Around 50% of ageing, obese men presenting to the diabetes clinic have lowered testosterone levels relative to reference ranges
based on healthy young men
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The Aging Male Hypothalamic-Pituitary-Gonadal Axis: pulsatility and feedback - 0 views
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Testosterone and glucose metabolism in men: current concepts and controversies - 0 views
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Low T Testosterone metabolic syndrome MetS Diabetes men male glucose hormone hormones g
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The absence of high-level evidence in this area is illustrated by the Endocrine Society testosterone therapy in men with androgen deficiency clinical practice guidelines (Bhasin et al. 2010), which are appropriate for, but not specific to men with metabolic disorders. All 32 recommendations made in these guidelines are based on either very low or low quality evidence.
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A key concept relates to making a distinction between replacement and pharmacological testosterone therapy
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Findings similar to type 2 diabetes were reported for men with the metabolic syndrome, which were associated with reductions in total testosterone of −2.2 nmol/l (95% CI −2.41 to 1.94) and in free testosterone
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Cross-sectional studies uniformly show that 30–50% of men with type 2 diabetes have lowered circulating testosterone levels, relative to references based on healthy young men
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In a recent cross-sectional study of 240 middle-aged men (mean age 54 years) with either type 2 diabetes, type 1 diabetes or without diabetes (Ng Tang Fui et al. 2013b), increasing BMI and age were dominant drivers of low total and free testosterone respectively.
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both diabetes and the metabolic syndrome are associated with a modest reduction in testosterone, in magnitude comparable with the effect of 10 years of ageing
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In a cross-sectional study of 490 men with type 2 diabetes, there was a strong independent association of low testosterone with anaemia
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In men, low testosterone is a marker of poor health, and may improve our ability to predict risk
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It remains possible that low testosterone is a consequence of insulin resistance, or simply a biomarker, co-existing because of in-common risk factors.
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In prospective studies, reviewed in detail elsewhere (Grossmann et al. 2010) the inverse association of low testosterone with metabolic syndrome or diabetes is less consistent for free testosterone compared with total testosterone
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In a study from the Framingham cohort, SHBG but not testosterone was prospectively and independently associated with incident metabolic syndrome
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low SHBG (Ding et al. 2009) but not testosterone (Haring et al. 2013) with an increased risk of future diabetes
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In cross-sectional studies of men with (Grossmann et al. 2008) and without (Bonnet et al. 2013) diabetes, SHBG but not testosterone was inversely associated with worse glycaemic control
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SHBG may have biological actions beyond serving as a carrier protein for and regulator of circulating sex steroids
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In men with diabetes, free testosterone, if measured by gold standard equilibrium dialysis (Dhindsa et al. 2004), is reduced
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Low free testosterone remains inversely associated with insulin resistance, independent of SHBG (Grossmann et al. 2008). This suggests that the low testosterone–dysglycaemia association is not solely a consequence of low SHBG.
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Experimental evidence reviewed below suggests that visceral adipose tissue is an important intermediate (rather than a confounder) in the inverse association of testosterone with insulin resistance and metabolic disorders.
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testosterone promotes the commitment of pluripotent stem cells into the myogenic lineage and inhibits their differentiation into adipocytes
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testosterone regulates the metabolic functions of mature adipocytes (Xu et al. 1991, Marin et al. 1995) and myocytes (Pitteloud et al. 2005) in ways that reduce insulin resistance.
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Pre-clinical evidence (reviewed in Rao et al. (2013)) suggests that at the cellular level, testosterone may improve glucose metabolism by modulating the expression of the glucose-transported Glut4 and the insulin receptor, as well as by regulating key enzymes involved in glycolysis.
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More recently testosterone has been shown to protect murine pancreatic β cells against glucotoxicity-induced apoptosis
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Interestingly, a reciprocal feedback also appears to exist, given that not only chronic (Cameron et al. 1990, Allan 2013) but also, as shown more recently (Iranmanesh et al. 2012, Caronia et al. 2013), acute hyperglycaemia can lower testosterone levels.
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In men with prostate cancer commencing androgen deprivation therapy, both total as well as, although not in all studies (Smith 2004), visceral fat mass increases (Hamilton et al. 2011) within 3 months
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More prolonged (>12 months) androgen deprivation therapy has been associated with increased risk of diabetes in several large observational registry studies
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Testosterone has also been shown to reduce the concentration of pro-inflammatory cytokines in some, but not all studies, reviewed recently in Kelly & Jones (2013). It is not know whether this effect is independent of testosterone-induced changes in body composition.
