Changes In Thyroid Hormone Levels Research Articles

Evaluation of oxidative stress and thyroid hormone status in hemodialysis patients in Gorgan

Aims:The aim of this study focused on serum malondialdehyde (MDA) levels and erythrocyte superoxide dismutase (SOD) and catalase (CAT) activities in hemodialysis patients and compared with control groups.Materials and Methods:Forty-five hemodialyzed patients and 45 control groups recruited in this study. Serum creatinine and urea, thyroid hormones (THs) levels and erythrocyte antioxidant enzyme activities were determined.Results:Hemodialysis (HD) patients showed higher levels of MDA than control groups (P < 0.01), but the levels of thyroxin (T3), free triiodothyronine (fT3), and free thyroxin (fT4), SOD and CAT were low in HD patients (P < 0.01). Serum T3, fT3, and fT4 levels were significantly negative correlated with MDA (P < 0.01).Conclusion:It is concluded that serum lipid peroxidation is markedly increased in HD patients. This means that elevated reactive oxygen species may interact with the lipid molecules in HD patients. HD may cause significant changes in TH levels. Thyroid-stimulating hormone level in HD patients is slightly similar to that of control groups. This suggests that thyroid is able to resynthesize for hormonal urinary losses.

Light-Regulated Thyroid Hormone Signaling Is Required for Rod Photoreceptor Development in the Mouse Retina.

Ambient light is both a stimulus for visual function and a regulator of photoreceptor physiology. However, it is not known if light can regulate any aspect of photoreceptor development. The purpose of this study was to investigate whether ambient light is required for the development of mouse rod photoreceptors. Newborn mouse pups (C57BL/6) were reared in either cyclic light (LD) or constant dark (DD). Pups were collected at postnatal day (P)5, P10, P17, or P24. We performed retinal morphometric and cell death analysis at P5, P10, and P17. Rhodopsin expression was assessed using immunofluorescence, Western blot, and quantitative RT-PCR analysis. Electroretinograms were performed at P17 and P24. Radioimmunoassay and ELISA were used to follow changes in thyroid hormone levels in the serum and vitreous. In the DD pups, the outer nuclear layer was significantly thinner at P10 and there were higher numbers of apoptotic cells at P5 compared to the LD pups. Rhodopsin expression was lower at P10 and P17 in DD pups. Electroretinogram a-waves were reduced in amplitude at P17 in the DD pups. The DD animals had lower levels of circulating thyroid hormones at P10. Light-mediated changes in thyroid hormones occur as early as P5, as we detected lower levels of total triiodothyronine in the vitreous from the DD animals. Drug-induced developmental hypothyroidism resulted in lower rhodopsin expression at P10. Our data demonstrate that light exposure during postnatal development is required for rod photoreceptor development and that this effect could be mediated by thyroid hormone signaling.

