariectomized, 6. IL6KO ovariectomized, 7. WT ovariectomized mice with thyrotoxicosis, and 8. IL6KO ovariectomized mice with thyrotoxicosis. Experimental model of menopause was evoked by bilateral ovariectomy carried out in 8-9 weeks old mice. Thyrotoxicosis was induced by intraperitoneal injection of levothyroxine at a dose of 1 μg/g daily over 21 days. The serum levels of TRACP5b, osteocalcin, OPG, and RANKL were determined by ELISA. RANKL serum concentrations were elevated significantly in all groups of ovariectomized mice as compared to respective controls, however, in a minor degree in IL6KO thyrotoxic mice as compared to wild-type animals. Osteoprotegerin serum levels were significantly increased in all thyrotoxic groups of mice except ovariectomized IL6KO animals. To sum up, the results of the present study suggest that IL-6 plays a key role in stimulation of RANKL-RANK/OPG system and this effect is strongly enhanced in conditions of accelerated bone turnover such as thyrotoxicosis and/or estrogen depletion.

Toxic multinodular goiter with low radioactive iodine uptake

A 74-year-old woman was referred to our hospital for goiter and persistent thyrotoxicosis. She had no signs of ophthalmopathy. She was not taking thyroid hormone. Thyroid CT revealed multiple nodules. The thyroid gland was not detected on (99m)Tc scintigraphy, (123)I uptake rate was 4.5% at 24 hours without hot nodules, and aberrant goiter was negative. After partial thyroidectomy, she was treated with levothyroxine. TRAb was undetectable during the disease course, and focal destructive change or chronic lymphocytic thyroiditis on the pathological specimens was not evident. We report a rare case of toxic multinodular goiter with low radioactive iodine uptake.

[Cardiometric data as indications to surgical treatment of elderly and senile patients suffering from thyrotoxicosis]

On the basis of studying clinical symptoms of thyrotoxicosis in elderly patients and an analysis of results of investigation of the heart the authors marked out additional indications to surgical treatment of this category of patients. Results of surgical treatment of elderly and senile patients suffering from thyrotoxicosis are also described.

[Quality of life of patients before and after surgical treatment of diffuse toxic goiter]

Quality of life of 89 patients with diffuse toxic goiter was analyzed before surgical intervention and at different terms after thyroidectomy or terminal subtotal resection of the thyroid gland using questionnaire SF-36. It was found that quality of life of patients with diffuse toxic goiter was lower than that of respondents without such pathology. The indices of quality of life one year after thyroidectomy (terminal subtotal resection of the thyroid gland) remained depending on the duration of the disease and complications of thyrotoxicosis, became reliably larger as compared with preoperative level due to social activity and emotional state.

Effects of sex steroid hormones, thyroid hormone levels, and insulin regulation on thyrotoxic periodic paralysis in Chinese men

Our study is to determine the expression of thyroid hormone, sex hormone, insulin, and C-peptide in Chinese male patients with thyrotoxic periodic paralysis (TPP). This study covered 102 patients with hyperthyroidism from Xijing Hospital. According to whether occurrence of TPP or not, patients were divided into two groups (those that were hyperthyroid with and without TPP) that were, matched with age, blood pressure, urea, and creatinine. We found the body mass index (BMI) in patients with TPP was higher than that in pure hyperthyroidism patients. The levels of the total thyroxine (T4), free triiodothyronine (FT3), and free thyroxine (FT4) were significantly lower in patients with TPP compared with pure hyperthyroidism patients, while serum testosterone levels were higher compared with pure hyperthyroidism patients. Moreover, after glucose administration, the concentration of insulin at 60, 120, and 180 min were significantly higher in patients with TPP than those in pure hyperthyroidism patients. The insulin area under the curve (AUC) was significantly increased in patients with TPP compared with pure hyperthyroidism patients. The levels of thyroid hormone, sex hormone, and insulin were different in Chinese male patients with TPP compared to those with only hyperthyroidism.

[Antioxidant status of patients with thyrotoxicosis syndrome treated with the combined regimen containing epifamin]

The work purpose was research of degree of free-radical processes intensity and catalase activity in blood serum of patients with a thyreotoxicosis syndrome at traditional treatment and the combined therapy with epifamin. Patients (n=25) have been divided into 2 groups: the first group of patients--12 persons who are on traditional treatment (antithyreoid drugs, beta-adrenoblockers); the second group--13 persons, are padding to basic therapy received epifamin on 1 tablet (10 mg) 3 times a day 10-15 minutes prior to meal within 7 days. Patients with thyreotoxicosis syndrome had an intensification of free-radical oxidation that was traced at measurement of biochemiluminescence parameters in blood serum. At the combined therapy with epifamin less expressed intensity of free-radical processes, and also increasing of the general antioxidant activity of an organism that did not descend at traditional treatment was observed. At carrying out of standard therapy of thyreotoxicosis syndrome, including application of antithyreoid drugs and beta-adrenoblockers, catalase activity decreased, that unfavorable affected antioxidant potential of an organism. At the combined therapy with epifamin level of catalase activity, on the contrary, increased, that could influence positively on antioxidant protection of an organism.