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the observations discussed in this section suggest that it is the decrease in testosterone that causes insulin resistance and diabetes. One important caveat remains: the strongest evidence that low testosterone is the cause rather than consequence of insulin resistance comes from men with prostate cancer (Grossmann & Zajac 2011a) or biochemical castration, and from mice lacking the androgen receptor.
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Several large prospective studies have shown that weight gain or development of type 2 diabetes is major drivers of the age-related decline in testosterone levels
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there is increasing evidence that healthy ageing by itself is generally not associated with marked reductions in testosterone
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increased visceral fat is an important component in the association of low testosterone and insulin resistance
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The vast majority of men with metabolic disorders have functional gonadal axis suppression with modest reductions in testosterone levels
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men with Klinefelter syndrome have an increased risk of metabolic disorders. Interestingly, greater body fat mass is already present before puberty
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inhibition of the gonadal axis predominantly takes place in the hypothalamus, especially with more severe obesity
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Metabolic factors, such as leptin, insulin (via deficiency or resistance) and ghrelin are believed to act at the ventromedial and arcuate nuclei of the hypothalamus to inhibit gonadotropin-releasing hormone (GNRH) secretion from GNRH neurons situated in the preoptic area
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hypothesis that obesity-mediated inhibition of kisspeptin signalling contributes to the suppression of the HPT axis, infusion of a bioactive kisspeptin fragment has been recently shown to robustly increase LH pulsatility, LH levels and circulating testosterone in hypotestosteronaemic men with type 2 diabetes
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A smaller study with a similar experimental design found that acute testosterone withdrawal reduced insulin sensitivity independent of body weight, whereas oestradiol withdrawal had no effects
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Obesity and dysglycaemia and associated comorbidities such as obstructive sleep apnoea (Hoyos et al. 2012b) are important contributors to the suppression of the HPT axis
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Modifiable risk factors such as obesity and co-morbidities are more strongly associated with a decline in circulating testosterone levels than age alone
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55% of symptomatic androgen deficiency reverted to a normal testosterone or an asymptomatic state after 8-year follow-up, suggesting that androgen deficiency is not a stable state
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The hypothalamic–pituitary–testicular axis remains responsive to treatment with aromatase inhibitors or selective oestrogen receptor modulators in obese men
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Kisspeptin treatment increases LH secretion, pulse frequency and circulating testosterone levels in hypotestosteronaemic men with type 2 diabetes
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weight loss can lead to genuine reactivation of the gonadal axis by reversal of obesity-associated hypothalamic suppression
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There is pre-clinical and observational evidence that chronic hyperglycaemia can inhibit the HPT axis
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in men who improved their glycaemic control over time, testosterone levels increased. By contrast, in those men in whom glycaemic control worsened, testosterone decreased
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testosterone levels should be measured after successful weight loss to identify men with an insufficient rise in their testosterone levels. Such men may have HPT axis pathology unrelated to their obesity, which will require appropriate evaluation and management.
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Gonadal dysfunction in systemic diseases - 0 views
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Gut Endotoxin Leading to a Decline IN Gonadal function (GELDING) - a novel theory for t... - 0 views
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GELDING theory GELDING LPS gut gut health inflammation low T low Testosterone Testosterone hypogonadism obesity
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trans-mucosal passage of bacterial lipopolysaccharide (LPS) from the gut lumen into the circulation is a key inflammatory trigger underlying male hypogonadism
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Obesity and a high fat/high calorie diet are both reported to result in changes to gut bacteria and intestinal wall permeability, leading to the passage of bacterial endotoxin (lipopolysaccharide- LPS) from within the gut lumen into the circulation (metabolic endotoxaemia), where it initiates systemic inflammation.
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Endotoxin is known to reduce testosterone production by the testis, both by direct inhibition of Leydig cell steroidogenic pathways and indirectly by reducing pituitary LH drive, thereby also leading to a decline in sperm production.
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Testosterone and glucose metabolism in men: current concepts and controversies - 0 views
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Only 5% of men with type 2 diabetes have elevated LH levels (Dhindsa et al. 2004, 2011). This is consistent with recent findings that the inhibition of the gonadal axis predominantly takes place in the hypothalamus, especially with more severe obesity
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Metabolic factors, such as leptin, insulin (via deficiency or resistance) and ghrelin are believed to act at the ventromedial and arcuate nuclei of the hypothalamus to inhibit gonadotropin-releasing hormone (GNRH) secretion
- ...32 more annotations...
