Group items matching

in title, tags, annotations or url

There is little data to support the withholding of T therapy on the basis of concern for precipitating prostate cancer.

Both intervention data and physiology studies point to minimal effects on the prostate gland when serum T levels are increased to the mid-normal range with T therapy

an individualized care plan to assess the possible risks and benefits of T therapy for each patient is critical to optimizing the use of androgens in male health.

the intraprostatic synthesis of testosterone from adrenal-derived precursors likely accounts for the relatively high testosterone levels in prostate after ADT

In addition, AR activity in these cells is likely further enhanced by multiple mechanisms that sensitize AR to low levels of androgens

higher affinity ligand DHT (approximately eightfold higher affinity

type 2 5α-reductase (SRD5A2) being the major enzyme in prostate

reduce DHT to 5α-androstane-3α,17β-diol (3α-androstanediol; Ji et al. 2003, Rizner et al. 2003), which is then glucuronidated to form 3α-androstanediol glucuronide by the enzymes UDP glycosyltransferase 2, B15 (UGT2B15) or UGT2B17

DHT in prostate is inactivated by the enzyme AKR1C2, which is also termed 3α-hydroxysteroid dehydrogenase type 3 (3α-HSD type 3

AKR1C1, is also expressed in prostate. However, in contrast to AKR1C2, it converts DHT primarily to 5α-androstane-3β,17β-diol (3β-androstanediol; Steckelbroeck et al. 2004), which is a potential endogenous ligand for the estrogen receptor β

Significantly, intraprostatic testosterone levels were not substantially reduced relative to controls with normal serum androgen levels, although DHT levels were reduced to 18% of controls

testosterone levels in many of the CRPC samples were actually increased relative to control tissues (Montgomery et al. 2008). While DHT levels were less markedly increased, this may have reflected DHT catabolism

Approximately 95% of the body's creatine is stored in skeletal muscle

About two thirds of the creatine found in skeletal muscle is stored as phosphocreatine (PCr) while the remaining amount of creatine is stored as free creatine

The body breaks down about 1 – 2% of the creatine pool per day (about 1–2 grams/day) into creatinine in the skeletal muscle

The magnitude of the increase in skeletal muscle creatine content is important because studies have reported performance changes to be correlated to this increase

"loading" protocol. This protocol is characterized by ingesting approximately 0.3 grams/kg/day of CM for 5 – 7 days (e.g., ≃5 grams taken four times per day) and 3–5 grams/day thereafter [18,22]. Research has shown a 10–40% increase in muscle creatine and PCr stores using this protocol

Additional research has reported that the loading protocol may only need to be 2–3 days in length to be beneficial, particularly if the ingestion coincides with protein and/or carbohydrate

A few studies have reported protocols with no loading period to be sufficient for increasing muscle creatine (3 g/d for 28 days)

Cycling protocols involve the consumption of "loading" doses for 3–5 days every 3 to 4 weeks

Most of these forms of creatine have been reported to be no better than traditional CM in terms of increasing strength or performance

Recent studies do suggest, however, that adding β-alanine to CM may produce greater effects than CM alone

These investigations indicate that the combination may have greater effects on strength, lean mass, and body fat percentage; in addition to delaying neuromuscular fatigue

creatine phosphate has been reported to be as effective as CM at improving LBM and strength

Green et al. [24] reported that adding 93 g of carbohydrate to 5 g of CM increased total muscle creatine by 60%

Steenge et al. [23] reported that adding 47 g of carbohydrate and 50 g of protein to CM was as effective at promoting muscle retention of creatine as adding 96 g of carbohydrate.

It appears that combining CM with carbohydrate or carbohydrate and protein produces optimal results

Studies suggest that increasing skeletal muscle creatine uptake may enhance the benefits of training

Nearly 70% of these studies have reported a significant improvement in exercise capacity,

Long-term CM supplementation appears to enhance the overall quality of training, leading to 5 to 15% greater gains in strength and performance

Nearly all studies indicate that "proper" CM supplementation increases body mass by about 1 to 2 kg in the first week of loading

short-term adaptations reported from CM supplementation include increased cycling power, total work performed on the bench press and jump squat, as well as improved sport performance in sprinting, swimming, and soccer

Long-term adaptations when combining CM supplementation with training include increased muscle creatine and PCr content, lean body mass, strength, sprint performance, power, rate of force development, and muscle diameter

subjects taking CM typically gain about twice as much body mass and/or fat free mass (i.e., an extra 2 to 4 pounds of muscle mass during 4 to 12 weeks of training) than subjects taking a placebo

The gains in muscle mass appear to be a result of an improved ability to perform high-intensity exercise via increased PCr availability and enhanced ATP synthesis, thereby enabling an athlete to train harder

there is no evidence to support the notion that normal creatine intakes (< 25 g/d) in healthy adults cause renal dysfunction

no long-term side effects have been observed in athletes (up to 5 years),

One cohort of patients taking 1.5 – 3 grams/day of CM has been monitored since 1981 with no significant side effects

testosterone therapy causes a shift in the skeletal muscle of CHF patients toward a higher concentration of type I muscle fibers

Testosterone replacement therapy has also been shown to improve the homeostatic model of insulin resistance and hemoglobin A1c in diabetics26,68–69 and to lower the BMI in obese patients.