127 THYROID STIMULATING HORMONE LEVEL CHANGE DURING CONTROLLED OVARIAN STIMULATION

Women who undergo assisted reproductive technology (ART) are exposed to a supra-physiological hormonal environment, which can affect the hypothalamus-pituitary-thyroid axis. Understanding these changes can help us improve the outcomes of ART. In this study we discuss the changes of thyroid hormone levels during ovarian stimulation as part of intrauterine insemination (IUI) and compare hypothyroid and euthyroid patients. Fifty-two infertile women aged 22 to 40 who underwent induction ovulation (I/O) as part of IUI were enrolled in this study. Out of 52 patients, 13 had underlying thyroid disease receiving levothyroxine treatment, and their thyroid test results were normal (&lt;2.5) for more than 6 weeks and had taken fixed levels of levothyroxine for more than 6 weeks. The TSH levels were measured by electrochemiluminescence at 3 times: baseline TSH (before starting of I/O), the day of HCG administration, and 4 weeks after. The change of TSH levels during this period and its relationship with baseline hypothyroidism, oestradiol levels, and I/O and pregnancy outcome were studied. Mean central index, frequency percentage, the median, and dispersion of standard deviation and interquartile range (IQR) were used to describe the data. Statistical tests, including t-test and chi-square, were used to analyse the data. Mean difference and relative risk indices were used to measure the differences. There was a significant increase in TSH level at the time of hCG injection compared with basal TSH in hypothyroid patients under treatment, TSH increased from 1.61 ± 0.81 to 2.75 ± 1.86 (P = 0.045), and this increase was seen in TSH 4 weeks later from 1.61 ± 0.81 to 2.12 ± 0.87 (P = 0.026). However, there were not significant changes in thyroid hormone level during treatment in euthyroid patients. In hypothyroid patients who got pregnant, there was no significant increase in 3 TSH measurements. But for the patients with an unsuccessful cycle this increase was seen at the time of HCG injection and 4 weeks later in comparison with basal TSH, which was statistically significant: 1.55 ± 0.83 v. 2.97 ± 2.09 (P = 0.05) and 1.55 ± 0.83 v. 2.14 ± 0/99 (P = 0.039). But this change was not seen in euthyroid patients with successful and unsuccessful cycle results. The relationship between TSH level with oestradiol in both euthyroid and hypothyroid patients was not significant. There was not a significant correlation between the number of follicles bigger than 16 mm, the mean size of follicles, and endometrial thickness with TSH at the time of HCG injection in both hypothyroid and euthyroid patients. There was a negative and reverse correlation between endometrial thickness and TSH at the time of HCG injection, but it was not significantly different. (P = 0.05). In euthyroid patients who undergo I/O as part of IUI, we did not observe significant TSH level changes during I/O, but in controlled hypothyroid patients a rise in serum TSH levels was observed. The pregnancy rate between 2 euthyroid and controlled hypothyroid groups was not different.

Thyroid hormone supplementation following open-heart surgery in children

In patients undergoing open-heart surgery, abnormalities in thyroid hormone levels have been observed even in the absence of primary thyroid disease. These abnormal changes in thyroid hormone level and function have been found to be sufficient to affect myocardial performance and postoperative recovery. In the intensive care unit, postoperatively, it has been found that features such as low cardiac output, left ventricular dysfunction and prolonged ventilator support were associated with hypothyroidism. We reviewed the available literature on the effect of thyroid hormone supplementation in paediatric patients undergoing open-heart surgery under cardiopulmonary bypass and concluded that children after complex congenital cardiac surgery are at risk of developing a clinically significant hypothyroid state in the early postoperative period. In the literature where the effects of supplementation of thyroxine were studied, beneficial effects were observed in terms of reduced mechanical ventilation time, reduced inotropic support and intensive care unit stay, rapid achievement of negative fluid balance and early recovery. Supplementation with thyroid hormones enables a smoother postoperative recovery and is beneficial. The total duration of this therapy is, however, unclear.

Maternal hypothyroxinaemia in pregnancy is associated with obesity and adverse maternal metabolic parameters.

ObjectiveSubclinical hypothyroidism and isolated hypothyroxinaemia in pregnancy have been associated with an increased risk of gestational diabetes. We aimed to ascertain if these women have a worse metabolic phenotype than euthyroid pregnant women.Design, subjects and methodsWe recruited 956 healthy Caucasian women with singleton, non-diabetic pregnancies from routine antenatal clinics. Detailed anthropometric measurements (including BMI and skinfold thickness) and fasting blood samples (for TSH, free thyroxine (FT4), free triiodothyronine (FT3), HbA1c, lipid profile, plasma glucose and insulin resistance (HOMA-IR) analysis) were obtained at 28 weeks gestation.ResultsIn comparison to euthyroid women (n=741), women with isolated hypothyroxinaemia (n=82) had significantly increased BMI (29.5 vs 27.5 kg/m2, P<0.001), sum of skinfolds (57.5 vs 51.3 mm, P=0.002), fasting plasma glucose (4.5 vs 4.3 mmol/l, P=0.01), triglycerides (2.3 vs 2.0 mmol/l, P<0.001) and HOMA-IR (2.0 vs 1.3, P=0.001). Metabolic parameters in women with subclinical hypothyroidism (n=133) were similar to those in euthyroid women. Maternal FT4 was negatively associated with BMI (r=−0.22), HbA1c (r=−0.14), triglycerides (r=−0.17), HOMA-IR (r=−0.15) but not total/HDL cholesterol ratio (r=−0.03). Maternal FT3:FT4 ratio was positively associated with BMI (r=0.4), HbA1c (r=0.21), triglycerides (r=0.2), HOMA–IR (r=0.33) and total/HDL cholesterol ratio (r=0.07). TSH was not associated with the metabolic parameters assessed.ConclusionsIsolated hypothyroxinaemia, but not subclinical hypothyroidism, is associated with adverse metabolic phenotype in pregnancy, as is decreasing maternal FT4 and increasing FT3:FT4 ratio. These associations may be a reflection of changes in the thyroid hormone levels secondary to increase in BMI rather than changes in thyroid hormone levels affecting body weight and related metabolic parameters.

