Two of the immediate metabolites of testosterone, 5α-DHT and estradiol, are biologically important and can be formed both in the liver and in extrahepatic tissues.[147] Approximately 5 to 7% of testosterone is converted by 5α-reductase into 5α-DHT, with circulating levels of 5α-DHT about 10% of those of testosterone, and approximately 0.3% of testosterone is converted into estradiol by aromatase.[2][147][153][154] 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides),[155] skin, hair follicles, and brain[156] and aromatase is highly expressed in adipose tissue, bone, and the brain.[157][158] As much as 90% of testosterone is converted into 5α-DHT in so-called androgenic tissues with high 5α-reductase expression,[148] and due to the several-fold greater potency of 5α-DHT as an AR agonist relative to testosterone,[159] it has been estimated that the effects of testosterone are potentiated 2- to 3-fold in such tissues.[160]

Surgical intervention for a number of conditions may remove anatomical structures necessary to erection, damage nerves, or impair blood supply.[8] Erectile dysfunction is a common complication of treatments for prostate cancer, including prostatectomy and destruction of the prostate by external beam radiation, although the prostate gland itself is not necessary to achieve an erection. As far as inguinal hernia surgery is concerned, in most cases, and in the absence of postoperative complications, the operative repair can lead to a recovery of the sexual life of people with preoperative sexual dysfunction, while, in most cases, it does not affect people with a preoperative normal sexual life.[13]
Erectile dysfunction may be an unpleasant condition that no one really wants to talk about, failing to acknowledge it won’t make the problem go away. Your best defense against health problems like this is to learn everything you can about it so you can tackle the problem at the root. If you’re ready to stop living in embarrassment about your sexual function, become an advocate for yourself and your own health and talk to your doctor.
"The hope," explained Dr. Swerdloff in a telephone interview, "is this will provide some clarity as to whether testosterone replacement therapy will benefit men in this older age group who clearly have abnormal testosterone and have some symptoms." He added, "We don't know whether it will be beneficial at all the endpoints we are studying, or be beneficial to some and not others. We don't know if the benefits occur at different blood levels that are attained in the individuals."

Oral/buccal (by mouth). The buccal dose comes in a patch that you place above your incisor (canine or "eyetooth"). The medication looks like a tablet but you should not chew or swallow it. The drug is released over 12 hours. This method has fewer harmful side effects on the liver than if the drug is swallowed, but it may cause headaches or cause irritation where you place it.