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Consistent with the hypothesis that obesity-mediated inhibition of kisspeptin signalling contributes to the suppression of the HPT axis, infusion of a bioactive kisspeptin fragment has been recently shown to robustly increase LH pulsatility, LH levels and circulating testosterone in hypotestosteronaemic men with type 2 diabetes
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Interestingly, a recent 16-week study of experimentally induced hypogonadism in healthy men with graded testosterone add-back either with or without concomitant aromatase inhibitor treatment has in fact suggested that low oestradiol (but not low testosterone) may be responsible for the hypogonadism-associated increase in total body and intra-abdominal fat mass
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A smaller study with a similar experimental design found that acute testosterone withdrawal reduced insulin sensitivity independent of body weight, whereas oestradiol withdrawal had no effects
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Obesity and dysglycaemia and associated comorbidities such as obstructive sleep apnoea (Hoyos et al. 2012b) are important contributors to the suppression of the HPT axis
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This is supported by observational studies showing that weight gain and development of diabetes accelerate the age-related decline in testosterone
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The hypothalamic–pituitary–testicular axis remains responsive to treatment with aromatase inhibitors or selective oestrogen receptor modulators in obese men
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Kisspeptin treatment increases LH secretion, pulse frequency and circulating testosterone levels in hypotestosteronaemic men with type 2 diabetes
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Several observational and randomised studies reviewed in Grossmann (2011) have shown that weight loss, whether by diet or surgery, leads to substantial increases in testosterone, especially in morbidly obese men
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This suggests that weight loss can lead to genuine reactivation of the gonadal axis by reversal of obesity-associated hypothalamic suppression
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There is pre-clinical and observational evidence that chronic hyperglycaemia can inhibit the HPT axis
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successful weight loss combined with optimisation of glycaemic control may be sufficient to normalise circulating testosterone levels in the majority of such men
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weight loss, optimisation of diabetic control and assiduous care of comorbidities should remain the first-line approach.
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In part, the discrepant results may be due to the fact men in the Vigen cohort (Vigen et al. 2013) had a higher burden of comorbidities. Given that one (Basaria et al. 2010), but not all (Srinivas-Shankar et al. 2010), RCTs in men with a similarly high burden of comorbidities reported an increase in cardiovascular events in men randomised to testosterone treatment (see section on Testosterone therapy: potential risks below) (Basaria et al. 2010), testosterone should be used with caution in frail men with multiple comorbidities
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The retrospective, non-randomised and non-blinded design of these studies (Shores et al. 2012, Muraleedharan et al. 2013, Vigen et al. 2013) leaves open the possibility for residual confounding and multiple other sources of bias. These have been elegantly summarised by Wu (2012).
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Effects of testosterone therapy on body composition were metabolically favourable with modest decreases in fat mass and increases in lean body mass
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This suggests that testosterone has limited effects on glucose metabolism in relatively healthy men with only mildly reduced testosterone.
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it is conceivable that testosterone treatment may have more significant effects on glucose metabolism in uncontrolled diabetes, akin to what has generally been shown for conventional anti-diabetic medications.
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the evidence from controlled studies show that testosterone therapy consistently reduces fat mass and increases lean body mass, but inconsistently decreases insulin resistance.
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Interestingly, testosterone therapy does not consistently improve glucose metabolism despite a reduction in fat mass and an increase in lean mass
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the majority of RCTs (recently reviewed in Ng Tang Fui et al. (2013a)) showed that testosterone therapy does not reduce visceral fat
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testosterone is inversely associated with total cholesterol, LDL cholesterol and triglyceride (Tg) levels, but positively associated with HDL cholesterol levels, even if adjusted for confounders
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Although observational studies show a consistent association of low testosterone with adverse lipid profiles, whether testosterone therapy exerts beneficial effects on lipid profiles is less clear
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Whereas testosterone-induced decreases in total cholesterol, LDL cholesterol and Lpa are expected to reduce cardiovascular risk, testosterone also decreases the levels of the cardio-protective HDL cholesterol. Therefore, the net effect of testosterone therapy on cardiovascular risk remains uncertain.
