A larger national study, the National Health and Social Life Survey, looked at sexual function in men and women.4 This study surveyed 1,410 men aged 18 to 59 and also documented an increase in ED with age. Additionally, the study found a decrease in sexual desire with increasing age. Men in the oldest cohort (50 to 59) were more than 3 times as likely to experience erection problems and to report low sexual desire compared with men 18 to 29. Experience of sexual dysfunction was more likely among men in poor physical and emotional health. The study also concluded that sexual dysfunction is an important public health concern and that emotional issues are likely to contribute to the experience sexual dysfunction.
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. 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. 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides), skin, hair follicles, and brain and aromatase is highly expressed in adipose tissue, bone, and the brain. As much as 90% of testosterone is converted into 5α-DHT in so-called androgenic tissues with high 5α-reductase expression, and due to the several-fold greater potency of 5α-DHT as an AR agonist relative to testosterone, it has been estimated that the effects of testosterone are potentiated 2- to 3-fold in such tissues.
Factors that mediate contraction in the penis include noradrenaline, endothelin-1, neuropeptide Y, prostanoids, angiotensin II, and others not yet identified. Factors that mediate relaxation include acetylcholine, nitric oxide (NO), vasoactive intestinal polypeptide, pituitary adenylyl cyclase–activating peptide, calcitonin gene–related peptide, adrenomedullin, adenosine triphosphate, and adenosine prostanoids.
In rare cases, the drug Viagra ® can cause blue-green shading to vision that lasts for a short time. In rare cases, the drug Cialis® can cause or increase back pain or aching muscles in the back. In most cases, the side effects are linked to PDE5 inhibitor effects on other tissues in the body, meaning they are working to increase blood flow to your penis and at the same time impacting other vascular tissues in your body. These are not ‘allergic reactions'.
Unfortunately, some patients may have an overly simplified understanding of the role of PDE5 inhibitors in ED management. Such patients may not expect or be willing to undergo a long evaluation and testing process to obtain a better understanding of their sexual problem, and they may be less likely to involve their partner in discussing their sexual relationship with the physician. They may expect to obtain medications through a phone call to their doctor or even over the Internet, with minimal or no physician contact at all.
Abnormally high levels of testosterone could be the result of an adrenal gland disorder, or even cancer of the testes. High levels may also occur in less serious conditions. Congenital adrenal hyperplasia, which can affect males and females, is a rare but natural cause for elevated testosterone production. Your doctor may order other tests if your levels are exceedingly high.
If you have symptoms of ED, it’s important to check with your doctor before trying any treatments on your own. This is because ED can be a sign of other health problems. For instance, heart disease or high cholesterol could cause ED symptoms. With a diagnosis, your doctor could recommend a number of steps that would likely improve both your heart health and your ED. These steps include lowering your cholesterol, reducing your weight, or taking medications to unclog your blood vessels.
Male hypogonadism is a clinical syndrome caused by a lack of androgens or their action. Causes of hypogonadism may reflect abnormalities of the hypothalamus, pituitary, testes or target tissues. Increases in the amount of testosterone converted to estrogen under the action of the enzyme aromatase may also contribute to hypogonadism. Most aspects of the clinical syndrome are unrelated to the location of the cause. A greater factor in the production of a clinical syndrome is the age of onset. The development of hypogonadism with aging is known as late-onset hypogonadism and is characterised by loss of vitality, fatigue, loss of libido, erectile dysfunction, somnolence, depression and poor concentration. Hypogonadal ageing men also gain fat mass and lose bone mass, muscle mass and strength.
The nerves and endothelium of sinusoids and vessels in the penis produce and release transmitters and modulators that control the contractile state of corporal smooth muscles. Although the membrane receptors play an important role, downstream signaling pathways are also important. The RhoA–Rho kinase pathway is involved in the regulation of cavernosal smooth muscle contraction. 
Hacking your testosterone influences everything from body composition to energy levels to mood. It’s easy to eat more butter; it’s hard to visit a doctor and get tested, but that’s what I recommend: know your levels. If you’re 25, you’ll know what your target is when you’re 35. By the time you’ve noticed symptoms of low testosterone, it’s too late to get your “normal” measurements!
Erectile dysfunction - (ED) or impotence is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual activity. A penile erection is the hydraulic effect of blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the penis.
The physical side effects of chemotherapy are usually temporary and resolve within one to two weeks after stopping the chemotherapy. However, chemotherapy agents, such as Ciplatin or Vincristine, may interfere with the nerves that control erection leading to possible impotence. Make sure you discuss potential side effects of cancer chemotherapy with your doctor or healthcare provider.
Erections occur in response to tactile, olfactory, and visual stimuli. The ability to achieve and maintain a full erection depends not only on the penile portion of the process but also on the status of the peripheral nerves, the integrity of the vascular supply, and biochemical events within the corpora. The autonomic nervous system is involved in erection, orgasm, and tumescence. The parasympathetic nervous system is primarily involved in sustaining and maintaining an erection, which is derived from S2-S4 nerve roots.
The dorsal artery provides for engorgement of the glans during erection, whereas the bulbourethral artery supplies the bulb and the corpus spongiosum. The cavernous artery effects tumescence of the corpus cavernosum and thus is principally responsible for erection. The cavernous artery gives off many helicine arteries, which supply the trabecular erectile tissue and the sinusoids. These helicine arteries are contracted and tortuous in the flaccid state and become dilated and straight during erection. 
Dr. Fugh-Berman said these campaigns encourage men to "ask your doctor" whether their weight gain, falling asleep after dinner, reduced energy, and diminished sex drive are due to "Low T." At the same time, the companies are working other angles to influence doctors' prescribing practices through industry-sponsored continuing medical education (CME) courses and sponsored medical journal articles. They have even created a respectable-sounding journal called The Aging Male. Fugh-Berman said all these channels "are being used to persuade doctors they should be treating this."
When a man becomes sexually excited, muscles in their penis relax. This relaxation allows for increased blood flow through the penile arteries. This blood fills two chambers inside the penis called the corpora cavernosa. As the chambers fill with blood, the penis grows rigid. Erection ends when the muscles contract and the accumulated blood can flow out through the penile veins.
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.
"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.