"One of the reasons erectile dysfunction increases with age is that the diseases that lead to it also increase with age," notes Dr. Feloney. Evaluating the causes of erectile dysfunction starts with your doctor taking a good health history and giving you a physical exam. Common medical issues that can lead to erectile dysfunction include diabetes, high blood pressure, hardening of the arteries, low testosterone, and neurological disease. Talk to your doctor about better managing these health conditions.
Cross-sectional studies have found a positive association between serum testosterone and some measures of cognitive ability in men (Barrett-Connor, Goodman-Gruen et al 1999; Yaffe et al 2002). Longitudinal studies have found that free testosterone levels correlate positively with future cognitive abilities and reduced rate of cognitive decline (Moffat et al 2002) and that, compared with controls, testosterone levels are reduced in men with Alzheimer’s disease at least 10 years prior to diagnosis (Moffat et al 2004). Studies of the effects of induced androgen deficiency in patients with prostate cancer have shown that profoundly lowering testosterone leads to worsening cognitive functions (Almeida et al 2004; Salminen et al 2004) and increased levels of serum amyloid (Gandy et al 2001; Almeida et al 2004), which is central to the pathogenesis of Alzheimer’s disease (Parihar and Hemnani 2004). Furthermore, testosterone reduces amyloid-induced hippocampal neurotoxity in vitro (Pike 2001) as well as exhibiting other neuroprotective effects (Pouliot et al 1996). The epidemiological and experimental data propose a potential role of testosterone in protecting cognitive function and preventing Alzheimer’s disease.
5. Medline Plus. US National Library of Medicine. NIH National Institutes of Health. Drugs that may cause impotence (updated 21 Jan 2015). http://www.nlm.nih.gov/medlineplus/ency/article/004024.htm (accessed Nov 2016). myDr myDr provides comprehensive Australian health and medical information, images and tools covering symptoms, diseases, tests, medicines and treatments, and nutrition and fitness.Related ArticlesImpotence treatmentsIf you have impotence (erectile dysfunction), the treatment your doctor recommends will depend on thErectile dysfunction: visiting your doctorFind out what questions a doctor may ask when discussing erectile dysfunction (ED, or impotenceGum disease linked to erectile dysfunctionAdvanced gum disease (periodontitis) has been linked to an increased risk of erectile dysfunction, wPeyronie's diseasePeyronie’s disease is condition where a band of scar tissue forms in the penis, causing aAdvertisement
This evidence, together with the beneficial effects of testosterone replacement on central obesity and diabetes, raises the question whether testosterone treatment could be beneficial in preventing or treating atherosclerosis. No trial of sufficient size or duration has investigated the effect of testosterone replacement in primary or secondary prevention cardiovascular disease. The absence of such data leads us to examine the relationship of testosterone to other cardiovascular risk factors, such as adverse lipid parameters, blood pressure, endothelial dysfunction, coagulation factors, inflammatory markers and cytokines. This analysis can supply evidence of the likely effects of testosterone on overall cardiovascular risk. This has limitations, however, including the potential for diverging effects of testosterone on the various factors involved and the resultant impossibility of accurately predicting the relative impact of such changes.
Fatherhood decreases testosterone levels in men, suggesting that the emotions and behavior tied to decreased testosterone promote paternal care. In humans and other species that utilize allomaternal care, paternal investment in offspring is beneficial to said offspring's survival because it allows the parental dyad to raise multiple children simultaneously. This increases the reproductive fitness of the parents, because their offspring are more likely to survive and reproduce. Paternal care increases offspring survival due to increased access to higher quality food and reduced physical and immunological threats.[60] This is particularly beneficial for humans since offspring are dependent on parents for extended periods of time and mothers have relatively short inter-birth intervals,[61] While extent of paternal care varies between cultures, higher investment in direct child care has been seen to be correlated with lower average testosterone levels[62] as well as temporary fluctuations. For instance, fluctuation in testosterone levels when a child is in distress has been found to be indicative of fathering styles. If a father's testosterone levels decrease in response to hearing their baby cry, it is an indication of empathizing with the baby. This is associated with increased nurturing behavior and better outcomes for the infant[63].

Several treatments were promoted in the pre-PGE1, pre-prostaglandin era, including yohimbine, trazodone, testosterone, and various herbal remedies. None of these is currently recommended under the updated American Urological Association Guidelines for the Treatment of Erectile Dysfunction.15 Testosterone supplementation is only recommended for men with low testosterone levels.

But if a man with sleep apnea is diagnosed with low testosterone alone, taking the supplemental hormone can worsen sleep apnea. That's why it's crucial for men with low testosterone to get a thorough workup by an endocrinologist so underlying conditions that can cause low testosterone, such as sleep apnea or pituitary-gland tumors, don't go undiagnosed, Dr. Goodman says.


