24,274 research outputs found

    A case-control study of drug risk factors for age-related macular degeneration.

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    OBJECTIVE: To investigate the association between age-related macular degeneration (AMD) and exposure to antacids, antithyroids, thyroid hormones, and thiazide diuretics. DESIGN: Matched case-control study. PARTICIPANTS: Population-based participants were selected from the United Kingdom General Practice Research Database. A total of 18,007 people with diagnosed AMD were compared with 86 169 controls matched for age, gender, and general practice. METHODS: Conditional logistic regression was used to determine the association between exposure to each drug group of interest and a diagnosis of AMD, adjusting for relevant confounding variables. MAIN OUTCOME MEASURES: The primary outcome was the odds ratio for the association between exposure to antacids, antithyroids, thyroid hormones, or thiazide diuretics and AMD. Secondary analyses were conducted to assess the effect of recent exposure to the drugs of interest, the total number of prescriptions received, and restricting the data set to participants with more than 2 years of observation time. RESULTS: The crude odds ratios for association between any record of drug exposure and AMD were as follows: 1.34 (95% confidence interval [CI], 1.29-1.39) for antacids; 1.15 (95% CI, 0.92-1.44) for antithyroids; 1.34 (95% CI, 1.29-1.39) for thyroid hormones; and 1.13 (95% CI, 1.08-1.17) for thiazide diuretics. After adjusting for consultation rate, observation time, diabetes, heart failure, hyperlipidemia, cardiovascular drug use, atherosclerosis, hypertension, aspirin use, hormone replacement therapy use, body mass index, alcohol consumption, and smoking, the odds ratios reduced to: 1.06 (95% CI, 1.02-1.10) for antacids, 0.98 (95% CI, 0.78-1.24) for antithyroids, 0.99 (95% CI, 0.92-1.06) for thyroid hormones, and 0.98 (95% CI, 0.94-1.02) for thiazides. Secondary analyses were consistent with these findings for all 4 drug categories. CONCLUSIONS: No association was detected between short- and medium-term use of antithyroids, thyroid hormones, and thiazide diuretics and the risk of AMD. Short- and medium-term use of antacids seems to be associated with a small increase in the risk of this disease. However, this increased risk is likely the result of residual confounding by smoking or uncontrolled confounding resulting from socioeconomic status. No conclusions could be drawn regarding longer-term use of each drug category

    Imbalance between thyroid hormones and the dopaminergic system might be central to the pathophysiology of restless legs syndrome: a hypothesis

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    Data collected from medical literature indicate that dopaminergic agonists alleviate Restless Legs Syndrome symptoms while dopaminergic agonists antagonists aggravate them. Dopaminergic agonists is a physiological regulator of thyroid-stimulating hormone. Dopaminergic agonists infusion diminishes the levels of thyroid hormones, which have the ability to provoke restlessness, hyperkinetic states, tremors, and insomnia. Conditions associated with higher levels of thyroid hormones, such as pregnancy or hyperthyroidism, have a higher prevalence of Restless Legs Syndrome symptoms. Low iron levels can cause secondary Restless Legs Syndrome or aggravate symptoms of primary disease as well as diminish enzymatic activities that are involved in dopaminergic agonists production and the degradation of thyroid hormones. Moreover, as a result of low iron levels, dopaminergic agonists diminishes and thyroid hormones increase. Iron therapy improves Restless Legs Syndrome symptoms in iron deprived patients. Medical hypothesis. To discuss the theory that thyroid hormones, when not counterbalanced by dopaminergic agonists, may precipitate the signs and symptoms underpinning Restless Legs Syndrome. The main cause of Restless Legs Syndrome might be an imbalance between the dopaminergic agonists system and thyroid hormones

    The potential usage of thyroid hormones as sport doping - a mini-review

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    A thyroid gland is one of the most important organs of a human body. Thyroid hormones, at least in physiological concentration, have anabolic features. The aid of this review is to summarize knowledge on potential usage of thyroid hormones in sport doping.             Thyroid hormones play a crucial role in skeletal muscles physiology. The exposition to T3 and T4 may improve myogenesis, muscles regeneration and muscles blood blow. In a long-time perspective, those hormones may help in reducing body weight.             According to those mechanisms, thyroid hormones may be considered as a plausible agent in sport doping. However WADA guidelines does not include T3 or T4 in a list o sport doping substances, the debate on their inclusion is on-going, and the physicians should be aware of thyroid hormones effects on human metabolism from sports medicine perspective