Contribution of radioiodine uptake measurement and thyroid scintigraphy to the differential diagnosis of thyrotoxicosis

Both clinical and subclinical thyrotoxicosis can result from a wide range of disorders. Establishing the correct etiology underlying thyrotoxicosis is essential to direct treatment towards its specific pathophysiologic process. Based on clinical experience and guideline recommendations, radioiodine iodine uptake (RAIU) measurement and scintigraphy are often requested as the first-line investigation in thyrotoxic patients; however, their specific individual contribution to the differential diagnosis of thyrotoxicosis has not been previously investigated. In our study we aimed at evaluating the diagnostic role of RAIU measurement and scintigraphy in the management of thyrotoxicosis. A total of 108 patients with clinical and 42 patients with subclinical thyrotoxicosis were included in this retrospective study. All patients had RAIU measured at 24 hours after (131)I-iodide administration, followed by thyroid scintigraphy. Based on the combination of RAIU and scintigraphy, patients were classified as having diffuse toxic goiter (DTG) in 44% (the most common diagnosis), toxic adenoma in 15.9%, thyroiditis in 14%, and toxic multinodular goiter in 2.7%, while the pattern was inconclusive in 22.7% of all patients. When considering only patients with clinical thyrotoxicosis, the scan was inconclusive in 12.9% of patients whereas it was inconclusive in 47.6% of patients with subclinical thyrotoxicosis. There was a highly significant association between thyrotoxic status and scan result, with a statistically significant better performance of RAIU and scintigraphy in patients with clinical thyrotoxicosis when compared to patients with subclinical thyrotoxicosis considered as a whole (P<0.001). Instead, no statistically significant difference was observed between patients with subclinical thyrotoxicosis and TSH <0.1 mU/L and patients with TSH between 0.1 mU/L and 0.4 mU/L (P=0.191). In conclusion, we confirm the key role of RAIU and scintigraphy in the management of thyrotoxicosis and document its better performance in patients with clinical thyrotoxic status.

Thyroid hormones, their carrier proteins, and thyroid antibodies in the pleural effusion of two patients with graves' disease-induced thyrotoxicosis

INTRODUCTION

Concentrations of thyroid hormones, their carrier proteins, and thyroid antibodies in plasma have been extensively investigated, but those in pleural effusion have not. PATIENTS AND MEDTHODS: In the present study, we report, for the first time, the concentrations of thyroid hormones, their carrier proteins, and thyroid antibodies in the pleural effusion of two thyrotoxicosis patients with Graves' disease.

RESULTS

The pleural effusions were transudates. The concentrations of thyroid hormone carrier proteins, such as thyroxine-binding globulin (TBG), thyroxine-binding prealbumin (TBPA), and albumin (Alb) were approximately 30-50% of the plasma. The concentrations of total triiodothyronine (TT3), total tetraiodothyronine (TT4), free triiodothyronine (FT3), and free tetraiodothyronine (FT4) were approximately 15-40%, 45-55%, 45-75%, and 80-85% of the plasma, respectively. The concentration of thyroid stimulating hormone receptor antibody (TRAb) (equal to TSH-binding inhibitory immunoglobulins%; TBII%) was approximately 90% of the plasma.

CONCLUSION

If the pleural effusions were treated with diuretics, substantial quantity of thyroid hormones and thyroid antibodies in the pleural effusion may have returned to the plasma, and might exacerbate thyrotoxicosis. For patients with thyrotoxicosis and pleural effusion, thoracentesis should be considered. The present findings will contribute to the understanding and treatment of hyperthyroidism-induced pleural effusion.

Insulin resistance in subjects with a history of thyrotoxic periodic paralysis (TPP)

BACKGROUND

Hyperinsulinaemia has been suggested as an important factor for developing hypokalaemic paralysis in patients with thyrotoxic periodic paralysis (TPP). Since hyperinsulinaemia is a common feature of insulin resistance, there may be a causal relationship between insulin resistance and TPP.

OBJECTIVE

To compare insulin sensitivity between subjects with a history of TPP and others with a history of thyrotoxicosis without periodic paralysis.

METHODS

Insulin sensitivity measured by euglycaemic hyperinsulinaemic clamp and 75-g oral glucose tolerance test (OGTT) were performed nonselectively in 10 subjects with a history of TPP (TPP group) and 10 age- and sex-matched subjects with a history of simple thyrotoxicosis (control group). All participants had euthyroidism and fasting plasma glucose of < 5.55 mmol/l at the time of the study.

RESULTS

Body mass index and waist circumference of the TPP group were higher than that of the control group. One of 10 (10%) subjects in the TPP group and 6 of 10 (60%) in the control group had BMI of < 23 kg/m2. Areas under the curve (AUC) of plasma glucose after OGTT were comparable, while the AUC of serum insulin of the TPP group was higher than in the control group. The TPP group had lower insulin sensitivity than the control group.

CONCLUSION

The subjects with a history of TPP were more obese and had lower insulin sensitivity than those with a history of simple thyrotoxicosis. Insulin resistance with compensatory hyperinsulinaemia may be a key feature of the pathogenesis of TPP.

