Erectile dysfunction (ED) is one of the most common sexual dysfunctions in men. In 1993, the NIH (National Institute of Health) defined ED as “sexual dysfunction in which the male penis is unable to achieve or maintain a sufficient erection for satisfactory sexual intercourse. “. The incidence of ED in China is estimated to be about 10%. I. Epidemiology of erectile dysfunction The epidemiology of ED focuses on the distribution of ED in the general and special populations and the risk factors for ED. Due to the traditional avoidance of sexual problems, many patients do not go to the doctor or cannot confess their condition, and related research has also started late, resulting in unsatisfactory epidemiological studies of ED. ED risk factors are mainly age, psychological factors, physical diseases, drugs, trauma, surgery and other medical factors and poor lifestyle. 1, age As age increases, in addition to a decrease in libido, erectile function will also change significantly; the sensitivity of the penis will also decline, the penis takes longer to achieve erection; the influence of psychological stimulation on penile erection decreases, penile erection will rely more on physical stimulation; the frequency and duration of penile erection at night will also decrease; at the same time, sexual pleasure during intercourse and ejaculation when the strength and volume of semen will also decline. 2, psychological factors Psychological factors lead to the occurrence of ED through special mechanisms. MMAS study found that: severe mental depression, temper tantrums and strong desire to rule in men, the prevalence of moderate ED were 35%, 35% and 15%; the prevalence of severe ED were 16%, 19% and 7.9%. Organic erectile dysfunction is not effectively treated for a long time, will increase the psychological burden of patients, the latter will make the condition further aggravated, or even transformed into the main aspect of the conflict. 3, somatic diseases With the development of male science and the application of many new treatment techniques, it was found that purely psychological or purely organic erectile dysfunction is rare, the vast majority of both. As organic ED is not timely treatment of patients with increased psychological pressure, fear of failure of sexual intercourse, so that ED treatment tends to be more complex. A group of 628 domestic ED patients etiology classification study showed that: psychological accounted for 39%. Organic is 15.8%, and mixed 45.2%. Erectile dysfunction is mainly related to the following physical diseases: cardiovascular disease itself risk factors such as age, hyperlipidemia, smoking and other risk factors for ED, research suggests that the cardiovascular status of patients should be evaluated before starting treatment for ED, because ED may be a local manifestation of systemic atherosclerosis. Diabetes can lead to systemic vascular and neuropathy, which may cause ED. studies have found that the higher the total serum cholesterol, the lower the HDL, the greater the likelihood of ED. In addition, chronic renal insufficiency, hyperprolactinemia, adrenal gland disease, thyroid disease, penile sclerosis and other physical diseases can lead to ED. 4, drugs Some studies have shown that drug-related ED accounted for 25%, but this information is mostly from clinical experience, case reports, etc., the lack of rigorous evidence-based medical research. 5, trauma, surgery and other medical factors Any injury to the penile innervation, vascular supply and androgen sources of trauma or surgery, including the resulting psychological factors may lead to ED. 6, poor lifestyle Some studies suggest that smoking is an independent risk factor for ED, and may synergize or enhance the role of other risk factors, but the incidence of ED and current or lifetime smoking is not dependent on the relationship. Alcohol consumption can improve desire, but may reduce sexual function. The likelihood of ED is also increased in men with long-term drug use. Second, the physiology of penile erection In essence, the process of penile erection is a series of neurovascular activity, the nerves that control penile erection and relaxation are mainly sympathetic and parasympathetic nerves. When there is no sexual stimulation, sympathetic nerve is the main action, arterial smooth muscle contracts, penile cavernous trabeculae also contract, trabecular space is empty, arterial inflow is obviously reduced and basically balanced with venous outflow, and the penis is in a weak state; when sexual stimulation parasympathetic nerve is the main action, arterial smooth muscle diastole, arterial inflow increases sharply, while penile cavernous trabeculae relax, trabecular space expands, and the penis is in a weak state. Compressing the small submembranous veins, the venous outflow is reduced and the penis erects. Erections are classified as reflex erections, psychogenic erections and nocturnal erections. A reflex erection is an erection produced by sensory stimulation through the pubic nerves and sacral sex centers. Reflex erection is accomplished by nerve reflexes, and the afferent nerves of its reflex arc are the dorsal penile nerve and the perineal nerve, and the efferent nerve is the parasympathetic nerve of the sacral region. Injuries to the spinal cord, spinal nerve roots, pelvic nerve, perineal nerve, and cavernous nerve can lead to the loss of transmitting erection; the effect of spinal cord injury on erectile function is related to the height of the injury; injuries above the thoracic segment of the spinal cord have little effect, while injuries to the following parts can have serious effects and even lead to the loss of reflex erection. Psychogenic erection is an erection of the penis caused by the sexual awareness generated by the brain. Psychogenic erections are synergistic with reflex erections. Psychogenic erections are more common in young people and gradually decrease with age. Nocturnal erection, also known as nocturnal penile tumescene (NPT) is an erection of the penis that occurs during the rapid eye movement phase of sleep. NPT occurs in all healthy men, including infants and older men , and the mechanism of NPT has not been discovered, but most researchers believe it is related to the transmission of information from the central nervous system to the sacral parasympathetic plexus during sleep. The presence or absence of NPT is an important aspect of clinical differentiation between psychological erectile dysfunction and organic erectile dysfunction. In general, penile erectile function decreases with increasing age. As age increases, the penis may require stronger stimulation to achieve an erection, and there is a tendency for the intensity of orgasm and the frequency of sexual intercourse to diminish, as well as a longer interval between erections. However, as age increases, the incidence of various diseases and the use of various drugs increase accordingly, so it is sometimes difficult to distinguish whether the changes in erectile dysfunction are caused by old age or by diseases or drugs. The diagnosis of erectile dysfunction can be diagnosed by taking a detailed medical history, conducting a physical examination and the necessary laboratory tests to diagnose ED. 1, medical history Due to the influence of traditional concepts, ED patients are often difficult to talk about their condition, so the patient should be quiet and comfortable environment, urology or male physicians should seek the trust of patients in order to obtain objective and detailed clinical information. The past history should be reviewed for psychiatric, cardiovascular, endocrine, neurological, and genitourinary systems, with the cardiovascular and endocrine systems being the most important. In addition, the patient’s medication, history of trauma or surgery, and whether the patient smokes and drinks alcohol should be asked. 2. Physical examination The main observations are the patient’s body shape, hair and subcutaneous fat distribution, secondary sexual characteristics and the presence of gynecomastia feminization. Blood pressure and pulses of the extremities, and the presence of hepatosplenomegaly should also be measured. Neurological examinations of the lower abdomen, lower extremities, perineum and penis such as pain and temperature sensation and bulbocavernosal reflexes should be performed. The size and shape of the penis, abnormalities of the foreskin, and careful palpation of the penile corpus cavernosum should be checked; the size and texture of the testicles, the presence of testicular sphingomyelia, varicocele, etc. should be examined; the condition of the prostate should be checked by anal finger diagnosis. The actual test is a good way to find out about diabetes, liver and kidney disorders and hyperlipidemia. In addition, some special tests are still needed.