Inside the cell, NOS catalyzes the oxidation of L-arginine to NO and L-citrulline. Endogenous blockers of this pathway have been identified. The gaseous NO that is produced acts as a neurotransmitter or paracrine messenger. Its biologic half-life is only 5 seconds. NO may act within the cell or diffuse and interact with nearby target cells. In the corpora cavernosa, NO activates guanylate cyclase, which in turn increases cyclic guanosine monophosphate (cGMP). Relaxation of vascular smooth muscles by cGMP leads to vasodilation and increased blood flow.
The PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are prescription drugs which are taken orally.[22]:20–21 Additionally, a cream combining alprostadil with the permeation enhancer DDAIP has been approved in Canada as a first line treatment for erectile dysfunction.[25] Penile injections, on the other hand, can involve one of the following medications: papaverine, phentolamine, and prostaglandin E1.[22]:25
There have been case reports of development of prostate cancer in patients during treatment with testosterone, including one case series of twenty patients (Gaylis et al 2005). It is not known whether this reflects an increase in incidence, as prostate cancer is very common and because the monitoring for cancer in patients treated with testosterone is greater. Randomized controlled trials of testosterone treatment have found a low incidence of prostate cancer and they do not provide evidence of a link between testosterone treatment and the development of prostate cancer (Rhoden and Morgentaler 2004). More large scale clinical trials of longer durations of testosterone replacement are required to confirm that testosterone treatment does not cause prostate cancer. Overall, it is not known whether testosterone treatment of aging males with hypogonadism increases the risk of prostate cancer, but monitoring for the condition is clearly vital. This should take the form of PSA blood test and rectal examination every three months for the first year of treatment and yearly thereafter (Nieschlag et al 2005). Age adjusted PSA reference ranges should be used to identify men who require further assessment. The concept of PSA velocity is also important and refers to the rate of increase in PSA per year. Patients with abnormal rectal examination suggestive of prostate cancer, PSA above the age specific reference range or a PSA velocity greater than 0.75 ng/ml/yr should be referred to a urologist for consideration of prostate biopsy.
Men's levels of testosterone, a hormone known to affect men's mating behaviour, changes depending on whether they are exposed to an ovulating or nonovulating woman's body odour. Men who are exposed to scents of ovulating women maintained a stable testosterone level that was higher than the testosterone level of men exposed to nonovulation cues. Testosterone levels and sexual arousal in men are heavily aware of hormone cycles in females.[46] This may be linked to the ovulatory shift hypothesis,[47] where males are adapted to respond to the ovulation cycles of females by sensing when they are most fertile and whereby females look for preferred male mates when they are the most fertile; both actions may be driven by hormones.
It is normal for a man to have five to six erections during sleep, especially during rapid eye movement (REM). Their absence may indicate a problem with nerve function or blood supply in the penis. There are two methods for measuring changes in penile rigidity and circumference during nocturnal erection: snap gauge and strain gauge. A significant proportion of men who have no sexual dysfunction nonetheless do not have regular nocturnal erections.
There is a dirty little secret about testosterone cream that almost no one knows, and I’m going to share it here. Please don’t abuse it. If you take a vanishingly small dose of testosterone cream and apply it to your labia and the vulva (or your partner’s), you will witness a form of vasodilation rarely seen no matter how good you are in bed. It has a profound local effect and will produce a night you won’t forget for years.
This is similar to magnetic resonance imaging. Magnetic resonance angiography uses magnetic fields and radio waves to provide detailed images of the blood vessels. Doctors may inject a "contrast agent" into the person's bloodstream that causes vascular tissues to stand out against other tissues. The contrast agent provides for enhanced information regarding blood supply and vascular anomalies.
The mechanism of age related decreases in serum testosterone levels has also been the subject of investigation. Metabolic clearance declines with age but this effect is less pronounced than a reduction in testosterone production, so the overall effect is to reduce serum testosterone levels. Gonadotrophin levels rise during aging (Feldman et al 2002) and testicular secretory responses to recombinant human chorionic gonadotrophin (hCG) are reduced (Mulligan et al 1999, 2001). This implies that the reduced production may be caused by primary testicular failure but in fact these changes are not adequate to fully explain the fall in testosterone levels. There are changes in the lutenising hormone (LH) production which consist of decreased LH pulse frequency and amplitude, (Veldhuis et al 1992; Pincus et al 1997) although pituitary production of LH in response to pharmacological stimulation with exogenous GnRH analogues is preserved (Mulligan et al 1999). It therefore seems likely that there are changes in endogenous production of GnRH which underlie the changes in LH secretion and have a role in the age related decline in testosterone. Thus the decreases in testosterone levels with aging seem to reflect changes at all levels of the hypothalamic-pituitary-testicular axis. With advancing age there is also a reduction in androgen receptor concentration in some target tissues and this may contribute to the clinical syndrome of LOH (Ono et al 1988; Gallon et al 1989).