Lower levels of endogenous testosterone have been associated with longer duration of the QTc interval

testosterone replacement has been shown to shorten the QTc interval

negative correlation has been demonstrated between endogenous testosterone levels and IMT of the carotid arteries, abdominal aorta, and thoracic aorta

These findings suggest that men with lower levels of endogenous testosterone may be at a higher risk of developing atherosclerosis.

Current guidelines from the Endocrine Society make no recommendations on whether patients with heart disease should be screened for hypogonadism and do not recommend supplementing patients with heart disease to improve survival.

The Massachusetts Male Aging Study also projects ≈481 000 new cases of hypogonadism annually in US men within the same age group

since 1993 prescriptions for testosterone, regardless of the formulation, have increased nearly 500%

Testosterone levels are lower in patients with chronic illnesses such as end‐stage renal disease, human immunodeficiency virus, chronic obstructive pulmonary disease, type 2 diabetes mellitus (T2DM), obesity, and several genetic conditions such as Klinefelter syndrome

A growing body of evidence suggests that men with lower levels of endogenous testosterone are more prone to develop CAD during their lifetimes

There are 2 major potential confounding factors that the older studies generally failed to account for. These factors are the subfraction of testosterone used to perform the analysis and the method used to account for subclinical CAD.

The biologically inactive form of testosterone is tightly bound to SHBG and is therefore unable to bind to androgen receptors

The biologically inactive fraction of testosterone comprises nearly 68% of the total testosterone in human serum

The biologically active subfraction of testosterone, also referred to as bioavailable testosterone, is either loosely bound to albumin or circulates freely in the blood, the latter referred to as free testosterone

It is estimated that ≈30% of total serum testosterone is bound to albumin, whereas the remaining 1% to 3% circulates as free testosterone

it can be argued that using the biologically active form of testosterone to evaluate the association with CAD will produce the most reliable results

English et al14 found statistically significant lower levels of bioavailable testosterone, free testosterone, and free androgen index in patients with catheterization‐proven CAD compared with controls with normal coronary arteries

patients with catheterization‐proven CAD had statistically significant lower levels of bioavailable testosterone

In conclusion, existing evidence suggests that men with CAD have lower levels of endogenous testosterone,13–18 and more specifically lower levels of bioavailable testosterone

low testosterone levels are associated with risk factors for CAD such as T2DM25–26 and obesity

In a meta‐analysis of these 7 population‐based studies, Araujo et al41 showed a trend toward increased cardiovascular mortality associated with lower levels of total testosterone, but statistical significance was not achieved (RR, 1.25

the authors showed that a decrease of 2.1 standard deviations in levels of total testosterone was associated with a 25% increase in the risk of cardiovascular mortality

the relative risk of all‐cause mortality in men with lower levels of total testosterone was calculated to be 1.35

higher risk of cardiovascular mortality is associated with lower levels of bioavailable testosterone

Existing evidence seems to suggest that lower levels of endogenous testosterone are associated with higher rates of all‐cause mortality and cardiovascular mortality

studies have shown that lower levels of endogenous bioavailable testosterone are associated with higher rates of all‐cause and cardiovascular mortality

It may be possible that using bioavailable testosterone to perform mortality analysis will yield more accurate results because it prevents the biologically inactive subfraction of testosterone from playing a potential confounding role in the analysis

The earliest published material on this matter dates to the late 1930s

the concept that testosterone replacement therapy improves angina has yet to be proven wrong

In more recent studies, 3 randomized, placebo‐controlled trials demonstrated that administration of testosterone improves myocardial ischemia in men with CAD

The improvement in myocardial ischemia was shown to occur in response to both acute and chronic testosterone therapy and seemed to be independent of whether an intravenous or transdermal formulation of testosterone was used.

testosterone had no effect on endothelial nitric oxide activity

There is growing evidence from in vivo animal models and in vitro models that testosterone induces coronary vasodilation by modulating the activity of ion channels, such as potassium and calcium channels, on the surface of vascular smooth muscle cells

Experimental studies suggest that the most likely mechanism of action for testosterone on vascular smooth muscle cells is via modulation of action of non‐ATP‐sensitive potassium ion channels, calcium‐activated potassium ion channels, voltage‐sensitive potassium ion channels, and finally L‐type calcium ion channels

Corona et al confirmed those results by demonstrating that not only total testosterone levels are lower among diabetics, but also the levels of free testosterone and SHBG are lower in diabetic patients

Laaksonen et al65 followed 702 Finnish men for 11 years and demonstrated that men in the lowest quartile of total testosterone, free testosterone, and SHBG were more likely to develop T2DM and metabolic syndrome.