Subclinical hypothyroidism and its relation to obesity in patients before and after Roux-en-Y gastric bypass

BackgroundSubclinical hypothyroidism (SH), defined as a raised serum thyroid-stimulating hormone (TSH) with a normal free thyroxine (FT4), is occasionally observed in morbidly obese patients. ObjectivesIt is currently not known whether thyroid hormone treatment is indicated. The aim of the present study was to assess the changes in thyroid hormone levels in thyroxine-naïve patients with SH in response to weight loss induced by Roux-en-Y gastric bypass (RYGB). SettingGeneral hospital specialized in bariatric surgery. MethodsSerum levels of TSH and FT4 were measured at baseline in 503 patients presenting for RYGB. In patients diagnosed with SH, these measurements were repeated 12 months postoperatively. ResultsSH de novo was present in 71 out of 503 patients (14.1%). One-year follow-up was available in 61 out of 71 patients (86%). TSH level>10 mU/L was observed in 3 patients (.5%). RYGB induced a decrease in BMI from 47±8 kg/m2 to 33±6 kg/m2 at 12-month follow-up (P<.001), and this was associated with a decrease in TSH from 5.8±2.0 to 2.8±1.3 mU/L (P<.001) and a decrease in FT4 from 15.2±2.1 to 13.9±2.3 pmol/L (P<.001), respectively. SH completely resolved in 53 (87%) of the de novo cases. ConclusionThe prevalence of SH de novo is high in morbidly obese patients. After RYGB it resolves in about 90% of patients. This high degree of spontaneous recovery suggests that follow-up alone is sufficient in the majority of patients.

Whether the administration of thyroid hormones may play a role in the treatment of short stature?

Normal thyroid hormone secretion or optimal substitution of L-thyroxine is necessary for the proper functioning of the hypothalamic-pituitary-IGF-I axis. Over 30 years ago Cacciari et al. [1] indicated a slight risk of inducing an alteration of thyroid function in patients with GH deficiency during hGH therapy and recovery of thyroxine (T4) and trijodthyronine (T3) values to normal limits during follow-up. The rGH therapy might disclose previously unrecognised thyroid insufficiency rather than induce hypothyroidism [2,3]. The phenomenon of unmasking central hypothyroidism after the beginning of rGH therapy in some children with previous diagnosis of isolated GH-deficiency was described. Changes in TSH secretion during initial phase of the rGH therapy are less evident than fluctuations of FT4 concentration. The possibility of a decrease of TSH in terms of rhGH administration has been explained by an increase of somatostatin, a natural TSH inhibitor. The most frequently quoted mechanism of changes in thyroid hormone levels is GH-mediated increase of peripheral T4 to T3 deiodination. The potential role of IGF-I in stimulating that process has been postulated. Chernausek et al. [4] documented that IGF-I concentrations were diminished in hypothyroid patients. The mechanism of this phenomenon remained unclear. Diminished GH secretion or direct effects of hypothyroidism upon IGF-I production were considered. It is well documented that in patients with congenital hypothyroidism and caused by thyroiditis L-T4 replacement led to physiological increase of IGF-I and IGFBP3 secretion. It was proven that in children with neglected congenital hypothyroidism, even after a long period of hypothyroidism, L-T4 replacement improved the growth rate, leading to a partial recovery of the GH-IGF-I axis [5]. In GH-deficient children from the beginning of rhGH therapy - in euthyroid status - has not been recommended the obligatory L-T4 supplementation due a little evidence for the development of clinically significant hypothyroidism in most of previously euthyroid patients and spontaneous recovery to pre-treatment thyroid function in most patients [6]. Maintaining euthyroid status is important for the best effectiveness of rhGH therapy. The incidence of revealing hypothyroidism should be taken into account while starting rhGH therapy, as hypothyroidism may worsen the poor response to the therapy. It seems that assessment of TSH and FT4 concentration after rhGH therapy onset should be performed earlier and more often - for example every 3 months. It seems important to establish, if possible, the threshold values of pre-rhGH treatment TSH and/or FT4 levels for revealing hypothyroidism during rhGH therapy [7].

