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Oestrogen exposure and breast cancer risk
Ruth C Travis, Timothy J Key
Breast Cancer Research , 2003, DOI: 10.1186/bcr628
Abstract: Epidemiological and experimental evidence implicates oestrogens in the aetiology of breast cancer. Most established risk factors for breast cancer in humans are thought to influence risk through hormone-related pathways [1], increased concentrations of endogenous oestrogens are strongly associated with increased risk for breast cancer in postmenopausal women [2], and trials have shown that the anti-oestrogens tamoxifen and raloxifene reduce the incidence of breast cancer [3]. Furthermore, experimental studies in animals have shown that oestrogens can promote mammary tumours, and a decrease in exposure to oestrogens, by performing an oophorectomy or giving an anti-oestrogenic drug, has the reverse effect [4]. However, the effects of oestrogen alone do not fully account for the relationships observed between breast cancer and hormone-related risk factors. Other hormones, such as progesterone [1], prolactin [5] and testosterone [6], may also be important.This article explores the evidence for the hypothesis that exposure to oestrogen is a major determinant of risk for breast cancer. It is not intended to be a comprehensive review but rather focuses on recent epidemiological and experimental data relating to the role of oestrogen in the aetiology of breast cancer and possible mechanisms that might account for the association. There are several forms of oestrogen, the principal form in humans being oestradiol, but for convenience in this article we refer generally to oestrogens except where it is necessary to be more specific.Oestrogens have an essential role, together with other hormones, in the development of the female sex organs and secondary sex characteristics, the regulation of the menstrual cycle and reproduction. Thus, it has been proposed that the effects of many established reproductive risk factors for breast cancer are mediated by hormonal mechanisms, for the most part involving oestrogens [1].Although risk for breast cancer increases with age, there is a ma
The many faces of testosterone
Jerald Bain
Clinical Interventions in Aging , 2007,
Abstract: Jerald BainDepartment of Medicine, Department of Obstetrics and Gynecology, University of Toronto, Ontario, Canada; Division of Endocrinology and Metabolism, Mount Sinai Hospital, Toronto, Ontario, CanadaAbstract: Testosterone is more than a “male sex hormone”. It is an important contributor to the robust metabolic functioning of multiple bodily systems. The abuse of anabolic steroids by athletes over the years has been one of the major detractors from the investigation and treatment of clinical states that could be caused by or related to male hypogonadism. The unwarranted fear that testosterone therapy would induce prostate cancer has also deterred physicians form pursuing more aggressively the possibility of hypogonadism in symptomatic male patients. In addition to these two mythologies, many physicians believe that testosterone is bad for the male heart. The classical anabolic agents, 17-alkylated steroids, are, indeed, potentially harmful to the liver, to insulin action to lipid metabolism. These substances, however, are not testosterone, which has none of these adverse effects. The current evidence, in fact, strongly suggests that testosterone may be cardioprotective. There is virtually no evidence to implicate testosterone as a cause of prostate cancer. It may exacerbate an existing prostate cancer, although the evidence is flimsy, but it does not likely cause the cancer in the first place. Testosterone has stimulatory effects on bones, muscles, erythropoietin, libido, mood and cognition centres in the brain, penile erection. It is reduced in metabolic syndrome and diabetes and therapy with testosterone in these conditions may provide amelioration by lowering LDL cholesterol, blood sugar, glycated hemoglobin and insulin resistance. The best measure is bio-available testosterone which is the fraction of testosterone not bound to sex hormone binding globulin. Several forms of testosterone administration are available making compliance much less of an issue with testosterone replacement therapy.Keywords: testosterone, androgens, male hypogonadism, anabolic steroids
Multiple Routes to Oestrogen Antagonism  [PDF]
Hilary R. Glover,Stewart Barker,Sylvanie D. M. Malouitre,John R. Puddefoot,Gavin P. Vinson
Pharmaceuticals , 2010, DOI: 10.3390/ph3113417
Abstract: Several lines of evidence attest to the existence of alternative ligand binding sites on the oestrogen receptor (ER), including non-competitive inhibition by trilostane or tamoxifen. It is possible that the inhibitory action of conventional oestrogen agonists at high concentrations may indicate that they too interact at alternative ER sites, albeit at low affinity. To test this possibility an oestrogen reporter assay was used to compare the activity of different oestrogens and antagonists in breast cancer and prostate cell lines. All four cell lines tested contained different amounts of oestrogen receptor α (ERα), ERβ, progesterone receptor and coregulator mRNA. Though differences were observed in response to stimulation and inhibition, these correlated only with the presence or absence of ERα, and not with the other components. Thus stimulation of the reporter by oestradiol and oestrone was biphasic in the breast cancer cells, while prostate cells were unable to respond. Only T47D cells were stimulated by oestriol or diethylstilboestrol, however reporter activity of all the cell lines was repressed by 10mM diethylstilboestrol. Reporter activity of MCF-7 cells was inhibited by tamoxifen, raloxifene and ICI 182,780, but stimulated by trilostane, yet all these antioestrogens inhibited agonist-stimulated activity. Trilostane also inhibited the agonism seen in cells co-treated with E2 and tamoxifen. It is clear that several of the compounds tested may have either agonist or antagonist effects under different conditions and at different concentrations, acting through ERα alone. Though biphasic dose response curves, or hormesis, have been attributed to various mechanisms, we here provide evidence that alternative ligand binding sites may contribute to this phenomenon.