[Osteoporosis treatment in patients with hyperthyroidism]

Childhood thyroid hormone (T3) is essential for the normal development of endochondral and intramembranous bone and plays an important role in the linear growth and maintenance of bone mass. In adult, T3 stimulates osteoclastic bone resorption mediated primarily by TR alpha and local conversion by deiodinase D2 may play a role in local activation. TSH seems to be an inhibitor of bone resorption and formation. In thyrotoxicosis patients with Graves' disease, there is increased bone remodelling, characterized by an imbalance between bone resorption and formation, which results in a decrease of bone mineral density (BMD) and an increased risk for osteoporotic fracture. Antithyroid treatment is able to reduce dramatically the bone resorption and to normalize BMD reduction. But previous hyperthyroidism is independently associated with an increased risk for fracture. Although further studies relating to the mechanism for possible impaired bone strength in these patients will be needed, bisphosphonates may be beneficial treatment for prevention of bone fractures in patients with severe risk for fractures, such as post-menopausal women.

Gestational transient thyrotoxicosis

Gestational transient thyrotoxicosis refers to non-autoimmune hyperthyroidism in pregnant women and it is associated with hyperemesis gravidarum. During pregnancy, there are some alterations in thyroid gland, such as elevation of thyroxine binding globulin, increased iodium clearance in kidneys, and stimulation of thyroid gland by human chorionic gonadotropin. Hitherto, the pathophysiology underlying the development of gestational transient thyrotoxicosis has not been fully recognized. Studies showed that human chorionic gonadotropin, an agonist of thyroid stimulating hormone, may stimulate thyroid stimulating hormone receptor, leading to increased thyroid hormone. Diagnosis of gestational transient thyrotoxicosis is established based on inexistence history of previous hyperthyroidism, elevation of thyroid hormone, absence of hyperthyroid abnormalities signs on physical examination (such as: enlargement of thyroid gland, exophthalmia), and the absent of positive thyroid autoantibody. Generally, gestational transient thyrotoxicosis does not require medication, unless if hyperemesis gravidarum is present, thus the patient has to be hospitalized to receive intravenous rehydration, electrolyte correction and antiemetic medication. On cases with worsened or prolonged symptoms, anti-thyroid agents such as short term propiltiourasil is needed.

Ghrelin and GHRP-6-induced ACTH and cortisol release in thyrotoxicosis

Thyrotoxicosis might alter the hypothalamic-pituitary-adrenal (HPA) axis. We evaluated the effects of ghrelin and GHRP-6 on the HPA axis in 20 hyperthyroid patients and in 9 controls. Mean basal cortisol (microg/dl) and ACTH (pg/ml) levels were higher in hyperthyroidism (cortisol: 10.7 +/- 0.7; ACTH: 21.5 +/- 2.9) compared to controls (cortisol: 8.1 +/- 0.7; ACTH: 13.5 +/- 1.8). In thyrotoxicosis Delta AUC cortisol values (microg/dl.90 min) after ghrelin (484 +/- 80) and GHRP-6 (115 +/- 63) were similar to controls (ghrelin: 524 +/- 107; GHRP-6: 192 +/- 73). A significant increase in Delta AUC ACTH (pg/ml x 90 min) after ghrelin was observed in thyrotoxicosis (4,189 +/- 1,202) compared to controls (1,499 +/- 338). Delta AUC ACTH values after GHRP-6 were also higher, although not significantly (patients: 927 +/- 330; controls: 539 +/- 237). In summary, our results suggest that ghrelin-mediated pathways of ACTH release might be activated by thyroid hormone excess, but adrenocortical reserve is maintained.

[Effects of mercazolyl and L-thyroxine on the antiedematous activity of immunotropic preparations during development of toxic brain edema and swelling]

Dysfunction of thyroid gland plays an important role in the pathogenesis of brain edema and swelling. Toxic brain edema and swelling was modeled under condition of hypo- and hyperfunction of thyroid gland. Mercazolyl and L-thyroxine ambiguously influence the development of toxic brain edema and swelling in rats. L-thyroxin (35.7 microg/kg) favors increase in the water content in brain tissue, which can be considered as synergism with the edematous factor and the formation of brain tissue susceptibility to the development of brain edema and swelling. The administration of mercazolyl (5 mg/kg) and L-thyroxin (35.7 microg/kg) with thymogen (10 microg/kg), thymalin (1.2 mg/kg), cycloferon (0.5 mg/kg) results in decreasing brain tissue density as compared to intact animals. Dysfunction of the thyroid gland leads to changes in pharmacodynamics of immune preparations, which results in a decrease of their antiedematous activity.

3,5,3'-Triiodothyronine thyrotoxicosis due to increased conversion of administered levothyroxine in patients with massive metastatic follicular thyroid carcinoma

OBJECTIVE

Some patients with massive metastatic thyroid carcinoma exhibit T(3) thyrotoxicosis. We investigated the prevalence and cause of T(3) thyrotoxicosis and the clues to the diagnosis.

DESIGN

Serum free T(3) (FT(3)), free T(4) (FT(4)), and TSH were measured in patients with massive metastases from papillary, follicular, or medullary thyroid carcinomas (31, 20, and seven patients, respectively). Patients without recurrence served as controls. Thyrotoxic patients were reexamined 1 wk after withdrawal of levothyroxine. Type 1 and type 2 iodothyronine deiodinase (D1 and D2) activities were measured in three tumor tissues from thyrotoxic patients.