A case of masked toxic adenoma in a patient with non-thyroidal illness

BackgroundNon-thyroidal illness (NTI) refers to changes in thyroid hormone levels in critically ill patients in the absence of primary hypothalamic-pituitary-thyroid dysfunction, and these abnormalities usually resolve after clinical recovery. However, NTI can be accompanied by primary thyroid dysfunction. We report herein a case of a woman with NTI accompanied by primary hyperthyroidism.Case presentationA 52-year-old female was admitted to the intensive care unit with heart failure and atrial fibrillation. She had a longstanding thyroid nodule, and a thyroid function test revealed low levels of triiodothyronine and free thyroxine as well as undetectable thyroid stimulating hormone (TSH). She was diagnosed with NTI, and her TSH level began to recover but not completely at discharge. The thyroid function test was repeated after 42 months to reveal primary hyperthyroidism, and a thyroid scan confirmed a toxic nodule.ConclusionThis case suggests that although NTI was diagnosed, primary hyperthyroidism should be considered as another possible diagnosis if TSH is undetectable. Thyroid function tests should be repeated after clinical recovery from acute illness.

Visual pigments and opsin expression in the juveniles of three species of fish (rainbow trout, zebrafish, and killifish) following prolonged exposure to thyroid hormone or retinoic acid

Thyroid hormone (TH) and retinoic acid (RA) are powerful modulators of photoreceptor differentiation during vertebrate retinal development. In the embryos and young juveniles of salmonid fishes and rodents, TH induces switches in opsin expression within individual cones, a phenomenon that also occurs in adult rodents following prolonged (12 week) hypothyroidism. Whether changes in TH levels also modulate opsin expression in the differentiated retina of fish is unknown. Like TH, RA is essential for retinal development, but its role in inducing opsin switches, if any, has not been studied. Here we investigate the action of TH and RA on single-cone opsin expression in juvenile rainbow trout, zebrafish, and killifish and on the absorbance of visual pigments in rainbow trout and zebrafish. Prolonged TH exposure increased the wavelength of maximum absorbance (λmax ) of the rod and the medium (M, green) and long (L, red) wavelength visual pigments in all fish species examined. However, unlike the opsin switch that occurred following TH exposure in the single cones of small juvenile rainbow trout (alevin), opsin expression in large juvenile rainbow trout (smolt), zebrafish, or killifish remained unchanged. RA did not induce any opsin switches or change the visual pigment absorbance of photoreceptors. Neither ligand altered cone photoreceptor densities. We conclude that RA has no effect on opsin expression or visual pigment properties in the differentiated retina of these fishes. In contrast, TH affected both single-cone opsin expression and visual pigment absorbance in the rainbow trout alevin but only visual pigment absorbance in the smolt and in zebrafish. The latter results could be explained by a combination of opsin switches and chromophore shifts from vitamin A1 to vitamin A2.

