Endocrine System, part 1 - Glands & Hormones: Crash Course A&P #23
Hypothalamus–Hypophysen–Nebennierenrinden–Achse (HPA-Achse): Ein ÜberblickDer Regelkreislauf zwischen Hypophyse, Hypothalamus und Neben nieren rinde hat mit der Ausschüttung von Glukokortikoiden eine zentrale Bedeutung in der Reaktion des menschlichen Körpers auf Stress. Dieses cascde konkret steroid hormone cascade chart Anstieg von Steroid hormone cascade chart und Katecholaminen z. Stress ist eine Reaktion des zentralen Nervensystems und wird im Wesentlichen über den Sympathikus und den endokrinologischen Weg über Hypothalamus, Hypophyse methyl 1 testosterone price letztendlich Nebennierenrinde vermittelt. Dieser Weg ist daher für die physiologische Stressantwort sehr relevant, hat aber auch darüber hinaus noch Interaktionen mit anderen Bereichen, beispielsweise mit dem Immunsystem oder dem Elektrolythaushalt. Der Hypothalamus ist die oberste Instanz und verbindet das Nervensystem mit dem endokrinen System.
Signaltransduktion und Hormone
Steroidhormone sind Steroide , die als Hormone wirken. Zu ihnen gehören die Sexualhormone der Keimdrüsen und die Corticosteroide der Nebennierenrinde. Die Steroidhormone der Säugetiere können in fünf Gruppen eingeteilt werden, nach den Steroidrezeptoren an denen sie binden: Glucocorticoide , Mineralocorticoide , Androgene , Estrogene und Gestagene.
Steroidhormone leiten sich vom Cholesterin ab und sind daher gut fettlöslich und schwer wasserlöslich. Dadurch können sie im Gegensatz zu den anderen Hormongruppen direkt in die Zelle gelangen und brauchen keinen Second Messenger.
Dort binden sie an ihre entsprechenden Rezeptoren und können so ihre Wirkung entfalten. Beim Transport über die Blutbahn sind Steroidhormone wegen ihrer wasserabweisenden Eigenschaften auf Plasmaproteine und spezielle Transportproteine angewiesen. Ausgehend vom Cholesterin entsteht Pregnenolon , das die zentrale Ausgangsverbindung der Steroidhormonbiosynthese ist. Cholesterin liefert das Sterangerüst , dem die Steroide ihren Namen verdanken.
Über drei verschiedene Wege entstehen aus Cholesterin die Mineralocorticoide , Glucocorticoide und Geschlechtshormone. Dies geschieht in der Nebennierenrinde und in den männlichen und weiblichen Gonaden Hoden und Eierstock.
Im Eierstock wird übrigens auch zunächst Testosteron also männliches Geschlechtshormon produziert, das dann mit einer Aromatase Enzym, das einen Kohlenstoffring aromatisch macht zu Estradiol umgebaut wird. Ihre Wirkungsdauer geht von einigen Stunden bis zu Tagen, wonach sie in der Leber wieder abgebaut werden. Die Enzyme, welche die einzelnen Schritte vom Cholesterin zu den Steroidhormonen katalysieren, können durch Gendefekte gestört sein.
Relativ häufig ist der Hydroxylase -Mangel. Dieser führt zu einer Überproduktion von Geschlechtshormonen, da der Weg zum Cortisol und Aldosteron gestört ist. Die Krankheit nennt sich Adrenogenitales Syndrom. Dabei gibt es sogenannte negative Rückkopplungsmechanismen, d. ACTH , wodurch das periphere Organ dann auch weniger synthetisiert. Steroidhormone werden auch als Arzneistoffe genutzt. Corticosteroide — Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones.
Some common naturally occurring steroid hormones are cortisol, corticosterone, cortisone and aldosterone, the main corticosteroids produced by the adrenal cortex are cortisol and aldosterone. Glucocorticoids such as cortisol affect carbohydrate, fat, and protein metabolism, and have anti-inflammatory, immunosuppressive, anti-proliferative, anti-inflammatory effects are mediated by blocking the action of inflammatory mediators and inducing anti-inflammatory mediators.
Immunosuppressive effects are mediated by suppressing delayed hypersensitivity reactions by direct action on T-lymphocytes, anti-proliferative effects are mediated by inhibition of DNA synthesis and epidermal cell turnover. Vasoconstrictive effects are mediated by inhibiting the action of inflammatory mediators such as histidine, synthetic pharmaceutical drugs with corticosteroid-like effects are used in a variety of conditions, ranging from brain tumors to skin diseases.
Dexamethasone and its derivatives are almost pure glucocorticoids, while prednisone, hydrocortisone is typically used for replacement therapy, e. Corticosteroids are also used supportively to prevent nausea, often in combination with 5-HT3 antagonists, typical undesired effects of glucocorticoids present quite uniformly as drug-induced Cushings syndrome. Typical mineralocorticoid side-effects are hypertension, hypokalemia, hypernatremia without causing peripheral edema, metabolic alkalosis, there may also be impaired wound healing or ulcer formation because of the immunosuppressive effects.