MAIN OUTCOME

The serum FT(3) level and FT(3)/FT(4) ratio in the follicular carcinoma (FC) group were significantly higher than those in the papillary carcinoma group or patients without recurrence. Four patients (20%) in the FC group but none in the other groups demonstrated T(3) thyrotoxicosis or a FT(3)/FT(4) ratio greater than 3.5. One week after withdrawal of levothyroxine, both FT(3) and FT(4) levels decreased. Retrospective measurements of FT(3) in frozen stored sera demonstrated that FT(3) exceeded the upper normal limit when FT(4) began to decrease but remained within the normal range. Tumor tissues showed high D1 and D2 activities.

CONCLUSIONS

Twenty percent of patients with massive metastatic FC exhibited T(3) thyrotoxicosis, most likely due to increased conversion of T(4) to T(3) by tumor expressing high D1 and D2 activities. Occasional measurement of serum FT(3) in addition to FT(4) and TSH is recommended in patients with massive metastatic FC, especially when serum FT(4) decreases on fixed doses of levothyroxine.

Effects of thyrotoxicosis and selective hepatic autonomic denervation on hepatic glucose metabolism in rats

Thyrotoxicosis is known to induce a broad range of changes in carbohydrate metabolism. Recent studies have identified the sympathetic and parasympathetic nervous system as major regulators of hepatic glucose metabolism. The present study aimed to investigate the pathogenesis of altered endogenous glucose production (EGP) in rats with mild thyrotoxicosis. Rats were treated with methimazole in drinking water and l-thyroxine (T(4)) from osmotic minipumps to either reinstate euthyroidism or induce thyrotoxicosis. Euthyroid and thyrotoxic rats underwent either a sham operation, a selective hepatic sympathetic denervation (Sx), or a parasympathetic denervation (Px). After 10 days of T(4) administration, all animals were submitted to a hyperinsulinemic euglycemic clamp combined with stable isotope dilution to measure EGP. Plasma triiodothyronine (T(3)) showed a fourfold increase in thyrotoxic compared with euthyroid animals. EGP was increased by 45% in thyrotoxic compared with euthyroid rats and correlated significantly with plasma T(3). In thyrotoxic rats, hepatic PEPCK mRNA expression was increased 3.5-fold. Relative suppression of EGP during hyperinsulinemia was 34% less in thyrotoxic than in euthyroid rats, indicating hepatic insulin resistance. During thyrotoxicosis, Sx attenuated the increase in EGP, whereas Px resulted in increased plasma insulin with unaltered EGP compared with intact animals, compatible with a further decrease in hepatic insulin sensitivity. We conclude that chronic, mild thyrotoxicosis in rats increases EGP, whereas it decreases hepatic insulin sensitivity. Sympathetic hepatic innervation contributes only to a limited extent to increased EGP during thyrotoxicosis, whereas parasympathetic hepatic innervation may function to restrain EGP in this condition.

Thyroid function disorders--Guidelines of the Netherlands Association of Internal Medicine

Thyroid function disorders are common with a female to male ratio of 4 to 1. In adult women primary hypothyroidism and thyrotoxicosis have a prevalence of 3.5/1000 and 0.8/1000, respectively. This guideline is aimed at secondary care providers especially internists, but also contains relevant information for interested general practitioners and gynaecologists. A multidisciplinary working group, containing delegates of professional and patient organisations, prepared the guideline. According to principles of 'evidence-based medicine' available literature was studied and discussed. Considering the availability and quality of published studies a practical advice was formulated. For a full overview of the literature and considerations the reader is referred to the original version of the guideline (accessible through NIV-net). In this manuscript we have aimed to provide the practicing internist with practical and 'as evidence-based as possible' treatment guidelines with respect to thyroid function disorders.

[Characteristics of pharmacological and toxic effects of verapamil during cardiac arrhythmia in thyrotoxic and hypothyroid rats]

Aim of this study was to investigate antiarrhythmic and toxic effects of verapamil in mice and rats with thyrotoxicosis and hypothyroidism. We found that changes of thyroid status lead to the increased sensitivity of animals to toxicity of verapamil. At single intraperitoneal introduction of verapamil, LD50 was 118 +/- 7,7 mg/kg for control euthyroid mice, 53 +/- 4,1 mg/kg for hypothyroid mice, and 77 +/- 6,5 mg/kg for thyrotoxic mice. Sensitivity of rat myocardium to arrhythmogenic effects of calcium chloride increased with development of thyrotoxicosis and hypothyroidism. Effective arrhythmogenic dose of CaCl2 was 200 mg/kg for euthyroid rats and 140 mg/kg for rats with thyroid dysfunction. Intravenous introduction of verapamil had antiarrhythmic activity in rats with experimental thyroid dysfunction but at a lower effective dose. Effective preventive dose of verapamil was 3 - 4,5 mg/kg for euthyroid rats and 2 - 2,5 mg/kg for rats with thyrotoxicosis and hypothyroidism. Effective dose of verapamil during rhythm disturbance was 3 mg/kg for control euthyroid rats and 1,5 - 2 mg/kg for rats with abnormal thyroid status. These results provide a basis for the new individual approach for treatment of patients with cardiac arrhythmia combined with thyroid dysfunction.

