Conditions associated with reduced nerve and endothelium function (eg, aging, hypertension, smoking, hypercholesterolemia, and diabetes) alter the balance between contraction and relaxation factors (see Pathophysiology). These conditions cause circulatory and structural changes in penile tissues, resulting in arterial insufficiency and defective smooth muscle relaxation. In some patients, sexual dysfunction may be the presenting symptom of these disorders.
The primary nerve fibers to the penis are from the dorsal nerve of the penis, a branch of the pudendal nerve. The cavernosal nerves are a part of the autonomic nervous system and incorporate both sympathetic and parasympathetic fibers. They travel posterolaterally along the prostate and enter the corpora cavernosa and corpus spongiosum to regulate blood flow during erection and detumescence. The dorsal somatic nerves are also branches of the pudendal nerves. They are primarily responsible for penile sensation. 
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Although not indicated for routine use, nocturnal penile tumescence (NPT) testing may be useful in the patient who reports a complete absence of erections (exclusive of nocturnal "sleep" erections) or when a primary psychogenic etiology is suspected. Such testing should be performed by those with expertise and knowledge of its interpretation, pitfalls, and usefulness. Various methods and devices are available for the evaluation of nocturnal penile tumescence, but their clinical usefulness is restricted by limitations of diagnostic accuracy and availability of normative data. Further study regarding standardization of NPT testing and its general applicability is indicated.
Parasympathetic input allows erection by relaxation of trabecular smooth muscle and dilation of the helicine arteries of the penis. This leads to expansion of the lacunar spaces and entrapment of blood by compressing venules against the tunica albuginea, a process referred to as the corporal veno-occlusive mechanism. The tunica albuginea must have sufficient stiffness to compress the venules penetrating it so that venous outflow is blocked and sufficient tumescence and rigidity can occur.
Other medical therapies under evaluation include ROCK inhibitors and soluble guanyl cyclase activators. Melanocortin receptor agonists are a new set of medications being developed in the field of erectile dysfunction. Their action is on the nervous system rather than the vascular system. PT-141 is a nasal preparation that appears to be effective alone or in combination with PDE5 inhibitors. The main side effects include flushing and nausea. These drugs are currently not approved for commercial use.
You get to decide what is normal for you. That might include him still experiencing pleasure from you touching his penis even if he’s not hard. Some men can still orgasm without an erection. Or he may prefer not to have any touching while he is dealing with his erection problems. It is okay for you to orgasm even if he doesn’t. Reading about what might bring you pleasure, or considering how you think about sex can make this something enjoyable to explore together.
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Currently, placement of a penile prosthesis is the most common surgical procedure performed for erectile dysfunction. Penile prosthesis placement is typically reserved for men who have tried and failed (either from efficacy or tolerability) or have contraindications to other forms of therapy including PDE5 inhibitors, intraurethral alprostadil, and injection therapy.
While we may think the penis has a mind of it’s own, it’s actually heavily dependent to the brain, and too much stress can interfere with a man’s ability to obtain and hold an erection. According to Healthline, stress can interrupt how your brain sends messages to the penis to allow extra blood flow. Even though a man may want to have sex, too much stress can make this impossible.
The role of the endothelium in ED has been noted for a number of years and the overlapping of ED and other conditions, especially coronary heart disease, CVD, affecting endothelial function/dysfunction, is clearly present. The endothelial cell is now known to affect vascular tone and impact the process of atherosclerosis, and impacting ED, CVD and peripheral vascular disease.16
Chlamydia and erectile dysfunction: What's the link? Some people who have chlamydia also experience erectile dysfunction (ED), which involves problems getting or maintaining an erection. Chlamydia can infect the prostate gland, leading to prostatitis, pain, and ED. In this article, learn more about the link between this common infection and ED, and treatments for both. Read now
Alteration of NO levels is the focus of several approaches to the treatment of ED. Inhibitors of phosphodiesterase, which primarily hydrolyze cGMP type 5, provided the basis for the development of the PDE5 inhibitors. Chen et al administered oral L-arginine and reported subjective improvement in 50 men with ED.  These supplements are readily available commercially. Reported adverse effects include nausea, diarrhea, headache, flushing, numbness, and hypotension.
Recently, the US Food and Drug Administration (FDA) has issued a safety announcement regarding TRT. In part it reads ‘The benefit and safety of these medications have not been established. We are also requiring these manufacturers to add information to the labeling about a possible increased risk of heart attacks and strokes in patients taking testosterone.’37
Aging: There are two reasons why older men are more likely to experience erectile dysfunction than younger men. First, older men are more likely to develop diseases (such as heart attacks, angina, cardiovascular disease, strokes, diabetes mellitus, and high blood pressure) that are associated with erectile dysfunction. Second, the aging process alone can cause erectile dysfunction in some men by causing changes in the muscle and tissue within the penis.