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data have not shown evidence that testosterone causes prostate cancer, or that it makes subclinical prostate cancer grow
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compared with otherwise healthy young men with organic androgen deficiency, there may be increased risks in older, obese men because of comorbidities and of decreased testosterone clearance
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Acute effects of interferon-alpha administration on testosterone concentrations in heal... - 0 views
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interferon hepatitis Hepatitis C low T low Testosterone Testosterone FAI free Androgen Index men male hormone hormones
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http://www.researchgate.net/profile/Costanzo_Moretti/publication/12777565_Leptin_and_an... - 0 views
www.researchgate.net/...02bfe50e5334207a93000000.pdf
leptin low T low Testosterone obese men male hormone hormones obesity
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Normal leptin levels are critical to puberty; but in obese men, increased leptin is associated with gonadal decrease in Testosterone. It appears to occur through a decrease in 17-OH progesterone to Testosterone: suggesting an inhibitory activity in the conversion of 17-OH progesterone to Testosterone in obese men.
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Antagonistic interplay between hypocretin and leptin in the lateral hypothalamus regula... - 0 views
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http://joe.endocrinology-journals.org/content/170/2/413.full.pdf - 0 views
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Effect of amlodipine, a calcium channel antagonist, on gonadal steroid - 0 views
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Effects of chronic celecoxib on testicular function in normal and lipopolysaccharide-tr... - 0 views
www.ncbi.nlm.nih.gov/...18522674
low Testosterone Testosterone male hormones inflammation LPS lipopolysaccharides
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Animal study from '09 found that COX2 inhibitor blunted LPS decrease in testes weight, decrease in testicular interstitial fluid, and serum Testosterone. The point here is that LPS, in this animal model, decreased gonadal weight and Testosterone production and the anti inflammatory, COX2, blunted that effect.
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Adrenal and gonadal steroid hormone deficiency in the pathogenesis of rheumatoid arthri... - 0 views
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11-Ketotestosterone Is a Major Androgen Produced in Human Gonads: The Journal of Clinic... - 0 views
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Vitamin D is associated with testosterone and hypogonadism in Chinese men: Results from... - 0 views
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lower 25(OH)D level was significantly associated with lower total T, E2, SHBG, LH and FSH levels after adjusting for age, residence area, economic status and current smoker
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association between 25(OH)D status and hypogonadism in Chinese men and confirms that this relationship is present in a large population
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Another mouse study reported a tendency towards low testosterone/LH ratio and Leydig cell hyperplasia in VDR null mice
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The serum testosterone levels could increase to normal values in vitamin D-deficient rats replete with vitamin D
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VDR knockout mice had decreased sperm count, reduced sperm motility, and histological abnormality of the testis
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The data from the European Male Ageing Study [9] indicated that 25(OH)D is positively associated with total T
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Progesterone metabolites in breast cancer - 1 views
erc.endocrinology-journals.org/...717.full
progesterone metabolism tumor tumorigenesis cancer risk growth hormone hormones 5-beta-pregnanediol 5-alpha-pregnanediol 4-pregnenediol 5-alpha reductase
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P metabolites produced within breast tissues might be independently active hormones functioning as cancer-promoting or -inhibiting regulatory agents
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these P metabolites function as independent pro-or anti-cancer autocrine/paracrine hormones that regulate cell proliferation, adhesion, apoptosis and cytoskeletal, and other cell status molecules via novel receptors located in the cell membrane and intrinsically linked to cell signaling pathways
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only a fraction of all breast cancer patients respond to this estrogen-based therapy and the response is only temporary
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P serves as the precursor for the major steroid hormones (androgens, estrogens, corticosteroids) produced by the gonadal and adrenal cortical tissues.
