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Androgens increase in boys and girls during puberty. The main androgen in men is testosterone. Dihydrotestosterone (DHT) and androstenedione have similar interests in the development of men. DHT in utero causes differentiation of the penis, scrotum and prostate. In adulthood, DHT contributes to balding, prostate growth, and sebaceous gland activity.
Although androgens are generally considered only as male sex hormones, women also have them, but to a lesser extent: they function in libido and sexual arousal. Also, androgens are estrogen precursors in men and women.
In addition to their role as a natural hormone, androgens are used as drugs; for information on androgens as a drug, see androgen replacement therapy and anabolic steroid articles.
Video Androgen
Types and examples
The main part of androgens, known as adrenal androgens, is composed of 19-carbon steroids synthesized in the reticular zone, the innermost layer of the adrenal cortex. Adrenal androgens act as weak steroids (though some precursors), and subset includes dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), androstenedione (A4), and androstenediol (A5).
In addition to testosterone, other androgens include:
- Dehydroepiandrosterone (DHEA) is a steroid hormone produced in the adrenal cortex of cholesterol. This is the main precursor of natural estrogens. DHEA is also called dehydroisoandrosterone or dehydroandrosterone.
- Androstenedione (A4) is an androgenic steroid produced by the testes, the adrenal cortex, and the ovaries. While androstenedione is converted metabolically to testosterone and other androgens, they are also the estrone parent structure. The use of androstenedione as an athletic or bodybuilding supplement has been banned by the International Olympic Committee, as well as other sports organizations.
- Androstenediol (A5) is a steroid metabolite suspected to act as the main regulator of gonadotropin secretion.
- Androsterone is a chemical by-product made during androgen splitting, or derived from progesterone, which also gives a minor masculinising effect, but with all seven testosterone intensities. It is found in approximately the same amount in plasma and urine both men and women.
- Dihydrotestosterone (DHT) is a more potent metabolite of testosterone, and androgen than testosterone because it binds more strongly to androgen receptors. It is produced in the skin and reproductive tissues.
Maps Androgen
Biological function
The development of a male fetus
Testes formation
During the development of mammals, the gonads were initially capable of being ovarian or testicular. In humans, starting around week 4, the basics of gonads are present in intermediate mesoderms adjacent to the developing kidney. Around week 6, epithelial sex ropes develop within the forming testicles and combine germ cells when they migrate to the gonads. In males, certain Y chromosome genes, especially SRY, control the development of male phenotype, including the conversion of early bipotential gonads into testes. In men, the genital strap completely attacks the growing gonads.
Androgen Production
The mesoderm epithelial cells derived from sex ropes develop the testes into Sertoli cells, which will serve to support the formation of sperm cells. Small populations of nonepithelial cells appear among tubules at the 8th week of human fetal development. This is the Leydig cell. As soon as they differentiate, Leydig cells begin to produce androgens.
Androgen effect
Androgens function as paracrine hormones needed by Sertoli cells to support sperm production. They are also needed for masculinization of developing male fetuses (including penis and scrotum formation). Under the influence of androgens, the remains of the mesonephron, the Wolffia duct, develop into epididymis, vas deferens, and seminal vesicles. This androgen action is supported by the hormone of the Sertoli cell, the MÃÆ'¼llerian (MIH) inhibiting hormone, which prevents the embryonic Müllerian ducts from developing into fallopian tubes and other female reproductive tissues in male embryos. MIH and androgens work together to allow the movement of the testes into the scrotum.
Initial rule
Before the production of pituitary luteinizing hormone (LH) hormone (LH) by embryos starting around week 11-12, human chorionic gonadotrophin (hCG) promoted Leydig cell differentiation and their androgen production at week 8. Androgen action on target tissue often involves converting testosterone to 5? -dihydrotestosterone (DHT).
The development of male puberty
At puberty, androgen levels increase dramatically in men, and androgens mediate the development of secondary sexual characteristics of masculine as well as the activation of spermatogenesis and fertility and changes in masculine behavior such as gynephilia and increased sex drive. Secondary sexual characteristics of the masculine include androgenic hair, deepening of sound, the appearance of the Adam's apple, shoulder width, increased muscle mass, and penile growth.
Spermatogenesis
During puberty, androgens, LH and follicle stimulating hormone (FSH) increase production and sex ropes loosen, forming seminiferous tubules, and germ cells begin to differentiate into sperm. Throughout adulthood, androgens and FSHs work together on Sertoli cells in the testes to support sperm production. Exogenous androgen supplements can be used as male contraceptives. Increased androgen levels caused by the use of androgen supplements can inhibit LH production and block endogenous androgen production by Leydig cells. Without high local androgen levels in the testes due to androgen production by Leydig cells, the seminiferous tubules may degenerate, resulting in infertility. For this reason, many transdermal androgen patches are applied to the scrotum.
Fatty deposits
Men usually have less body fat than women. Recent results suggest androgens inhibit the ability of some fat cells to store lipids by blocking signal transduction pathways that normally support adipocyte function. Also, androgens, but not estrogens, increase adrenergic beta receptors while reducing alpha-adrenergic receptors - resulting in elevated levels of epinephrine/norepinephrine due to lack of feedback of alpha-2 receptors and decreased fat accumulation because epinephrine/norepinephrine then works on lipolysis. -induced beta receptor.
