Men are very susceptible to visual stimulation, particularly as children and teenagers. Seeing anything appealing (say, a person or image) activates pathways in the brain that tell nerves in your lower spinal cord to trigger a release of nitric oxide, which relaxes blood vessel walls and floods your penis with blood, making it hard. Nitric oxide is the key chemical here, as you need a mix released from your nerves AND from your blood vessels to get an erection. If the blood vessels, nerves, or both are damaged, it's difficult to get a hard erection. That's why your doctor may well be interested if you're struggling with erections, as it could be a sign of early heart disease or diabetes.
Little is known about the natural history of erectile dysfunction. This includes information on the age of onset, incidence rates stratified by age, progression of the condition, and frequency of spontaneous recovery. There also are very limited data on associated morbidity and functional impairment. To date, the data are predominantly available for whites, with other racial and ethnic populations represented only in smaller numbers that do not permit analysis of these issues as a function of race or ethnicity.
Cosgrove et al reported a higher rate of sexual dysfunction in veterans with posttraumatic stress disorder (PTSD) than in veterans who did not develop this problem.  The domains on the International Index of Erectile Function (IIEF) questionnaire that demonstrated the most change included overall sexual satisfaction and erectile function. [43, 44] Men with PTSD should be evaluated and treated if they have sexual dysfunction.
Aging, liver and kidney problems, and concurrent use of certain medications (such as erythromycin [an antibiotic] and protease inhibitors for HIV) slows the metabolism (breakdown) of sildenafil. Slowed breakdown allows sildenafil to accumulate in the body and potentially may increase the risk of side effects. Therefore, in men over 65 years of age, in men with significant kidney and liver disease, and in men who also are taking medications called protease inhibitors, the doctor will initiate sildenafil at a lower dose (25 mg) to avoid accumulation of sildenafil in the body. A protease inhibitor ritonavir (Norvir) is especially potent in increasing the accumulation of sildenafil, thus men who are taking Norvir should not take sildenafil doses higher than 25 mg and at a frequency of no greater than once in 48 hours. Other medications that may affect the level of sildenafil include erythromycin and ketoconazole.
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.
Years ago, the standard treatment for impotence was an implantable penile prosthesis or long-term psychotherapy. Although physical causes are now more readily diagnosed and treated, individual or marital counseling is still an effective treatment for impotence when emotional factors play a role. Fortunately, other approaches are now available to treat the physical causes of impotence.
Impotence is the inability to get and keep an erection hard enough to have sex. Many men experience difficulties getting an erection when they are tired or stressed. This is normal and it doesn’t require treatment. However, if you encounter problems that persist, you may be suffering with a degree of impotence. Impotence is a very treatable condition and help is available either when you visit your local GP or an online doctor.
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 patient'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.
If you are taking medications (alpha-blockers) for problems with an enlarged prostate, you should discuss your prostate medications with your doctor. Alpha-blockers also can cause lowering of the blood pressure. Thus your doctor will need to carefully watch your blood pressure when you start the PDE5 inhibitor. Common alpha-blockers include doxazosin (Cardura), terazosin (Hytrin), and tamsulosin (Flomax).