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Testosterone is used as a medication for the treatment of male hypogonadism, gender dysphoria, and certain types of breast cancer. As demonstrated by a meta-analysis, substitution therapy with testosterone results in a significant reduction of inflammatory markers. Attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Conflicting results have been obtained concerning the importance of testosterone in maintaining cardiovascular health. In people who have undergone testosterone deprivation therapy, testosterone increases beyond the castrate level have been shown to increase the rate of spread of an existing prostate cancer. These include adult-type body odor, increased oiliness of skin and hair, acne, pubarche (appearance of pubic hair), axillary hair (armpit hair), growth spurt, accelerated bone maturation, and facial hair. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–7 months of age.
Testosterone may prove to be an effective treatment in female sexual arousal disorders, and is available as a dermal patch. Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal. Men who watch a sexually explicit movie have an average increase of 35% in testosterone, peaking at 60–90 minutes after the end of the film, but no increase is seen in men who watch sexually neutral films. This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction. Every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a novel female.
Studies have found that testosterone facilitates aggression by modulating vasopressin receptors in the hypothalamus. About half of studies have found a relationship and about half, no relationship. have been undertaken on the relationship between more general aggressive behavior, and feelings, and testosterone.|At about the same time, Hall and Eik-Nes and Ewing and Eik-Nes showed that pituitary gonadotropic hormones stimulate androgen formation by testes in vitro and ex vivo. About 60 years after that, Baillie demonstrated that these cells contain the enzyme 3β-hydroxysteroid dehydrogenase . Fifty years later, Bouin and Ancel first suggested that androgens are produced by the interstitial Leydig cells .|The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. Both the free fraction and the one bound to albumin are available at the tissue level (their sum constitutes the bioavailable testosterone), while SHBG effectively and irreversibly inhibits the action of testosterone. At the tissue level, testosterone dissociates from albumin and quickly diffuses into the tissues. This binding plays an important role in regulating the transport, tissue delivery, bioactivity, and metabolism of testosterone. As a result, testosterone which is not bound to SHBG is called free testosterone. Fairer offers from test subjects with higher testosterone in the original study increase the likeliness of the offer being accepted by the negotiating partner, therefore decreasing the probability of both participants leaving without any money. However men with high testosterone were significantly 27% less generous in an ultimatum game.|Cholesterol translocation to the inner mitochondrial membrane is mediated by a protein complex formed at mitochondrial contact sites that consists of the cholesterol binding translocator protein, voltage dependent anion channel, and other mitochondrial and cytosolic proteins. Leydig cells are named after the German anatomist Franz Leydig, who discovered them in 1850. When overgrown the OLCs can cause abnormally high androgen levels.|During the first 2–3 postnatal weeks in rats, fetal Leydig cells are gradually replaced by adult Leydig cells 8, 21. The observation that fetal and adult Leydig cells express different genes suggests that the two cell populations arise and function distinctly . Although plasma LH levels remain high at the end of gestation, regression of fetal Leydig cells begins during late fetal life and continues thereafter 15–18. In the mouse, the fetal Leydig cells produce androstenedione which is then converted into testosterone by the fetal Sertoli cells 11, 12. In the mouse, cells expressing steroidogenic factor 1 (SF-1; NR5A1) give rise to the fetal Leydig cells 8, 9.|In the next step, two additional carbon atoms are removed by the CYP17A1 (17α-hydroxylase/17,20-lyase) enzyme in the endoplasmic reticulum to yield a variety of C19 steroids. The first step in the biosynthesis involves the oxidative cleavage of the side-chain of cholesterol by cholesterol side-chain cleavage enzyme (P450scc, CYP11A1), a mitochondrial cytochrome P450 oxidase with the loss of six carbon atoms to give pregnenolone. In contrast to testosterone, DHEA and DHEA sulfate have been found to act as high-affinity agonists of these receptors. The bones and the brain are two important tissues in humans where the primary effect of testosterone is by way of aromatization to estradiol.|Other names for your testicles are male gonads or testes (pronounced "teh-steez"). These body parts make sperm and hormones. A testicle (pronounced "teh-stuh-kl") is part of the male anatomy. Testosterone and the classical nuclear androgen receptor first appeared in gnathostomes (jawed vertebrates).|Although there are methods by which to increase serum testosterone without TRT, including hCG or aromatase inhibitors for men with secondary hypogonadism, these approaches typically are ineffective in men with primary hypogonadism . Thus, exogenous testosterone administration is inappropriate for men who wish to father children 119–120. There are also reports suggesting that exogenous testosterone treatment might increase the risk of prostate cancer .|On the other hand, elevated testosterone in men may increase their generosity, primarily to attract a potential mate. Testosterone levels play a major role in risk-taking during financial decisions. Men who produce more testosterone are more likely to engage in extramarital sex. Men who produce less testosterone are more likely to be in a relationship or married, and men who produce more testosterone are more likely to divorce. However, the testosterone changes observed do not seem to be maintained as relationships develop over time. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.}
In agreement with these findings, Barron and colleagues generated TSPO KO mice that showed reduced total steroidogenic output and age-dependent androgen deficiency . Notably, increased accumulation of lipid droplets was seen in Leydig cells of the knockouts, suggesting an effect on lipid homeostasis in the testis. Although studies conducted over the course of many years and by many labs concluded that TSPO plays a significant role in steroid biosynthesis, this conclusion recently has been called into question 91–94. The OMM proteins TSPO and VDAC, together with the IMM proteins ATAD3 and CYP11A1, are part of the larger 800-kDa metabolon composed of proteins that bring cholesterol directly to CYP11A1 for metabolism.
Clearly, further investigation is needed to clarify and extend our understanding of the relationships among TSPO, STAR, γ and ɛ, and other proteins of the transduceosome in relation to steroidogenesis in Leydig and adrenal cells, as well as in other steroidogenic cells. For example, potential compensatory mechanisms may become involved in steroid formation when TSPO is knocked out in cells or in animals, and particularly so in the latter case when the knockouts are in vivo. Additionally, it is technically challenging to be certain as to whether the effects seen on steroidogenesis in such studies were affected by TSPO knockdown alone or reduced cell viability . The proteins were found to be hormonally induced and to function at the initiation of steroidogenesis by delaying maximal steroidogenesis in MA-10 mouse tumor Leydig cells. Numerous studies have suggested that cholesterol translocation is mediated by the formation of a mitochondrial scaffold, the transduceosome, created by protein–protein interactions of cytosolic and outer mitochondrial membrane proteins . The two classes of enzymes involved in testosterone biosynthesis, the cytochrome P450 proteins of the mitochondria and the hydroxysteroid dehydrogenases of the smooth endoplasmic reticulum, catalyze the conversion of cholesterol to testosterone (Figure 2).
Testosterone administered by gels and other transdermal methods are easier to use and produce more constant testosterone concentrations. The testosterone preparations in use are injections; scrotal and nonscrotal transdermal patches; and oral, buccal, and gel preparations 112–114. The availability of new forms of testosterone supplementation and consumer marketing have contributed to prescription testosterone sales having increased 500% since 1993, with particularly dramatic increases in the USA since 2000 . - http://git.cherrypeng.com/audrahung7621
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