Age-related changes in Thyroid hormone levels of bonobos and chimpanzees indicate heterochrony in development

We present information on age related changes of thyroid hormone levels in bonobos (N = 96) and chimpanzees (N = 100) ranging between one and 56 years of age. Fresh urine samples were used for hormone measurements with a commercial competitive total triiodothyronine (T3) ELISA. In both species, immature individuals had higher TT3 levels than adults and there was a marked decrease in TT3 levels between age classes. The two species differed in terms of the timing of TT3 level changes, with chimpanzees experiencing a significant decline in TT3 levels after 10 years of age and bonobos after 20 years of age. The decline of TT3 in chimpanzees appears to coincide with the time when somatic growth terminates while TT3 values in bonobos decrease much later. This temporal asymmetry in urinary thyroid hormone levels indicates heterochrony in the ontogenetic changes of the two sister species and developmental delay in bonobos. The prolongation of high TT3 levels in bonobos, which is characteristic of immatures of both Pan species may affect the behavior of bonobos; namely, the low intensity of aggression they display. Given that developmental studies are often based on post-mortem analyses of skeletons, measures of urinary thyroid hormones offer a non-invasive tool for exploring ontogenetic changes in living wild and captive hominoids.

Seasonal and socioeconomic influences on thyroid function among the Yakut (Sakha) of Eastern Siberia

Previous research has shown that the extreme cold and short day lengths of polar winters promote increased production and uptake of thyroid hormones, resulting in marked declines in free triiodothyronine (fT3). However, this "polar T3 syndrome" has been documented almost exclusively on small samples of male sojourners and little is known about seasonal changes in thyroid function among indigenous circumpolar groups. The present study addresses this gap by examining seasonal changes in thyroid hormone levels among the indigenous Yakut (Sakha) of northeastern Siberia. Anthropometric dimensions and thyroid measures (fT3, free thyroxine [fT4], thyroid-stimulating hormone [TSH]) were obtained on two occasions (July/August, 2009 and January 2011) on a sample of 134 Yakut adults (51 men, 83 women) from the village of Berdygestiakh, Sakha Republic/Yakutia, Russia. Yakut men and women both displayed significant declines in fT3 and fT4, and significant increases in TSH from summer to winter despite showing only modest seasonal changes in body mass and composition. Among men, gains in fat-free mass (FFM) were associated with larger reductions in fT3 and greater increases in TSH. Men living more traditional lifeways showed larger winter declines in fT4 and greater increases in TSH. The Yakut exhibited significant winter declines in fT3 levels similar to other circumpolar groups studied. However, the magnitude of seasonal change was greater in the Yakut, perhaps reflecting their distinctive metabolic physiology. Lifestyle factors play a mediating role in thyroid responses, such that men with more traditional lifeways had more exaggerated seasonal changes.

Effect of ascorbic acid on long-term cold exposure induced changes in thyroid activity in Sprague Dawley rats.

To determine the effect of ascorbic acid supplementation on long-term cold exposure induced changes in thyroid activity in Sprague-Dawley rats. Experimental study. Physiology Department of Islamic International Medical College, Rawalpindi, National Institute of Health, Islamabad and Railway Hospital, Rawalpindi, from January to December 2009. Ninety Sprague-Dawley rats were randomly divided into three groups of control, cold exposed and cold exposed along with ascorbic acid supplementation. After one month, their thyroid levels were analyzed by using chemiluminescent immunometric assay on Siemens Immulite 2000 Analyzer. After 4 weeks of cold exposure to experimental animals, the thyroid activity was raised significantly in the cold exposed group as compared to the control group (p-value for T3 difference = 0.004, T4 difference = 0.002 and TSH difference < 0.001). Supplementation with ascorbic acid in the third group normalized the thyroid hormone activity with p-value for difference in levels of T3 being 0.6661, T4 = 0.027 and TSH = 0.0028. Ascorbic acid prevented the cold induced changes in thyroid hormone levels in rodents.