Significance of low thyroid-stimulating hormone in pregnancy

PURPOSE OF REVIEW

To describe the significance of low thyroid-stimulating hormone in pregnancy.

RECENT FINDINGS

Interpretation of thyroid function in pregnancy must be seen in the context of changes in thyroid economy associated with gestation. Improvements in thyroid-stimulating hormone assay methodology have resulted in accurate identification of low and suppressed thyroid-stimulating hormone in pregnancy, and recent studies of screening thyroid function in pregnancy have found an incidence of low thyroid-stimulating hormone in up to 18% of women. Normative gestational-related reference ranges for thyroid hormones, particularly thyroid-stimulating hormone and thyroxine, should be established to identify the higher as well as the lower limits of these analytes. The adverse obstetric and neonatal outcomes associated with hyperthyroidism due to Graves' disease mean that this must be differentiated from the more common cause of suppressed thyroid-stimulating hormone, i.e. gestational transient thyrotoxicosis. It is suggested that estimation of thyroid peroxidase antibodies may be a useful initial diagnostic strategy in the evaluation of women with a low or suppressed thyroid-stimulating hormone.

SUMMARY

In addition to identifying women with high thyroid-stimulating hormone levels at screening (with implications for child intelligence), establishing the cause of low thyroid-stimulating hormone will improve obstetric outcome in a number of pregnant women.

Muscle membrane excitability after exercise in thyrotoxic periodic paralysis and thyrotoxicosis without periodic paralysis

We evaluated whether the paralytic attacks in thyrotoxic periodic paralysis (TPP) are primarily due to the abnormal excitability of the muscle membrane caused by a preexisting latent abnormality or to the effects of thyroid hormone. The prolonged exercise (PE) test was used to evaluate muscle membrane excitability in 21 patients with TPP and 11 patients with thyrotoxicosis without paralytic attacks (Tw/oPP) in the hyperthyroid state. The PE tests were compared between the hyperthyroid and euthyroid states in five of the TPP and three of the Tw/oPP patients. Compared to 20 healthy subjects, a significant increase in compound muscle action potential (CMAP) amplitudes immediately after exercise and a significant time-dependent gradual decline in CMAP amplitudes starting from 20 min after exercise were observed in the TPP patients. A significant decline in CMAP amplitudes was also observed in the Tw/oPP patients but only at 50 min after exercise. All of the TPP and Tw/oPP patients had a tendency to improve in the euthyroid state; the PE tests remained abnormal only in the TPP patients. Paralytic attacks in TPP patients are due primarily to a preexisting latent abnormal excitability of the muscle membrane, possibly genetic in origin.

Polyuria of thyrotoxicosis: downregulation of aquaporin water channels and increased solute excretion

Thyrotoxicosis is a common disorder causing cardiovascular and renal irregularities. In this study, thyrotoxicosis was produced in rats by 14 days of daily thyroxine injection. This was associated with an increase in cardiac index, mean arterial pressure, and renal blood flow compared with euthyroid controls. Food and water intake along with urine output were significantly increased in the thyrotoxic rats compared with control animals associated with a significant increase in solute excretion. Polyuria and increased solute excretion still occurred even when food and water intake was equivalent. These renal responses were associated with significant decreases in AQP1 and AQP2 water channel expression in both the ad lib and paired intake studies in the cortex and inner medulla. The downregulation of AQP2 protein occurred in spite of equivalent plasma arginine vasopressin (AVP) in the ad lib and increased AVP in the paired feeding studies. Solute-free water reabsorption was greater in both the ad lib and paired thyrotoxic than euthyroid rats and was associated with increased Na-K-2Cl cotransporter expression. We propose that the AVP-independent downregulation of AQP2, the observed increase in renal arterial pressure, and decrease in filtration fraction contribute to polyuria the increased solute excretion in spite of enhanced ion transporters in thyrotoxicosis.

H-RAS gene expression in human multinodular goiter

The RAS protooncogene has an important, although not yet established role in thyroid neoplasia. In this study, we evaluated the H-RAS mRNA and protein levels in human samples of nontoxic and toxic multinodular goiter samples, according to serum TSH levels. The mean of H-RAS mRNA levels in nodules of nontoxic nodular goiter were significantly increased compared to nonnodular tissue (1.49+/-1.21 vs. 0.94+/-0.81 AU, P=0.016). Nine of the 18 specimens (50%) of nontoxic multinodular goiter exhibited increased levels of H-RAS mRNA. The increased H-RAS mRNA levels were paralleled by inRAcreased H-Ras protein levels in about 90% of the cases. Interestingly, no differences were observed in H-RAS expression between nodules and adjacent nonnodular tissue in toxic nodular goiters (0.58+/-0.27 vs. 0.58+/-0.20 AU, P=0.88). None of the 10 samples from toxic multinodular goiters exhibited overexpression of H-RAS. The H-RAS expression was positively correlated with thyroglobulin expression (r2=0.51; P=0.04). In conclusion, we demonstrated increased levels of H-RAS mRNA and protein in samples of nontoxic multinodular goiter, indicating that it might be involved in goiter pathogenesis. In contrast, H-RAS overexpression was not detected in any of the samples of toxic multinodular goiter, suggesting different mechanisms for cell proliferation in nodular goiter according to thyroid status.