Vikan et al followed 1454 Swedish men for 11 years and discovered that men in the highest quartile of total testosterone were significantly less likely to develop T2DM

authors demonstrated a statistically significant increase in the incidence of T2DM in subjects receiving gonadotropin‐releasing hormone antagonist therapy. In addition, a significant increase in the rate of myocardial infarction, stroke, sudden cardiac death, and development of cardiovascular disease was noted in patients receiving antiandrogen therapy.67

Several authors have demonstrated that the administration of testosterone in diabetic men improves the homeostatic model of insulin resistance, hemoglobin A1c, and fasting plasma glucose

Existing evidence strongly suggests that the levels of total and free testosterone are lower among diabetic patients compared with those in nondiabetics

insulin seems to be acting as a stimulant for the hypothalamus to secret gonadotropin‐releasing hormone, which consequently results in increased testosterone production. It can be argued that decreased stimulation of the hypothalamus in diabetics secondary to insulin deficiency could result in hypogonadotropic hypogonadism

BMI has been shown to be inversely associated with testosterone levels

This interaction may be a result of the promotion of lipolysis in abdominal adipose tissue by testosterone, which may in turn cause reduced abdominal adiposity. On the other hand, given that adipose tissue has a higher concentration of the enzyme aromatase, it could be that increased adipose tissue results in more testosterone being converted to estrogen, thereby causing hypogonadism. Third, increased abdominal obesity may cause reduced testosterone secretion by negatively affecting the hypothalamus‐pituitary‐testicular axis. Finally, testosterone may be the key factor in activating the enzyme 11‐hydroxysteroid dehydrogenase in adipose tissue, which transforms glucocorticoids into their inactive form.

increasing age may alter the association between testosterone and CRP. Another possible explanation for the association between testosterone level and CRP is central obesity and waist circumference

Bai et al have provided convincing evidence that testosterone might be able to shorten the QTc interval by augmenting the activity of slowly activating delayed rectifier potassium channels while simultaneously slowing the activity of L‐type calcium channels

consistent evidence that supplemental testosterone shortens the QTc interval.

Intima‐media thickness (IMT) of the carotid artery is considered a marker for preclinical atherosclerosis

Studies have shown that levels of endogenous testosterone are inversely associated with IMT of the carotid artery,126–128,32,129–130 as well as both the thoracic134 and the abdominal aorta

1 study has demonstrated that lower levels of free testosterone are associated with accelerated progression of carotid artery IMT

another study has reported that decreased levels of total and bioavailable testosterone are associated with progression of atherosclerosis in the abdominal aorta

These findings suggest that normal physiologic testosterone levels may help to protect men from the development of atherosclerosis

Czesla et al successfully demonstrated that the muscle specimens that were exposed to metenolone had a significant shift in their composition toward type I muscle fibers

Type I muscle fibers, also known as slow‐twitch or oxidative fibers, are associated with enhanced strength and physical capability

It has been shown that those with advanced CHF have a higher percentage of type II muscle fibers, based on muscle biopsy

Studies have shown that men with CHF suffer from reduced levels of total and free testosterone.137 It has also been shown that reduced testosterone levels in men with CHF portends a poor prognosis and is associated with increased CHF mortality.138 Reduced testosterone has also been shown to correlate negatively with exercise capacity in CHF patients.

Testosterone replacement therapy has been shown to significantly improve exercise capacity, without affecting LVEF

the results of the 3 meta‐analyses seem to indicate that testosterone replacement therapy does not cause an increase in the rate of adverse cardiovascular events

Data from 3 meta‐analyses seem to contradict the commonly held belief that testosterone administration may increase the risk of developing prostate cancer

One meta‐analysis reported an increase in all prostate‐related adverse events with testosterone administration.146 However, when each prostate‐related event, including prostate cancer and a rise in PSA, was analyzed separately, no differences were observed between the testosterone group and the placebo group

the existing data from the 3 meta‐analyses seem to indicate that testosterone replacement therapy does not increase the risk of adverse cardiovascular events

the authors correctly point out the weaknesses of their study which include retrospective study design and lack of randomization, small sample size at extremes of follow‐up, lack of outcome validation by chart review and poor generalizability of the results given that only male veterans with CAD were included in this study

the studies that failed to find an association between testosterone and CRP used an older population group

low testosterone may influence the severity of CAD by adversely affecting the mediators of the inflammatory response such as high‐sensitivity C‐reactive protein, interleukin‐6, and tumor necrosis factor–α

dietary supplementation of aged mice with the probiotic bacterium Lactobacillus reuteri makes them appear to be younger than their matched untreated sibling mice