Clinical and experimental evidence indicates that corticosteroids can cause permanent eye damage by inducing central serous retinopathy, a variety of steroid medications, from anti-allergy nasal sprays to topical skin creams, to eye drops, to prednisone have been implicated in the development of CSR.
Corticosteroids have been used in treating people with traumatic brain injury. A systematic review identified 20 randomised controlled trials and included 12, participants, the authors recommended people with traumatic head injury should not be routinely treated with corticosteroids.
There is some basis for genetic variation in response to inhaled corticosteroids. Two genes of interest are CHRH1 and TBX21, both genes display some degree of polymorphic variation in humans, which may explain how some patients respond better to inhaled corticosteroid therapy than others. Use of corticosteroids has numerous side-effects, some of which may be severe, Neuropsychiatric, steroid psychosis, therapeutic doses may cause a feeling of artificial well-being.
The neuropsychiatric effects are mediated by sensitization of the body to the actions of adrenaline. Therapeutically, the bulk of corticosteroid dose is given in the morning to mimic the bodys diurnal rhythm, if given at night, an extensive review is provided by Flores and Gumina. Cardiovascular, Corticosteroids can cause sodium retention through an action on the kidney.
This can result in retention and hypertension. Glucocorticoide — Glucocorticoids are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the receptor, that is present in almost every vertebrate animal cell. The name glucocorticoid is composed from its role in regulation of metabolism, synthesis in the adrenal cortex. A less common synonym is glucocorticosteroid, gCs are part of the feedback mechanism in the immune system which reduces certain aspects of immune function, such as reduction of inflammation.
They are therefore used in medicine to treat diseases caused by an immune system, such as allergies, asthma, autoimmune diseases. GCs have many effects, including potentially harmful side effects.
They also interfere with some of the mechanisms in cancer cells. This includes, inhibitory effects on lymphocyte proliferation as in the treatment of lymphomas and leukemias, gCs affect cells by binding to the glucocorticoid receptor. Glucocorticoids are distinguished from mineralocorticoids and sex steroids by their specific receptors, target cells, in technical terms, corticosteroid refers to both glucocorticoids and mineralocorticoids, but is often used as a synonym for glucocorticoid.
Glucocorticoids are chiefly produced in the zona fasciculata of the adrenal cortex, cortisol is the most important human glucocorticoid.
It is essential for life, and it regulates or supports a variety of important cardiovascular, metabolic, immunologic, glucocorticoid effects may be broadly classified into two major categories, immunological and metabolic. In addition, glucocorticoids play important roles in development and body fluid homeostasis. As discussed in detail below, glucocorticoids function through interaction with the glucocorticoid receptor.
Down-regulate the expression of proinflammatory proteins, glucocorticoids are also shown to play a role in the development and homeostasis of T lymphocytes. This has been shown in mice with either increased or decreased sensitivity of T cell lineage to glucocorticoids.
The name glucocorticoid derives from early observations that these hormones were involved in glucose metabolism, in the fasted state, cortisol stimulates several processes that collectively serve to increase and maintain normal concentrations of glucose in blood.
Enhancing the expression of enzymes involved in gluconeogenesis is probably the best-known metabolic function of glucocorticoids, mobilization of amino acids from extrahepatic tissues, These serve as substrates for gluconeogenesis.
Excessive glucocorticoid levels resulting from administration as a drug or hyperadrenocorticism have effects on many systems, some examples include inhibition of bone formation, suppression of calcium absorption, delayed wound healing, muscle weakness, and increased risk of infection. Mineralocorticoide — Mineralocorticoids are a class of corticosteroids, which are a class of steroid hormones. Mineralocorticoids are corticosteroids that influence salt and water balances, the primary mineralocorticoid is aldosterone, notable for an aldehyde group at the 18 position.
The name mineralocorticoid derives from early observations that these hormones were involved in the retention of sodium, the primary endogenous mineralocorticoid is aldosterone, although a number of other endogenous hormones have mineralocorticoid function.
This in turn results in an increase of pressure and blood volume. Mineralocorticoids bind to the receptor in the cell cytosol, and are able to freely cross the lipid bilayer of the cell.
This type of receptor becomes activated upon ligand binding, the opposite mechanism is called transrepression. The hormone receptor without ligand binding interacts with heat shock proteins, aldosterone and cortisol have similar affinity for the mineralocorticoid receptor, however, glucocorticoids circulate at roughly times the level of mineralocorticoids.
An enzyme exists in mineralocorticoid target tissues to prevent overstimulation by glucocorticoids and this enzyme, beta hydroxysteroid dehydrogenase type II, catalyzes the deactivation of glucocorticoids to dehydro metabolites.
