Sexuality and erection are controlled by multiple areas of the human brain including the hypothalamus, the limbic system, and the cerebral cortex. Stimulatory or inhibitory messages are relayed to the spinal erection centers to facilitate or inhibit erection (5). Two mechanisms have been proposed to explain the inhibition of erection in psychogenic dysfunction: direct inhibition of the spinal erection center by the brain as an exaggeration of the normal suprasacral inhibition and excessive sympathetic outflow or elevated peripheral catecholamine levels, which may increase penile smooth muscle tone and prevent the relaxation necessary for erection (8). Animal studies demonstrate that the stimulation of sympathetic nerves or systemic infusion of epinephrine causes detumescence of the erect penis (6,7). Clinically, higher levels of serum norepinephrine have been reported in patients with psychogenic ED than in normal controls or patients with vasculogenic ED (9).
Neelima V. Chu, MD, is an endocrinology fellow in the Division of Endocrinology and Metabolism at the University of California, San Diego. Steven V. Edelman, MD, is an associate professor of medicine in the Division of Endocrinology and Metabolism at the University of California, San Diego, and the Division of Endocrinology and Metabolism at the San Diego VA Health Care Systems in San Diego. He is founder and director of Taking Control of Your Diabetes, a nonprofit organization, and an associate editor of Clinical Diabetes.
As blood flows into the penis, the corpora cavernosa swell, and this swelling compresses the veins (blood vessels that drain the blood out of the penis) against the tunica albuginea. Compression of the veins prevents blood from leaving the penis. This creates a hard erection. When the amount of cGMP decreases by the action of a chemical called phosphodiesterase type 5 (PDE5), the muscles in the penis tighten, and the blood flow into the penis decreases. With less blood coming into the penis, the veins are not compressed, allowing blood to drain out of the penis, and the erection goes down.
Studies show that high cholesterol and obesity are linked to erectile dysfunction, and both can be improved through diet. "A heart-healthy diet that prevents cardiovascular disease and maintains a healthy weight is also good for erectile functioning," says Feloney. An ideal diet plan involves eating foods low in saturated fat and cholesterol and having frequent servings of fruits, vegetables, and plenty of whole grains.
With coronary artery disease, a buildup of plaque inside the arteries can limit the amount of blood that’s able to flow through them. If the flow of oxygen-rich blood to your heart muscle is reduced or blocked by this hardening of the arteries, the result can be angina (chest pain) or a heart attack.17 Because the arteries that supply blood to the penis are much smaller than the ones that feed the heart, the problem may show up earlier as having difficulty getting an erection.18
High cholesterol and triglyceride levels increase the risk of cardiovascular disease. Getting your cholesterol and triglyceride levels in an optimal range will help protect your heart and blood vessels. Cholesterol management may include lifestyle interventions (diet and exercise) as well as medications to get your total cholesterol, LDL, HDL, and triglycerides in an optimal range.
This is a 22-year-old man who presents with no medical or surgical history who reports that he has never had a rigid erection in his life. He reports normal libido, penile sensation, orgasm, and ejaculation. The remainder of his history is negative. His physical examination is normal with normal genital exam and secondary sexual characteristics. He reported no significant change in erection with PDE5 inhibitors.
medicines called alpha-blockers such as Hytrin (terazosin
HCl), Flomax (tamsulosin HCl), Cardura (doxazosin
mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl),
 Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin).
Alpha-blockers are sometimes prescribed for prostate
problems or high blood pressure. In some patients, the use
of Sildenafil with alpha-blockers can lead to a drop in blood pressure or to fainting
Cardiovascular diseases: The most common cause of cardiovascular diseases in the United States is atherosclerosis, the narrowing and hardening of arteries that reduces blood flow. Atherosclerosis (a type of vascular disease) typically affects arteries throughout the body; hypertension, high blood cholesterol levels, cigarette smoking, and diabetes mellitus aggravate atherosclerosis. Hardening of the arteries to the penis and pelvic organs, atherosclerosis, causes insufficient blood flow into the penis. There is a close correlation between the severity of atherosclerosis in the coronary arteries and erectile dysfunction. For example, men with more severe coronary artery atherosclerosis (hardening of the arteries in the heart) also tend to have more erectile dysfunction than men with mild or no coronary artery atherosclerosis. Some doctors suggest that men with new onset erectile dysfunction undergo evaluation for silent coronary artery diseases (advanced coronary artery atherosclerosis that has not yet caused angina or heart attacks).

The lab testing obtained for the evaluation of erectile dysfunction may vary with the information obtained on the health history, physical examination, and recent lab testing. A testosterone level is not necessary in all men; however, a physician will order labs to determine a patient's testosterone level if other signs and symptoms of hypogonadism (low testosterone) such as decreased libido, loss of body hair, muscle loss, breast enlargement, osteoporosis, infertility, and decreased penile/testicular size are present.
This initial release of NO causes rapid and short-term increases in penile blood flow and short-term relaxation of the penile smooth muscle, initiating an erection.  The resulting expansion of penile blood vessels and smooth-muscle relaxation allows more blood to flow into the penis. This increased blood flow (shear stress) activates the eNOS in penile blood vessels causing sustained NO release, continued relaxation and full erection.

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In regard to circulation, alcohol causes the blood vessels to dilate, which influences the way the blood moves in and out of the penis. A good blood flow regulates the relaxation and contraction of the penis, so it can get and maintain an erection. Without it, no matter how much you may want it to happen differently, your penis will simply remain flaccid.

The initial step in evaluating ED is a thorough sexual history and physical exam. The history can help in distinguishing between the primary and psychogenic causes. It is important to explore the onset, progression, and duration of the problem. If a man gives a history of “no sexual problems until one night,” the problem is most likely related to performance anxiety, disaffection, or an emotional problem. Aside from these causes, only radical prostatectomy or other overt genital tract trauma causes a sudden loss of male sexual function.
There are two kinds of surgery for ED: one involves implantation of a penile prosthesis; the other attempts vascular reconstruction. Expert opinion about surgical implants has changed during recent years; today, surgery is no longer so widely recommended. There are many less-invasive and less-expensive options, and surgery should be considered only as a last resort.
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