These results indicate that gut microbiota induce modulation of local gastrointestinal immunity resulting in systemic effects on the immune system which activate metabolic pathways that restore tissue homeostasis and overall health

all these studies we consistently observed that young and aged mice consuming purified L. reuteri organisms had particularly large testes and a dominant male behavior.

The testes of probiotic-fed aged mice were rescued from both seminiferous tubule atrophy and interstitial Leydig cell area reduction typical of the normal aging process. Preservation of testicular architecture despite advanced age or high-fat diet coincided with remarkably high levels of circulating testosterone. The beneficial effects of probiotic consumption were recapitulated by the depletion of the pro-inflammatory cytokine Il-17.

feeding of L. reuteri consistently increased the gonadal weights, consumption of a non-pathogenic strain of Escherichia coli (E. coli) K12 organisms did not affect testicular weight

mice with dietary L. reuteri supplements were rescued from diet-induced obesity and had normal body weight and lean physique

Despite the comparable numbers of ST profiles, we determined that testes from L. reuteri-treated mice had increased ST cross-sectioned profiles

the probiotic organism induced prominent Leydig cell accumulations in the interstitial tissue between the ST's

The probiotic-associated increase of interstitial Leydig cell areas was sustained with advancing age at 7 (CD vs CD+LR, P = 0.0025; CD+E.coli vs CD+LR, P = 0.0251) and 12 months

mice eating L. reuteri had profoundly increased levels of circulating testosterone regardless of the type of diet they consumed

blocking pro-inflammatory Il-17 signaling entirely recapitulates the beneficial effects of probiotics

previous studies we found that dietary probiotics counteract obesity [19] and age-related integumentary pathology [18] at least in part by down-regulating systemic pro-inflammatory IL-17A-dependent signaling

Testes histomorphometry and serum androgen concentration data were both suggestive of a probiotic-associated up-regulation of spermatogenesis in mice

Lactobacillus reuteri we discovered that aging male animals had larger testes compared to their age-matched controls

xamined testes of probiotic microbe-fed mice and found that they had less testicular atrophy coinciding with higher levels of circulating testosterone compared to their age-matched controls

Similar testicular health benefits were produced using systemic depletion of the pro-inflammatory cytokine Il-17 alone, implicating a chronic inflammatory pathway in hypogonadism

One specific aspect of this paradigm is reciprocal activities of pro-inflammatory Th-17 and anti-inflammatory Treg cells

Feeding of L. reuteri organisms was previously shown to up-regulate IL-10 levels and reduce levels of IL-17 [19] serving to lower systemic inflammation

insufficient levels of IL-10 may increase the risk for autoimmunity, obesity, and other inflammatory disease syndromes

Westernized diets are also low in vitamin D, a nutrient that when present normally works together with IL-10 to protect against inflammatory disorders

Physiological feedback loops apparently exist between microbes, host hormones, and immunity

The hormone testosterone has been shown to act directly through androgen receptors on CD4+ cells to increase IL-10 expression

studies in both humans and rodents suggest that hypogonadism is due to age-related lesions in testes rather than irregular LH metabolism

We postulate that probiotic gut microbes function symbiotically with their mammalian hosts to impart immune homeostasis to maintain systemic and testicular health [34]–[35] despite suboptimal dietary conditions.

Dietary factors and diet-induced obesity were previously shown to increase risk for age-associated male hypogonadism, reduced spermatogenesis, and low testosterone production in both humans and mice [2]–[4], [8]–[11], [14]–[17], phenotypic features that in this study were inhibited by oral probiotic therapy absent milk sugars, extra protein, or vitamin D supplied in yogurt.

Similar beneficial effects of probiotic microbes on testosterone levels and sperm indices were reported in male mice that had been simultaneously supplemented with selenium

L. reuteri-associated prevention of age- and diet-related testicular atrophy correlates with increased numbers and size of Leydig cells

the initial changes of testicular atrophy begin to occur in mice from the age of 6 moths onwards [7] and indicates that the trophic effect of L. reuteri on Leydig cells is a key event which precedes and prevents age-related changes in the testes of mice. This effect is reminiscent of earlier studies describing Leydig cell hyperplasia and/or hypertrophy in the mouse and the rat testis that were achievable by the administration of gonadotropins, including human chorionic gonadotropin, FSH and LH