Muscle mass
Men usually have more skeletal muscle mass than women. Androgens increase the enlargement of skeletal muscle cells and may act in a coordinated way to function by acting on several types of cells in skeletal muscle tissue. One type of cell conveys hormone signals to produce muscle, myoblast. Higher androgen levels lead to increased expression of androgen receptors. The myoblastic combination produces myotubes, in a process associated with the androgen receptor level.
Brain
The rate of androgen circulation can affect human behavior because some neurons are sensitive to steroid hormones. Androgen levels have been implicated in the regulation of human aggression and libido. Indeed, androgens are able to alter brain structures in some species, including mice, rats, and primates, resulting in sex differences.
Many reports have shown that androgens alone are capable of altering brain structure, but identification of which changes in the neuroanatomic stems of androgens or estrogens is difficult, because of their potential for conversion.
Evidence from neurogenesis (the formation of new neurons) studies in male rats suggests that the hippocampus is a useful brain area to be examined when determining the effect of androgens on behavior. To test for neurogenesis, wild-type wild rats were compared with male mice subjected to testicular feminization mutations (TMF), genetic disorders resulting in total or partial insensitivity to androgens and lack of external male genitalia.
Bromodeoxyuridine (BrdU) nerve injections were applied to men from both groups to test for neurogenesis. The analysis showed that testosterone and dihydrotestosterone regulate adult hippocampal neurogenesis (AHN). Adult hippocampal neurogenesis is regulated through androgen receptors in wild-type males, but not in TMF male mice. To further test the role of active androgen receptors in AHN, flutamide, antiandrogen drugs that compete with testosterone and dihydrotestosterone for androgen receptors, and dihydrotestosterone is administered to normal male rats. Dihydrotestosterone increases the number of BrdU cells, while flutamide inhibits these cells.
Moreover, estrogen has no effect. This study shows how androgens can improve AHN.
The researchers also examined how moderate exercise affects androgen synthesis which in turn leads to the activation of the N-methyl-D-aspartate (NMDA) receptor AHN.
NMDA induces calcium flux that allows synaptic plasticity that is essential for AHN.
The researchers injected either orchidectomy (ORX) (castrated) and male rats castrated with BrdU to determine whether new cell counts increased. They found that AHN in male rats increased with mild exercise by increasing the synthesis of dihydrotestosterone in the hippocampus.
Again it is noted that AHN does not increase through activation of estrogen receptors.
Androgen regulation decreases the likelihood of depression in men. In preteen males, neonatal mice treated with flutamide experienced more symptoms such as depression than control mice.
Again BrdU is injected into both groups of mice to see if cells multiply in living tissue. These results show how androgen organizations have a positive effect on the hippocampal preadolescent neurogenesis that may be associated with symptoms such as lower depression.
Social isolation has an inhibiting effect in AHN whereas normal androgen regulation improves AHN. A study using male rats indicates that testosterone can block social isolation, which results in a hippocampal neurogenesis reaching homeostasis - a regulation that keeps internal conditions stable. Brdu analysis showed that excess testosterone did not increase the blocking effect on social isolation; that is, the levels of androgens in circulation naturally cancel the negative effects of social isolation on AHN.
Female special effects
Androgens have a potential role in the relaxation of the myometrium through non-genomic pathways, androgens of independent receptors, preventing premature uterine contractions in pregnancy.
Androgen's insensitivity
Reducing the ability of the fetus XY-karotype to respond to androgens can cause one of several conditions, including infertility and some form of intersex conditions.
Miscellaneous
The yellow androgen level in certain birds has been positively correlated with social dominance in the future. See American coot.
Biological activity
Androgens binds and activates androgen receptors (AR) to mediate most of its biological effects.
Relative potential
Determined by consideration of all biological testing methods (circa 1970):
5? -Dihydrotestosterone (DHT) is 2.4 times stronger than testosterone in maintaining normal prostate weight and lumen ductal mass (this is a measure of stimulation of epithelial cell function). While DHT is equally powerful as testosterone in preventing prostate cell death after castration.
Non-genomic actions
Androgens have also been found to signal through membrane androgen receptors, which are distinct from classical nuclear androgen receptors.
Biochemistry
Biosynthesis
Androgens are synthesized from cholesterol and are produced mainly in the gonads (testicles and ovaries) as well as in the adrenal glands. The testes produce a much higher number than the ovaries. More potent conversion of testosterone to DHT occurs in the prostate gland, liver, brain and skin.
Metabolism
Androgens are metabolized primarily in the liver.
Medical use
Low testosterone levels (hypogonadism) in men can be treated by administering testosterone. Prostate cancer can be treated by removing the primary source of testosterone: removal of the testes (orchiectomy); or an agent that blocks androgens from accessing its receptor: antiandrogen.
See also
- Andrology
- The endocrine system
- Exercise and androgen levels
- Androgen insensitivity syndrome
- Testosterone and cardiovascular system
- Abbreviations of steroid
- List of androgen/anabolic steroids
- List of androgen/anabolic steroids available in the United States
References
Source of the article : Wikipedia
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