[Analysis of intracellular proapoptotic (Bax, Bak) and antiapoptotic (Bcl-2, Bcl-XL) proteins expression in thyrocytes from young patients with immune and non-immune thyroid disorders]

Apoptosis one of the form of programmed cell death is a physiological occurrence, requisite to the correct function of every organism. This is an active process that proceeds with a participation of the cellular metabolism embracing the activation of genes and the synthesis of proteins. The signal to apoptosis can be started practically in every cell of our organism. Disturbances of the apoptosis regulation determine the essential link of the pathogenesis of many diseases, including autoimmune thyroid disorders. The aim of this study was to estimate the expression of proapoptotic (Bax, Bak) and antiapoptotic (Bcl-2, Bcl-XL) proteins in thyroid tissues from 12 patients with Graves' disease (GD), 10 with non-toxic nodular goitre (NTNG) and 10 with toxic nodular goitre (TNG). Criteria for qualification of Graves' patients: large goitre, ophthalmopathy, TRAb > 5 U/L, positive titre of anti-TPO and anti-TG antibodies and concentration of TSH <0.45 microIU/mL more the 2-3 months from onset of the disease. Detection of apoptotic proteins in thyroid follicular cells was performed by Western Blot. These analysis was confirmed by immunohistochemistry using monoclonal antibodies in DAB chromogene visuality and marked by Mayer's haematoxylin. Identification of antiapoptotic Bcl-2 and Bcl-XL molecules in the thyroid follicular cells revealed a higher expression of both proteins in patients with Graves' disease (+++; ++, respectively) in comparison to patients with NTNG (++/+; +) and TNG (++; +). The detection of proapoptotic molecules showed higher expression of Bak (++/+) and Bax (+) in Graves' thyroid tissues while Bax was in trace amount in NTNG (0/+) and TNG (0/+). We conclude that alteration in the expression of antiapoptotic and proapoptotic proteins on surface of thyroid follicular cells may play a role in the pathogenesis of thyroid autoimmune disorders. In addition, suppression of apoptosis in Graves' disease led to predominance for proliferation of thyroid follicular cells which is responsible for goitre formation.

Effects of CPU 86017 (chlorobenzyltetrahydroberberine chloride) and its enantiomers on thyrotoxicosis-induced overactive endothelin-1 system and oxidative stress in rat testes

OBJECTIVES

To study the effects of CPU 86017, a berberine derivative, and its four enantiomers on thyrotoxicosis-induced oxidative stress and the excessive endothelin-1 system in rat testes.

METHODS

Adult male SD rats were given high-dose L-thyroxin (0.2 mg/kg subcutaneously) once daily for 10 days to develop thyrotoxicosis. Subsets of the rats were treated with CPU 86017 or its four enantiomers (SR, SS, RS, and RR) once daily from day 6 to day 10. The alterations of redox, nitric oxide synthase, and endothelin-1 system in testes were examined by spectrophotometry and reverse transcriptase-polymerase chain reaction assay.

RESULTS

After 10 days of high-dose L-thyroxin administration, increased mRNA expression of prepro-endothelin-1 and endothelin-converting enzyme was observed in the rat testes, accompanied by an elevated inducible nitric oxide synthase activity and oxidative stress. CPU 86017 and its enantiomer SR significantly improved these abnormalities.

CONCLUSIONS

High-dose L-thyroxin results in an overactive endothelin-1 system and oxidative stress in adult rat testis. CPU 86017 and its enantiomer SR suppressed the excessive ET-1 system by improving oxidative stress, and SR exhibited more potent efficacy than CPU 86017 and other enantiomers.

Effects of different antioxidants on lipid peroxidation in brain homogenates, induced by L-thyroxine administration in rats

OBJECTIVE

It is known that thyrotoxicosis induces lipid peroxidation (LPO). In contrast, propylthiouracil (PTU), a thyrostatic drug is a well-known antioxidant. Also melatonin has been shown to protect against free radical-induced neuronal destruction. At the same time, it is generally accepted that the brain is the most vulnerable tissue to oxidative stress.

METHODS

The goal of the study was to examine the components of LPO, i.e., conjugated dienes (CD), malondialdehyde (MDA) and Schiff's bases (SB), in the brain of male Wistar rats. Two experiments were performed, with two control groups created for each experiment: Group 1--intact animals and Group 2--animals injected with 0.9% NaCl. In Experiment I, the animals received L-thyroxine (L-T4) in a dose of 100 microg/kg BW, i.p., daily, for two weeks (Groups 3-5). After one week of L-T4 treatment, the following agents were added during a subsequent week: Group 4--PTU in drinking water (45 mg/kg BW/day); Group 5--melatonin (5 mg/kg BW, daily). In Experiment II, lasting 7 days, the animals were divided into the following groups: Group 1--intact animals; Group 2--animals injected with 0.9% NaCl; Group 3--PTU in drinking water (45 mg/kg BW/day); Group 4--melatonin (5 mg/kg BW, daily).