Stress is your body responding to your environment. And it’s a good thing—in limited doses. When you get stressed out your body makes chemicals like adrenaline that make you stronger, faster, fitter, and even able to think more clearly. Most people call this reaction the “fight-or-flight” response, and it’s a life-saver in dangerous situations. In a very real sense, adrenaline makes you a part-time superhero. The problems happen when your body deals with constant stress.

Acupuncture may help treat psychological ED, though studies are limited and inconclusive. You’ll likely need several appointments before you begin to notice any improvements. When choosing an acupuncturist, look for a certified practitioner who uses disposable needles and follows U.S. Food and Drug Administration guidelines for needle disposal and sterilization.
Research has even found possible links to frequent ejaculation and a lower risk of prostate cancer. In one study of 32,000 men published in 2016 in the journal European Urology, for example, men who ejaculated at least 21 times per month while in their 20s were less likely to be diagnosed with prostate cancer than those who ejaculated four to seven times per month. And men who ejaculated more often in their 40s were 22 percent less likely to get a prostate cancer diagnosis.
The medications are extremely effective, which is very good. And the medications are, for the most part, extremely well-tolerated. But there are, like with any medications, a potential downside. The one absolute downside to the use of any of these erection what we call PDE5 medications is if a patient is using a nitroglycerin medication. And nitroglycerins are used for heart disease and for angina, for the most part, although there are some recreational uses of nitrites. And that’s important because your blood vessels will dilate and your blood pressure will drop. And that is an absolute contraindication.
You’ve probably heard of Viagra, but it’s not the only pill for ED. This class of drugs also includes Cialis, Levitra,  Staxyn, and Stendra. All work by improving blood flow to the penis during arousal. They're generally taken 30-60 minutes before sexual activity and should not be used more than once a day. Cialis can be taken up to 36 hours before sexual activity and also comes in a lower, daily dose. Staxyn dissolves in the mouth. All require an OK from your doctor first for safety.
It is essential to discuss erectile dysfunction with your doctor, so any serious underlying causes can be excluded and treatment options can be discussed. Many men are embarrassed discussing this issue with their doctor, or even their partner. Open communication with your doctor, and in your relationship, is important for effectively managing this common problem.
A common and important cause of ED is vasculogenic. Many men with ED have comorbid conditions such as hyperlipidemia, hypercholesterolemia, tobacco abuse, diabetes mellitus, or coronary artery disease (CAD). [6] The Princeton III Consensus recommends screening men who present with ED for cardiovascular risk factors; ED may be the earliest presentation of atherosclerosis and vascular disease. [7]
Do erectile dysfunction exercises help? Many people have erectile dysfunction (ED), but it is often possible to reverse this with exercises to strengthen muscles in the area. These include pelvic floor exercises. ED can often be due to lifestyle factors including obesity and low physical activity levels. Learn more about exercises for ED here. Read now
A testicular action was linked to circulating blood fractions – now understood to be a family of androgenic hormones – in the early work on castration and testicular transplantation in fowl by Arnold Adolph Berthold (1803–1861).[174] Research on the action of testosterone received a brief boost in 1889, when the Harvard professor Charles-Édouard Brown-Séquard (1817–1894), then in Paris, self-injected subcutaneously a "rejuvenating elixir" consisting of an extract of dog and guinea pig testicle. He reported in The Lancet that his vigor and feeling of well-being were markedly restored but the effects were transient,[175] and Brown-Séquard's hopes for the compound were dashed. Suffering the ridicule of his colleagues, he abandoned his work on the mechanisms and effects of androgens in human beings.
Hormone deficiency or hypogonadism, whether primary or secondary, has been thought to impact erectile function. Approximately a third of men in the European Male Aging Study demonstrated low testosterone, suggesting that hypogonadism is overrepresented among men with ED.11 Hormone deficiency, however, is less frequently the cause of ED than diabetes or vascular disease. Many entities with a strong relationship to ED also diminish bioavailable testosterone, including obesity, diabetes, and opioid use. Other hormones involved in testosterone metabolism or availability, like thyroid stimulating hormone and gonadotropins, also may impact erectile quality, presumably through regulating bioavailable testosterone. Understanding the relationship between testosterone and ED has been impaired by a lack of standardized measurement of this hormone and the cyclic nature of its release and consumption.
Medications for erectile dysfunction don't work for everyone and may cause side effects that make a particular drug hard to take. "Work with your doctor to find the right treatment. There are still options for people who fail at medical treatment," advises Feloney. Alternatives to erectile dysfunction drugs include vacuum pump devices, medications injected into the penis, testosterone replacement if needed, and a surgical penile implant.
When Solvay Pharmaceuticals, maker of market-dominating Androgel, launched its "Low T" campaign, in 2008, it claimed that 13 million American men over age 45 suffered from low testosterone, 90 percent of them undiagnosed. Its website, IsItLowT.com, showed dumpy, depressed men and their unhappy spouses remembering how it "used to be." Why settle for dumpiness and depression, the website and related TV ads suggested, when a little dab'll do you?