Santa and the moon  [PDF]
Peter Barthel
Physics , 2011,
Abstract: Happy end-of-the-year evening and night events provide good opportunities to explain the phases of the moon. The need for such moon phase education is once again demonstrated, through an investigation of illustrations on Santa Claus and Christmas gift wrap and in children's books, in two countries which have been important in shaping the image of Santa Claus and his predecessor Sinterklaas: The Netherlands and the USA. The moon on Halloween illustrations is also considered. The lack of knowledge concerning the physical origin of the moon phases, or lack of interest in understanding, is found to be widespread in The Netherlands but is also clearly present in the USA, and is quite possibly global. Definitely incomplete, but surely representative lists compiling both scientifically correct and scientifically incorrect gift wrap and children's books are also presented.
Testosterone and Depression  [PDF]
?ükrü Kartalc?
Psikiyatride Guncel Yaklasimlar , 2010,
Abstract: Androgens have various effects on human body and mood. Testosterone, a hormone mainly secreted from testes and adrenals, is one of the most potent androgens. Multiple studies have found that testosterone plays a role in regulating sexual activity, libido, social behaviors, aggression, cognitive functions, sleep control and well-being in men and women. Testosterone deficiency in hypogonadic or elderly men leads to neuropsychiatric problems, such as fatigue, loss of libido, irritability, insomnia and depressive mood. Testosterone replacement therapy consistently reverses these sequel in men. On the other hand, hyperandrogenic states in women are related to aggression and antisocial behavior, which might lead to depressive mood. Low testosterone levels may also result in depression among oophorectomized women. Because of such effects, a relationship between testosterone and depression has long been an issue of speculation, but yet very few studies have addressed this relation. Along with clinical studies, experimental and epidemiological studies show that testosterone is related to depression in men and women. But studies of testosterone concentrations in depression have yielded inconsistent results reporting low as well as high testosterone levels associated with depression. In this article, the physiological and psychological effects of testosterone and evidence regarding its relationship to depressive disorders and possible gender differences have been reviewed.
The Tethered Moon  [PDF]
Kevin J. Zahnle,Roxana Lupu,Anthony Dobrovolskis,Norman H. Sleep
Physics , 2015, DOI: 10.1016/j.epsl.2015.06.058
Abstract: We address the thermal history of the Earth after the Moon-forming impact, taking tidal heating and thermal blanketing by the atmosphere into account. The atmosphere sets an upper bound of ~100 W/m^2 on how quickly the Earth can cool. The liquid magma ocean cools over 2-10 Myrs, with longer times corresponding to high angular-momentum events. Tidal heating is focused mostly in mantle materials that are just beginning to freeze. The atmosphere's control over cooling sets up a negative feedback between viscosity-dependent tidal heating and temperature-dependent viscosity of the magma ocean. While the feedback holds, evolution of the Moon's orbit is limited by the modest radiative cooling rate of Earth's atmosphere. Orbital evolution is orders of magnitude slower than in conventional constant Q models, which promotes capture by resonances. The evection resonance is encountered early, when the Earth is molten. Capture by the evection resonance appears certain but unlikely to generate much eccentricity because it is encountered early when the Earth is molten and Q_Earth >> Q_Moon. Tidal dissipation in the Earth becomes more efficient (Q_Earth << Q_Moon) later when the Moon is between ~20 R_Earth and ~40 R_Earth. If lunar eccentricity grew great, this was when it did so, perhaps setting the table for some other process to leave its mark on the inclination of the Moon.
Micro moon versus macro moon: Brightness and size  [PDF]
Dulli Chandra Agrawal
Physics , 2015,
Abstract: The moon, moonlight, phases of the moon and its relatively simple recurring cycle has been of interest since time immemorial to the human beings, navigators, astronomers and astrologers. The fact that its orbit is elliptical as well its plane is inclined with the plane of rotation of the earth gives rise to new moon to full moon and solar and lunar eclipses. During the phase of the full moon, the luminous flux and its apparent size will depend on its distance from the earth. In case it is at farthest point known as lunar apogee causes smallest full moon or micro full moon and if it is closest to us termed as lunar perigee will result in macro full moon, also known as super moon, a term coined by astrologer Richard Nolle in 1979. The theoretical expressions for the lunar luminous fluxes on the earth representing the power of lunar light the earth intercepts in the direction normal to the incidence over an area of one square meter are derived for two extreme positions lunar apogee and lunar perigee. The expressions for the apparent sizes of full moons corresponding to said positions are also mentioned. It is found that full perigee moon is about 29 percent brighter and 14 percent bigger than the full apogee moon consistent with the reported values.
Moon Shadow Observation by IceCube  [PDF]
D. J. Boersma,L. Gladstone,A. Karle,for the IceCube Collaboration
Physics , 2010,
Abstract: In the absence of an astrophysical standard candle, IceCube can study the deficit of cosmic rays from the direction of the Moon. The observation of this "Moon shadow" in the downgoing muon flux is an experimental verification of the absolute pointing accuracy and the angular resolution of the detector with respect to energetic muons passing through. The Moon shadow has been observed in the 40-string configuration of IceCube. This is the first stage of IceCube in which a Moon shadow analysis has been successful. Method, results, and some systematic error studies will be discussed.
Einstein's Moon  [PDF]
D. Song
Physics , 2010,
Abstract: An account of the subjective elements of quantum mechanics or of whether, as Einstein famously asked, the Moon exists when nobody is looking at it.
Relativistic Effects in the Motion of the Moon  [PDF]
Bahram Mashhoon,Dietmar S. Theiss
Physics , 2000,
Abstract: The main general relativistic effects in the motion of the Moon are briefly reviewed. The possibility of detection of the solar gravitomagnetic contributions to the mean motions of the lunar node and perigee is discussed.
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