RESULTS

In Experiment I, we observed a significantly higher SB level in saline treated animals and a significant increase in both CD and SB levels in rats treated with L-T4, compared to those in non treated control. CD levels were also elevated in rats treated with L-T4, compared to values in the saline only treated animals. Melatonin and PTU reduced CD levels and melatonin diminished SB levels, as compared to those in L-T4-treated rats. In Experiment II, we observed significantly higher CD, SB and MDA levels in saline treated rats, when compared to respective values in non treated control. Melatonin decreased CD levels, when compared to CD levels in both the non treated and saline injected controls. Additionally, melatonin reduced SB levels relative to change in the brains of saline treated rats. Furthermore, PTU decreased CD levels in brain homogenates compared to non-treated animals.

CONCLUSIONS

(1) L-thyroxine administration stimulates LPO in the rat brain; (2) All the examined antioxidants decrease LPO in L-T4-administered animals; (3) All the examined antioxidants reduce the basal LPO; 4) Stress, when induced by handling, intensifies oxidative processes in the organism.

Evaluation of alveolo-capillary permeability in thyrotoxicosis using Tc-99m DTPA aerosol scintigraphy

Surfactant secreted from type II pneumocytes plays an important role in alveolo-capillary permeability. In thyrotoxicosis, high levels of T3 receptors detected at these cells might affect the alveolo-capillary permeability due to increased serum thyroid hormone levels. The results by CO-diffusion capacity measurement in thyrotoxicosis are conflicting. Changes in alveolo-capillary membrane permeability resulting from thyrotoxicosis are not well established yet. This prompted us to investigate the alveolo-capillary permeability in thyrotoxic patients in comparison with CO-diffusing capacity. For this aim twenty-two non-smoking thyrotoxic patients (before treatment) and fifteen healthy voluntary controls underwent 99mTc-DTPA aerosol scintigraphy. CO-diffusing and pulmonary function tests were performed in all subjects. After ventilation of radiotracer through a nebulizer for 15 minutes, 30 dynamic images (1 frame/minute) were taken from both lungs. ROI's were drawn over both lung areas, and the time-activity curves were generated. Then clearance half time (CT1/2) for radioaerosol was obtained. CT1/2 of thyrotoxic patients did not differ from that of the controls: 77.9 +/- 25.9 min vs. 79.4 +/- 22.3 min; p > 0.05. Similar result was found for CO-diffusion parameters. Also there was no significant correlation between CT1/2 and CO-diffusion parameters. We concluded that in patients with thyrotoxicosis, the alveolo-capillary permeability is unaffected. Further experimental research is needed to establish the possible effects of thyroid hormones on alveolo-capillary membrane.

[Thyroid dysfunction in long-term amiodarone administration. Correlation of the antiarrhythmic activity of amiodarone with its effect on thyroid function]

Relationship between amiodarone-associated thyroid dysfunction and antiarrhythmic activity of amiodarone was studied in 27 patients (13 with hypothyroidism, 8 with hyperthyroidism, 6 with euthyroid hyperthyroxinemia). Amiodarone-associated hypothyroidism and euthyroid hyperthyroxinemia were not associated with loss of antiarrhythmic efficacy of amiodarone. Hypothyroidism did not require amiodarone withdrawal and therapy with L-thyroxin was conducted at the background of continued amiodarone intake. Achievement of euthyroid state was not followed by recurrence of heart rhythm disturbances. Development of amiodarone-associated thyrotoxicosis was accompanied with loss of antiarrhythmic efficacy of amiodarone in all cases. In 87.5% of patients with thyrotoxicosis correction of the thyroid status was conducted under conditions of continued amiodarone intake as this drug had been given because of life threatening arrhythmias or proven resistance to other antiarrhythmic therapy. In 12.5% of patients it was possible to substitute other drugs for amiodarone. Correction of thyroid status and achievement of euthyroidosis in these patients was associated with restoration of amiodarone antiarrhythmic activity.

[Features of osteopenic syndrome in diffuse toxic goiter]

AIM

To characterize action of thyroid hormones overproduction on bone mineral density.

MATERIAL AND METHODS

Pain intensity was graded according to 4-score scale, atraumatic fractures in the past were recorded, mineral bone density (MBD) was studied, TTH and T4 levels and biochemical indices of calcium-phosphorus and bone metabolism were studied, thyroid volume was calculated by J. Brunn (1981) and USI data in 116 patients with diffuse toxic goiter aged 20-65 years compared to 200 healthy controls matched by gender and age.

RESULTS

Pain in bones was registered in 79% examinees (1.8 +/- 0.2 scores, on the average). Atraumatic bone fractures were in 9.5% (8% in the controls). MBD reduction was revealed at densitometry in 71% patients with thyrotoxicosis. It was most frequent and severe (in UD--1.78 +/- 0.1 SD, in MD--2.1 +/- 0.1 SD) in patients with severe disease associated with intensive bone remodeling. Loss of MBD does not depend on DTG duration. Mild thyrotoxicosis had no negative effect on bone tissue. Significant differences between patients with thyrotoxicosis and drug euthyrosis by rate and severity of osteopenia were not observed.

CONCLUSION

Patients with DTG, especially in severe DTG, demand prophylactic measures concerning osteopenia immediately after diagnosis of thyrotoxicosis.