Effect of N-acetylcysteine on serum thyroid hormone levels in nonthyroidal illness syndrome

Nonthyroidal illness syndrome (NTIS) refers to changes in thyroid hormone levels affecting up to 75% of critically ill patients. Cytokines and oxidative stress have been implicated as causative factors, as they derange deiodinase reactions. Interestingly, the addition of N-acetylcysteine (NAC) in a cell model prevented the effect of IL-6 on deiodinases, probably through a mechanism that restores catalytic activity of the enzyme [1]. NTIS is an independent marker of poor prognosis during myocardial infarction (MI) [2]. Here, we investigate whether NAC administration would prevent the decrease in serum thyroid hormone levels observed in patients with MI.

Acute psychosis caused by hypothyroidism following radioactive iodine treatment of Graves’ disease

This case serves as a poignant reminder that sudden changes in thyroid hormone levels (e.g. acute hypothyroidism) can induce psychosis.

Minimal changes of thyroid axis activity influence brain functions in young

There is evidence of an association between thyroid hormones (TH) alterations and mental dysfunctions related to procedural and working memory functions, but the physiological link between these domains is still under debate, also for the presence of age as a confounding factor. Thus, we investigated the TH tuning of cerebral functions in young females affected by the borderline condition of subclinical hypothyroidism (SH) and in euthyroid females of the same age. The experiment consisted in the characterization of the affective state and cognitive abilities of the subjects by means of specific neuropsychological questionnaires, and of brain activity (EEG) in resting state and during the passive viewing of emotional video-clips. We found that SH had i) increased anxiety for Physical Danger; ii) better scores for both Mental Control and no-working-memory-related functions; iii) association between anxiety for Physical Danger and fT4 levels. Thus, in young adults, SH increases inward attention and paradoxically improves some cognitive functions. In addition, self-assessed questionnaires showed that SH had a greater susceptibility to unpleasant emotional stimulation. As for EEG data, SH compared to controls showed: i) reduction of alpha activity and of gamma left lateralization in resting state; ii) increased, and lateralized to the right, beta2 activity during stimulations. Both results indicated that SH have higher levels of arousal and greater susceptibility to negative emotion than controls. In conclusion, our study indicates that minimal changes in TH levels produce subtle but well-defined mental changes, thus encouraging further studies for the prediction of pathology evolution.

The role of thyroid hormones as inductors of oxidative stress and neurodegeneration.

Reactive oxygen species (ROS) are oxidizing agents amply implicated in tissue damage. ROS production is inevitably linked to ATP synthesis in most cells, and the rate of production is related to the rate of cell respiration. Multiple antioxidant mechanisms limit ROS dispersion and interaction with cell components, but, when the balance between ROS production and scavenging is lost, oxidative damage develops. Many traits of aging are related to oxidative damage by ROS, including neurodegenerative diseases. Thyroid hormones (THs) are a major factor controlling metabolic and respiratory rates in virtually all cell types in mammals. The general metabolic effect of THs is a relative acceleration of the basal metabolism that includes an increase of the rate of both catabolic and anabolic reactions. THs are related to oxidative stress not only by their stimulation of metabolism but also by their effects on antioxidant mechanisms. Thyroid dysfunction increases with age, so changes in THs levels in the elderly could be a factor affecting the development of neurodegenerative diseases. However, the relationship is not always clear. In this review, we analyze the participation of thyroid hormones on ROS production and oxidative stress, and the way the changes in thyroid status in aging are involved in neurodegenerative diseases.

Lake Tana large barbs diversity: Developmental and hormonal bases

Helerochronies caused by changes in the hormonal status are proposed to play a major role in the diversification of the Lake Tana barbs of Labeobarbus (=Barbus) genus (Dgebuadze and Mina, 2008). To test this hypothesis, we (i) compared temporal patterns of cranial development in L. intermedius, likely ancestral for Tana species flock, and L. brevicephalus and L. megastoma proposed to be paedomoiphic and peramoiphic, respectively; (ii) studied the role of thyroid hormone (TH) in the regulation of L. intermedius development; (iii) evaluated the effect of TH changes on the definitive morphology, and (iv) evaluated the possible role of TH in diversification of Tana barbs. Skull development was found to be heterochronicaily changed in L. brevicephalus and L. megastoma as compared to L. intermedius; revealed heteroclironies may account for differences in skull proportions distinguishing these barbs, TH was shown to play a major role in the regulation of ontogeny. Changes in TH level cause heterochronies in the development of a skull, axial skeleton, fins and fin girdles, squamation, and dentition. Heteroclironies were shown to influence adult morphology of these structures. These findings support the hypothesis of the involvement of developmental and hormonal factors in the diversification of the Lake Tana large barbs.