    Revisiting thyroid hormones in schizophrenia

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    Thyroid hormones are crucial during development and in the adult brain. Of interest, fluctuations in the levels of thyroid hormones at various times during development and throughout life can impact on psychiatric disease manifestation and response to treatment. Here we review research on thyroid function assessment in schizophrenia, relating interrelations between the pituitary-thyroid axis and major neurosignaling systems involved in schizophrenia’s pathophysiology. These include the serotonergic, dopaminergic, glutamatergic, and GABAergic networks, as well as myelination and inflammatory processes. The available evidence supports that thyroid hormones deregulation is a common feature in schizophrenia and that the implications of thyroid hormones homeostasis in the fine-tuning of crucial brain networks warrants further research.The present work was supported by Grant POCI/SAUESP/58757/2004 from the Portuguese Science Foundation (FCT/FEDER). NCS was supported by the fellowship SFRH/ BPD/51057/2010 by FCT

    Perubahan Kadar Hormon Tiroid pada Penderita Sindroma Nefrotik

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    Thyroid hormones levels in nephrotic syndromeBackground: Nephrotic syndrome is one of the most found kidney disease. A great part (>99%) of circulating thyroid hormones were bound to proteins, thus derangements of blood proteins in nephrotic syndrome are potential to disturb thyroid hormones levels. This study was aimed to compare thyroid hormones levels changes in childhood Nephrotic Syndrome before and after remission.Method: Thirty four nephrotic syndrome patients studied on Department of pediatric of Dr. Kariadi Hospital, Semarang between April 1995 to June 1996 were for albumin, cholesterol, thyroid and thyroid stimulating hormone levels before and after remission and were tested with Wilcoxon signed rank test. The correlation between albumin and thyroxin levels before and after remission. were analyzed with Spearman correlation test.Results: T4 level before remission was 26.89±16.12 nmol/L, TSH 9.36±5.51 IU/ml, and after remission T4 106.63±28.02 nmol/L,TSH 1.78±1.91 μIU/mL. There were significant changes of thyroid hormones levels before and after remission (z=5.09; p=0.000). There were positive correlation between blood protein (albumin) level and thyroid hormone (T4) level in nephrotic syndrome before remission (r=0.51; p=0.000) and after remission (r=0.38; p=0.004). A great proportion of nephrotic syndrome patients, suffered from hypothyroidism and return to euthyroid after remission.Conclusions: Thyroid hormone levels changed during the course of nephrotic syndrome

    Involvement of the hypothalamic-pituitary-thyroid axis and its interaction with the hypothalamic-pituitary-adrenal axis in the ontogeny of avian thermoregulation: a review

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    The emergence of thermoregulation in avian species is a complex matter in which neural as well as hormonal processes are involved. In a previous paper, the neural aspects of primary avian thermoregulation were discussed. In this paper the role of the hypothalamus-pituitary-thyroid axis (HPT-axis) and the hypothalamus-pituitary-adrenal axis (HPA-axis) in the ontogeny of avian thermoregulation is evaluated. The regulatory mechanisms and different important hormones of both axes, which have stimulatory or inhibitory effects, are discussed. Because the onset of functionality of the thermoregulatory system is of great interest, the ontogeny and functionality of the hormonal axes are clarified. There is a great difference between precocial and altricial birds in hormonal events as well as in neural processes which are involved in the emergence of thermoregulation. In precocial avian species the HPT-axis becomes functional during the mid- to late embryonic period while the same axis only becomes fully functional during the first week post-hatch in altricial avian species. As early as the sixties, the emergence of homeothermy in chickens was investigated. It was concluded that the thyroid gland plays an important role in the thermoregulatory mechanisms of newly hatched chicks. More recent studies however were not able to show any direct effect of the thyroid hormones on the thermoregulation of day-old chicks, although blocking the conversion of T4 to T3 caused a decrease in body temperature in young chicks. Thyrotropin releasing hormone (TRH) is known to act in thermoregulation in mammals and several authors have found an effect of TRH on the metabolism of young and older chicks. However, the exact mechanism still remains unclear. Because the HPT- and the HPA-axis show close relationships, the role of the HPA-axis in the ontogeny of thermoregulation is also taken into consideration in this review. In mammals as well as in birds, corticotropin releasing hormone (CRH) is involved in the primary thermoregulation. We conclude that the HPT-axis has an important role in the ontogeny of avian thermoregulation. The exact role of the HPA-axis remains largely unclear although at least CRH is definitely of some importance

    Thyroid hormone status within the physiological range affects bone mass and density in healthy men at the age of peak bone mass