Chronic cardiac-specific thyrotoxicosis increases myocardial beta-adrenergic responsiveness

Whereas many cardiac symptoms of thyrotoxicosis resemble those of the hyperadrenergic state, circulating catecholamines are reduced or normal in this condition. To test the hypothesis that the thyrotoxic heart is hypersensitive to catechol-amines, we studied beta-adrenergic signaling in a transgenic (TG) mouse in which the human type 2 iodothyronine deiodinase (D2) gene is expressed in myocardium. Because D2 converts T4 to T3, the active form of thyroid hormone, the D2 TG mouse exhibits mild, chronic thyrotoxicosis that is limited to the myocardium. In the current study, we determined that cAMP accumulation in response to either norepinephrine or forskolin treatment was increased in isolated ventricular myocardiocytes and membrane-enriched fractions prepared from these D2 TG hearts as compared with wild type. This increase in adenylyl cyclase (AC) Vmax could not be explained by changes in AC isoform expression or changes in the long or short forms of stimulatory G-protein Gsalpha, which were approximately 10% decreased in D2 TG membranes. However, Western analysis and ADP-ribosylation studies suggest that the increase in AC Vmax is mediated by a decrease in the expression of inhibitory G proteins (Gialpha-3 and/or Goalpha). These data suggest that cardiac thyrotoxicosis leads to increased beta-adrenergic responsiveness of cardiomyocytes via alterations in the regulatory G-protein elements of the AC membrane complex.

The insulin-like growth axis in patients with autoimmune thyrotoxicosis: effect of antithyroid drug treatment

OBJECTIVE

Hyperthyroidism is associated with altered growth hormone (GH) secretion. Many patients with thyroid dysfunction experience several poorly described complications such as symptoms and signs also seen in patients with growth hormone deficiency (GHD). We have therefore prospectively evaluated a possible relationship between the thyroid function, body composition, leptin levels and insulin-like growth factor (IGF) related peptides in patients with Graves' disease. DESIGN, PATIENTS, AND MEASUREMENTS: In a prospective group of 24 fasting female patients with Graves' disease (mean age (CI 95%): 40 years (33-47)), we measured serum thyroxine, triiodothyronine, thyrotropine (TSH), TSH receptor antibodies, anti-thyroid peroxidase, leptin, body composition, body mass index (BMI) and IGF-related peptides at diagnosis and after 12 months of treatment with thiamazol (ATD).

RESULTS

In thyrotoxic patients IGF-I plus IGF-II correlated positively with IGFBP-3 at baseline (r = 0.90, p < 0.1 x 10(16)) and after 12 months follow-up (r = 0.87, p < 0.1 x 10(-16)). In the thyrotoxic state total IGF-I, IGF-II, IGF binding protein 3 (IGFBP-3) and acid-labile subunit (ALS) but not free IGF-I decreased significantly from 223 microg/L (189-260) (mean (CI 95%), 877 microg/L (801-953), 4165 microg/L (3772-4577) and 22 mg/L (18-26)) to 198 microg/L (172-226), 788 microg/L (711-865), 3431 microg/L (3135-3741) and 19 mg/L (16-26) (p <0.006), respectively, after 12 months of ATD despite an increase in BMI from 22 (21-23) to 23 kg/m(2) (22-25) (p < 0.0004) but no significant changes in leptin.

CONCLUSIONS

The complex IGF systems seemed intact in thyrotoxic patients but change in body composition and the regulation of leptin and insulin secretion during treatment of autoimmune thyroid disease influence IGF-related peptides leaving the patient in a state somewhat similar to partial GHD, but the mechanism behind these alterations remains unclear.

Radioiodine therapy in hyperthyroidism: inverse correlation of pretherapeutic iodine uptake level and post-therapeutic outcome

BACKGROUND

High iodine uptake levels are widely accepted as a condition for successful treatment with radioiodine (RAI). However, the existing data are controversial and the correlation of pretherapeutic RAI uptake level and outcome of RAI therapy has not yet been quantified. The aim of this study was to analyze the influence of RAI uptake on the outcome after RAI treatment and to estimate uptake-dependent success rates.

MATERIALS AND METHODS

We retrospectively analyzed 229 patients (m = 53, f = 176; age 64 +/- 14 years) suffering from toxic adenoma, multinodular goitre or Graves' disease, respectively. Clinical status and T3, fT4 and TSH levels were assessed 3, 6, 12 and 18 months after treatment. Successful treatment was defined as loss of hyperthyroidism 18 months after radioiodine therapy. Logistic regression was used to assess the relation between the maximum iodine uptake and the rate of success and hypothyroidism, respectively, after RAI treatment.

RESULTS

Overall, patients presented with pretherapeutic RAI uptake values between 17% and 100%. Eighteen months after RAI treatment, an euthyroid state was achieved in 136 patients (60%), hypothyroidism occurred in 47 patients (20%) and 46 patients (20%) remained hyperthyroid. The patients with the lowest pretherapeutic RAI uptakes showed the highest success rates. The overall success rate significantly decreased from 92% at low RAI uptakes to 57% at high uptakes (P = 0.002). This effect was found in the patients suffering from multinodular goitre as well as in the patients with Graves' disease.

CONCLUSION

In contrast to the current opinion, our results provide evidence that the pretherapeutic iodine uptake level and post-therapeutic outcome are inversely correlated.