Determination of serum neopterin levels in patients with autoimmune thyroid diseases

An elevated serum level of neopterin indicates the activation of the cellular immune system. The objective was to find a correlation in autoimmune thyroid patients between neopterin levels and the clinical stage of the disease and to examine whether neopterin can predict the relapse of the disease. Serum neopterin, thyroid stimulating hormone, free thyroxine, free triiodothyronine, anti-thyroglobulin and anti-thyroid peroxidase antibody levels were determined in 137 patients with Graves' disease (in different stages), 25 with Hashimoto's thyroiditis and 14 with toxic adenoma. The neopterin levels were significantly higher in patients with Graves' disease (hyper-, eu-, hypothyroidism and relapsed hyperthyroidism) and Hashimoto's thyroiditis. Positive correlation was found between neopterin and anti-thyroglobulin and anti-thyroid peroxidase antibody levels, but no correlation was detected between neopterin levels and thyroid hormones, thyroid stimulating hormone values and antibodies against thyroid stimulating hormone receptors. Higher level of serum neopterin reflects an underlying autoimmune process, and does not correlate with changes in thyroid hormone levels. Determination of neopterin level can be an important indicator in the exacerbation of autoimmune processes.

Biomarkers of perchlorate exposure are correlated with circulating thyroid hormone levels in the 2007–2008 NHANES

Previous epidemiological studies provide conflicting evidence as to whether environmental perchlorate exposure can affect levels of circulating thyroid hormones in the general population. We investigated the statistical relationships between biomarkers of perchlorate exposure and serum thyroid hormone levels in 2007–2008 National Health and Nutrition Evaluation Survey (NHANES) subjects. Generalized additive mixed models (GAMMs) were developed to estimate the relationships between T3 and T4 levels and creatinine-adjusted urinary perchlorate excretion. The models included covariates related to gender, age, ethnicity, income, smoking status, prescription medications, and biomarkers of exposures to other goitrogenic ions and phthalate ester metabolites. Where necessary, relationships between hormone levels and covariates were represented as nonlinear smoothed terms. The effect of the hypothalamic–pituitary–thyroid (HPT) axis on serum hormone levels was taken into account by including a term for thyroid stimulating hormone (TSH) in the models. Regression coefficients for perchlorate were significant and negative in GAMMs predicting total T4 and free T3 levels in males, females, and for the entire cohort when phthalate ester biomarkers and other covariates were included. Coefficients for perchlorate were also significant and negative in regressions predicting free T4 levels in males and in the entire study population. The consistency of these results suggests that HPT axis controls do not completely compensate for small changes in thyroid hormone levels associated with perchlorate and phthalate ester exposures.

Benefits of vasodilating beta-adrenoblockers for arterial hypertension treatment

Antihypertensive medications of the same class could differ by their pharmacodynamic parameters, which substantially affects the longterm treatment results. Nebivolol is one of the modern, highly selective β-adrenoblockers (β-AB). It is characterised not only by high β1-selectivity, but also by additional vasodilating activity, due to increased nitric oxide synthesis and, hence, beneficial metabolic effects. The results of the original studies and the external evidence demonstrate metabolic neutrality of nebivolol, absence of substantial changes in thyroid hormone levels, and improvement in heart rate variability, electrophysiological myocardial parameters, QT interval duration, and cerebral perfusion. Nebivolol is effective and safe even in higher-risk patients with metabolic syndrome and Type 2 diabetes mellitus.