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These P-metabolizing enzymes included 5α-reductase, 5β-reductase, 3α-hydroxysteroid oxido-reductase (3α-HSO), 3β-HSO, 20α-HSO, 20β-HSO, 6α(β)-, 11β-, 17-, and 21-hydroxylase, and C17–20-lyase
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Reduction of P to 5α-pregnanes is catalyzed by 5α-reductase and the direct 5α-reduced metabolite of P is 5α-pregnane-3,20-dione (5αP). The 5α-reductase reaction is irreversible
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The two 4-pregnenes resulting from direct P conversion are 4-pregnen-3α-ol-20-one (3αHP) and 4-pregnen-20α-ol-3-one (20αHP), catalyzed by the actions of 3α-HSO and 20α-HSO respectively
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the P-metabolizing enzyme activities identified in human breast tissues and cell lines were: 5α-reductase, 3α-HSO, 3β-HSO, 20α-HSO, and 6α-hydroxylase
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In normal breast tissue, conversion to 4-pregnenes greatly exceeded the conversion to 5α-pregnanes, whereas in tumorous tissue, conversion to 5α-pregnanes greatly exceeded that to 4-pregnenes
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The results indicated that P 5α-reductase activity is significantly higher, whereas P 3α-HSO and 20α-HSO activities are significantly lower in tumor than in normal tissues
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he results showed that production of 5α-pregnanes was higher and that of 4-pregnenes was lower in tumorigenic (e.g. MCF-7) than in nontumorigenic (e.g. MCF-10A) cells (Fig. 3c⇑), while differences in ER/P status did not appear to play a role
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The 5α-pregnane-to-4-pregnene ratios were 7- to 20-fold higher in the tumorigenic than in the nontumorigenic cell lines
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altered direction in P metabolism, and hence in metabolite ratios, was due to significantly elevated 5α-reductase and depressed 3α- and 20α-HSO activities in breast tumor tissues and tumorigenic cells. It appeared, therefore, that changes in P-metabolizing enzyme activities might be related to the shift toward mammary cell tumorigenicity and neoplasia
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In vivo, changes in enzyme activity can result from changes in levels of the enzyme due to changes in expression of the mRNA coding for the enzyme, or from changes in the milieu in which the enzyme operates (such as temperature and pH, and concentrations of cofactors, substrates, products, competitors, ions, phospholipids, and other molecules)
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Overall, the enzyme activity and expression studies strongly suggest that 5α-reductase stimulation and 3α- and 20α-HSO suppression are associated with the transition from normalcy to cancer of the breast
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The level of expression of 5α-reductase is up-regulated by estradiol and P in the uterus (Minjarez et al. 2001) and by 5α-dihydrotestosterone (DHT) in the prostate
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Stimulation in cell numbers was also observed when cells were treated with other 5α-pregnanes, such as 5α-pregnan-3α-ol-20-one, 5α-pregnan-20α-ol-3-one, and 5α-pregnane-3α,20α-diol, whereas other 4-pregnenes such as 20α-HP and 4-pregnene-3α,20α-diol resulted in suppression of cell proliferation
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Stimulation of cell proliferation with 5αP and inhibition with 3αHP were also observed in all other breast cell lines examined, whether ER/P-negative (MCF-10A, MDA-MB-231) or ER/P-positive (T47D, ZR-75-1) and whether requiring estrogen for tumorigenicity (MCF-7, T47D) or not (MDA-MB-231), or whether they are nontumorigenic (
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αHP resulted in significant increases in apoptosis and decreases in mitosis, leading to significant decreases in total cell numbers. In contrast, treatment with 5αP resulted in decreases in apoptosis and increases in mitosis.
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The opposing actions of 5αP and 3αHP on both cell anchorage and proliferation strengthen the hypothesis that the direction of P metabolism in vivo toward higher 5α-pregnane and lower 4-pregnene concentrations could promote breast neoplasia and lead to malignancy.
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The studies showed that binding of 5αP or 3αHP occurs in the plasma membrane fractions, but not in the nuclear or cytosolic compartments
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separate high-specificity, high-affinity, low- capacity receptors for 5αP and 3αHP that are distinct from each other and from the well-studied nuclear/cytosolic P, estrogen, and androgen and corticosteroid receptors
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The studies thus provided the first demonstration of the existence of specific P metabolite receptors
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the receptor results suggest that the putative tumorigenic actions of 5αP may be significantly augmented by the estradiol-induced increases in 5αP binding and decreases in 3αHP binding.
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Estradiol and 5αP resulted in significant dose-dependent increases, whereas 3αHP and 20αHP each resulted in dose-dependent decreases in total ER
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In combination, estradiol + 5αP or 3αHP + 20αHP resulted in additive increases or decreases respectively in ER numbers.
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The data suggest that the action of 5αP on breast cancer cells involves modulation of the MAPK signaling pathway
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current evidence does not appear to support the notion that increased 5α-reductase activity/ expression might significantly alter androgen influences on breast tumor growth.
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Bentham Science Publishers - 0 views
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Gonadal status and outcome of bariatric surgery in obese men - Aarts - 2013 - Clinical ... - 0 views
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low T Testosterone overweight obese bariatric surgery men male hormone hormones free testosterone
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Roles of the gonadal steroid hormones in psychiatric depression in men and women - Rese... - 0 views
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depression estradiol estrogen men Testosterone women hormones hormone
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Gonadal hormone levels and platelet tryptophan and serotonin concentrations in perimeno... - 0 views
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depression tryptophan serotonin women perimenopause menopause
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