Licorice is known to be an inhibitor of this enzyme and chronic consumption can result in a known as pseudohyperaldosteronism. An example of a synthetic mineralocorticoid is fludrocortisone, important antimineralocorticoids are spironolactone and eplerenone. Androgene — This includes the activity of the primary male sex organs and development of male secondary sex characteristics. Androgens were first discovered in , androgens increase in both boys and girls during puberty.
Androgens are also the original anabolic steroids and the precursor of all estrogens, the primary and most well-known androgen is testosterone. Dihydrotestosterone and androstenedione are less known generally, but are of importance in male development. DHT in the embryo life causes differentiation of penis, scrotum, later in life DHT contributes to balding, prostate growth and sebaceous gland activity.
Although androgens are described as sex hormones, both males and females have them to varying degrees, as is also true of estrogens. They are one of three types of sex hormones, the others being estrogens like estradiol and progestogens like progesterone, the main subset of androgens, known as adrenal androgens, is composed of carbon steroids synthesized in the zona reticularis, the innermost layer of the adrenal cortex.
Adrenal androgens function as weak steroids, and the subset includes dehydroepiandrosterone, dehydroepiandrosterone sulfate, androstenedione, besides testosterone, other androgens include, Dehydroepiandrosterone is a steroid hormone produced in the adrenal cortex from cholesterol.
It is the precursor of natural estrogens. DHEA is also called dehydroisoandrosterone or dehydroandrosterone, androstenedione is an androgenic steroid produced by the testes, adrenal cortex, and ovaries. While androstenediones are converted metabolically to testosterone and other androgens, they are also the parent structure of estrone, use of androstenedione as an athletic or bodybuilding supplement has been banned by the International Olympic Committee, as well as other sporting organizations.
Androstenediol is the steroid metabolite thought to act as the regulator of gonadotropin secretion. It is found in equal amounts in the plasma and urine of both males and females. Dihydrotestosterone is a metabolite of testosterone, and a potent androgen than testosterone in that it binds more strongly to androgen receptors. It is produced in the skin and reproductive tissue, during mammalian development, the gonads are at first capable of becoming either ovaries or testes.
In humans, starting at about week 4, the rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, epithelial sex cords develop within the forming testes, in males, certain Y chromosome genes, particularly SRY, control development of the male phenotype, including conversion of the early bipotential gonad into testes. In males, the sex cords fully invade the developing gonads, the mesoderm-derived epithelial cells of the sex cords in developing testes become the Sertoli cells, which will function to support sperm cell formation.
Estrogene — Estrogen or oestrogen is the primary female sex hormone as well as a medication. It is responsible for the development and regulation of the reproductive system. Estrogen may also refer to any substance, natural or synthetic, the estrane steroid estradiol is the most potent and prevalent endogenous estrogen, although several metabolites of estradiol also have estrogenic hormonal activity.
Their presence in both vertebrates and insects suggests that sex hormones have an ancient evolutionary history. The three major naturally occurring forms of estrogen in women are estrone, estradiol, and estriol, another type of estrogen called estetrol is produced only during pregnancy.
Quantitatively, estrogens circulate at lower levels than androgens in both men and women, while estrogen levels are significantly lower in males compared to females, estrogens nevertheless also have important physiological roles in males.
Like all steroid hormones, estrogens readily diffuse across the cell membrane, once inside the cell, they bind to and activate estrogen receptors which in turn modulate the expression of many genes.
Additionally, estrogens bind to and activate rapid-signaling membrane estrogen receptors, the three major naturally occurring estrogens in women are estrone, estradiol, and estriol. Estradiol is the predominant estrogen during reproductive years both in terms of serum levels as well as in terms of estrogenic activity. During menopause, estrone is the predominant circulating estrogen and during pregnancy estriol is the predominant circulating estrogen in terms of serum levels. Though estriol is the most plentiful of the three estrogens it is also the weakest, whereas estradiol is the strongest with a potency of approximately 80 times that of estriol.
Thus, estradiol is the most important estrogen in non-pregnant females who are between the menarche and menopause stages of life, however, during pregnancy this role shifts to estriol, and in postmenopausal women estrone becomes the primary form of estrogen in the body. Another type of estrogen called estetrol is produced only during pregnancy, all of the different forms of estrogen are synthesized from androgens, specifically testosterone and androstenedione, by the enzyme aromatase.
Estradiol, estrone, and estriol have all been approved as drugs and are used medically.
Signaltransduktion und Hormone
Adrenal Steroid Hormone Synthesis -See how to lower cholesterol naturally at: gaytaboo.xyz there's a lot of coagulation cascades out there , but this is by far my favorite wound treatment charts | Management: Mehr dazu . I think the basic hormone cascade chart would have been an invaluable addition. This shows how pregnenolone is the grandmother of all hormones at the top. Aug. Regelwerk im Zellkern | Natürliche Steroidhormone binden sich an . Im europäischen Forschungsnetz Cascade ergründen wir und andere.