NO is produced by the enzyme NO synthase (NOS). [13] NOS plays many roles, ranging from homeostasis to immune system regulation. To date, 3 subtypes have been identified: nNOS, iNOS, and eNOS, which are produced by the genes NOS1, NOS2, and NOS3, respectively. This nomenclature is derived from the sources of the original isolates: neuronal tissue (nNOS), immunoactivated macrophage cell lines (iNOS), and vascular endothelium (eNOS). The subtypes are not, however, limited to the tissues from which they were first isolated.
The changes in average serum testosterone levels with aging mean that the proportion of men fulfilling a biochemically defined diagnosis of hypogonadism increases with aging. Twenty percent of men aged over 60 have total testosterone levels below the normal range and the figure rises to 50% in those aged over 80. The figures concerning free testosterone are even higher as would be expected in view of the concurrent decrease in SHBG levels (Harman et al 2001).
"One of the reasons erectile dysfunction increases with age is that the diseases that lead to it also increase with age," notes Dr. Feloney. Evaluating the causes of erectile dysfunction starts with your doctor taking a good health history and giving you a physical exam. Common medical issues that can lead to erectile dysfunction include diabetes, high blood pressure, hardening of the arteries, low testosterone, and neurological disease. Talk to your doctor about better managing these health conditions.
When females have a higher baseline level of testosterone, they have higher increases in sexual arousal levels but smaller increases in testosterone, indicating a ceiling effect on testosterone levels in females. Sexual thoughts also change the level of testosterone but not level of cortisol in the female body, and hormonal contraceptives may affect the variation in testosterone response to sexual thoughts.[51]
At the present time, it is suggested that androgen replacement should take the form of natural testosterone. Some of the effects of testosterone are mediated after conversion to estrogen or dihydrotestosterone by the enzymes aromatase and 5a-reductase enzymes respectively. Other effects occur independently of the traditional action of testosterone via the classical androgen receptor- for example, its action as a vasodilator via a cell membrane action as described previously. It is therefore important that the androgen used to treat hypogonadism is amenable to the action of these metabolizing enzymes and can also mediate the non-androgen receptor actions of testosterone. Use of natural testosterone ensures this and reduces the chance of non-testosterone mediated adverse effects. There are now a number of testosterone preparations which can meet these recommendations and the main factor in deciding between them is patient choice.

"One of the reasons erectile dysfunction increases with age is that the diseases that lead to it also increase with age," notes Dr. Feloney. Evaluating the causes of erectile dysfunction starts with your doctor taking a good health history and giving you a physical exam. Common medical issues that can lead to erectile dysfunction include diabetes, high blood pressure, hardening of the arteries, low testosterone, and neurological disease. Talk to your doctor about better managing these health conditions.
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