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    Context: The hormonal factors involved in the regulation of peak bone mass (PBM) in men have not been fully investigated. Apart from gonadal steroids and somatotropic hormones, thyroid hormones are known to affect bone maturation and homeostasis and are additional candidate determinants of adult bone mass. Objective: We aimed to investigate between-subject physiological variation in free and total thyroid hormone concentrations, TSH, and thyroid binding globulin (TBG) in relation to parameters of bone mass, geometry, and mineral density in healthy men at the age of PBM. Design and setting: We recruited 677 healthy male siblings aged 25-45 years in a cross-sectional, population-based study. Areal and volumetric bone parameters were determined using dual-energy x-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Total and free thyroid hormones, TBG, and TSH were determined using immunoassays. Results: Free and total thyroid hormone concentrations were inversely associated with bone mineral density (BMD) and bone mineral content (BMC) at the hip and total body (free triiodothyronine (FT(3)), total T(3) (TT(3)), and total T(4) (TT(4))) and at the spine (FT(3)). TBG was negatively associated with BMC and areal BMD at all sites. At the radius, cortical bone area was inversely associated with TT(3), TT(4), and TBG, and trabecular bone density was inversely associated with free thyroxine, TT(4), and TBG. We observed inverse associations between cortical bone area at the mid-tibia and FT(3), TT(3), TT(4), and TBG. No associations between TSH and DXA or pQCT measurements were found. Conclusion: In healthy men at the age of PBM, between-subject variation in thyroid hormone concentrations affects bone density, with higher levels of FT(3), TT(3), TT(4), and TBG being associated with less favorable bone density and content

    Variation in adrenal and thyroid hormones with life-history stage in juvenile northern elephant seals (Mirounga angustirostris)

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    Interpretation of stress responses in wildlife is inadequate due to the range of natural variation and potential confounds of individual and life-history variables. In marine mammals, endocrine response data are sparse and variable across species. Blood adrenal and thyroid hormones were measured in 144 chemically immobilized yearling elephant seals at Año Nuevo State Reserve to characterize variation between sexes and across semiannual haul-outs. There was no relationship between hormone concentration and time needed for collecting blood or diel pattern, suggesting that concentrations represented baseline values. Serum cortisol concentrations did not vary with gender or across fasts but increased dramatically during molting. Cortisol was significantly correlated with aldosterone at all measured life-history. Thyroxine levels were lower in females and decreased with fasting in both sexes during the Fall haul-out. Cortisol concentrations were correlated with reverse T3 concentrations across all measured life-history stages suggesting an important impact of cortisol on deiodinase enzymes and thyroid function. Significant variation in stress hormone concentrations with gender and life- history stage emphasizes the importance of contextual variables when interpreting serum hormone concentrations

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

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    Background: Triiodothyronine (T3) has many effects on the heart, and marked changes in cardiac function and structure occur in patients with (subclinical) thyroid disease. We investigated whether between-subject variation in thyroid hormone levels within the euthyroid range is also associated with heart rate and echocardiographic heart function and structure. Methods: Subjects were selected from the Asklepios study (n=2524), a population-representative random sample of patients aged between 35 and 55 years, free from overt cardiovascular disease at baseline. Analyses were restricted to 2078 subjects (1013 women and 1065 men), not using antihypertensive or thyroid medication nor having antithyroperoxidase antibody levels above clinical cut-off or thyrotropin (TSH) levels outside the reference range. All subjects were phenotyped in-depth and underwent comprehensive echocardiography, including diastolic evaluation. Thyroid function parameters were determined by automated electrochemiluminescence. Results: Heart rate was robustly positively associated with (quartiles of) free T3 (FT3) and T3, both in subjects with TSH levels within reference (0.27-4.2 μU/L) and in narrow TSH range (0.5-2.5 μU/L; p<0.0001). FT3 and T3 were negatively associated with left ventricular (LV) end-diastolic volume but positively associated with relative wall thickness. Total T3 (TT3) was associated with enhanced ventricular contraction (as assessed by tissue Doppler imaging). Free thyroxine, FT3, and TT3 were positively associated with late ventricular filling, and TT3 was associated with early ventricular filling. Conclusion: We have demonstrated a strong positive association between thyroid hormone levels within the euthyroid range and heart rate, and more subtle effects on cardiac function and structure. More specifically, we suggest a smaller LV cavity size (with increased relative wall thickness), an enhanced atrial and ventricular contraction, and LV relaxation with higher circulating thyroid hormones. These results illustrate that variation in thyroid hormone levels, even within the reference range, exerts effects on the heart

    Serum thyroxin level during the first-trimester of pregnancy

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    Objective: The aim of this study was to assess the requirement of serum thyroxin levels during the early stage of the first trimester of pregnancy. Methodology: Serum thyroxin levels of 120 apparently healthy women were evaluated in Gorgan in northern Iran during 2007-08 by the enzyme linked immunosorbant assay (ELISA). Results: According to the reference intervals of our standard kit, 48% of the pregnant women in this study had elevated thyroxin levels. Conclusion: The findings of this study can be misleading, because it was based on the laboratory standard kit, women normal range, as general. Pregnant women require higher levels of thyroxin and therefore, a specific normal range for the first trimester of pregnancy should be established in each particular region
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