Definition Erectile dysfunction (ED) is the persistent inability of the penis to achieve or maintain an erection sufficient for satisfactory sexual intercourse for more than three months. Traditional medicine defines penile erectile dysfunction as “impotence” in traditional Chinese medicine. Impotence is caused by the failure of the life-giving fire, deficiency of liver and kidney, or by fright, depression, stagnation of qi and blood, etc. It is an impotence disease with the main manifestation of the inability to complete sexual intercourse due to the inability of the penis to lift, lift but not firm or firm but not long. The etiology and risk factors of penile erectile dysfunction ED is complex and usually the result of multiple factors. The erection of the penis is a complex vascular activity under neuroendocrine regulation, this activity requires the close collaboration of neurological, endocrine, vascular, penile corpus cavernosum and psychological factors, and is affected by systemic diseases, nutrition and drugs, etc., any of these abnormalities may lead to ED. I. Psychosomatic etiology Many domestic and foreign literature reported that psychosomatic disorders can lead to ED. psychological stress is closely related to ED. ED closely related, such as daily couple relationship incompatibility, lack of sexual knowledge, bad sexual experience, work or economic pressure, incorrect understanding of media campaigns, fear of disease and prescription drug side effects caused by anxiety and depression psychological disorders and environmental factors. Likewise, erectile dysfunction as a psychological factor can cause depression, anxiety and somatic symptoms. Experimental studies in rats have shown that sympathetic nervous system hyperexcitability during anxiety is an important cause of psychogenic ED. It has been reported that psychogenic ED may not be a purely functional disorder, and that the hypothalamus may be involved in the pathophysiology of psychogenic ED, and that there may be unrecognized underlying etiological and pathophysiological mechanisms of psychogenic ED. Psychiatric diseases are also one of the common causes of ED, such as schizophrenia patients, the incidence of ED can be as high as 16%-78%, the causes are complex and diverse, the severity of the patient’s psychiatric symptoms and sexual dysfunction are positively correlated. The incidence of endocrine ED in patients with erectile dysfunction with abnormal serum sex hormones is reported to be 16.1%. (A) hypogonadism: male gonads (testes) secrete testosterone, an important factor in normal penile erection, and any disorder that results in lower blood testosterone levels almost inevitably impairs erectile function. Patients with primary hypogonadism have lesions in the testes and have reduced serum testosterone with elevated serum LH or/and FSH, hence the name hypergonadotrophic hypogonadism. Most of these patients have severe irreversible impairment of testicular function. Congenital factors include Crohn’s syndrome and bilateral anencephaly; acquired factors include gonadal injury and systemic diseases. In secondary hypogonadism, the lesion is located in the hypothalamus or pituitary gland, and serum LH, FSH and testosterone are reduced, also known as hypogonadotropic hypogonadism. Congenital factors include selective GnRH deficiency, selective LH deficiency, congenital gonadotropin syndrome; acquired factors include injury (trauma, infarct disease, tumor, surgery, radiotherapy, etc.), excess exogenous or endogenous hormones (androgens, estrogens, glucocorticoids, growth hormone, thyroxine), hyperprolactinemia (idiopathic, pharmacologic, tumor), etc. Reduced synthesis or impaired action of androgens: Several rare genetic disorders reduce testosterone synthesis due to enzyme deficiencies, resulting in genital malformations at birth or inadequate masculinization. 5α-reductase abnormalities or lack of androgen receptors cause androgen insensitivity. Clinical manifestations of androgen insensitivity syndrome can range from infertility to hermaphroditism. (b) Thyroid disease: Abnormal thyroxine can alter hypothalamic-pituitary-gonadal axis function and cause ED. increased secretion of estradiol and reduced clearance of its metabolites in hyperthyroid patients results in elevated serum estradiol levels and diminished testosterone response to hCG. Hypoactive sexual desire in hyperthyroid patients may be related to the hypermetabolic effect of thyroxine and the inhibition of interstitial cell function due to elevated circulating estradiol. In addition, ED can also occur in hypothyroid patients, who have reduced serum testosterone levels. ED can also occur in primary hypothyroidism with increased serum prolactin. (C) other endocrine disorders: acromegaly with elevated serum growth hormone levels, 50% of patients with decreased libido and erectile function, their blood LH is reduced, LH response to GnRH is reduced, suggesting hypothalamic-pituitary insufficiency. Elevated serum prolactin in patients with acromegaly may partially explain their hypogonadism. Cushing syndrome patients with elevated serum cortisol levels, inhibit LH secretion, so that serum testosterone levels decline, can also cause secondary hypogonadism and ED. Third, metabolic causes Metabolic diseases leading to ED, diabetes is most common, the incidence of up to 30%-70%, 2-5 times higher than non-diabetic patients. The incidence of ED increases significantly with the age of diabetic patients and the prolongation of the disease. Because of the complex pathophysiological changes caused by diabetes, including neurovascular and other multifaceted factors, but in essence, the initiating factor may still be endocrine factors. In patients with diabetes, varying degrees of functional, organic or neurotransmitter alterations of the autonomic and somatic nerves as well as peripheral nerves can occur. Diabetes can also cause abnormalities in the white membrane of the penile corpus cavernosum, mainly manifested by increased thickness of the envelope, loss of the wave-like structure of collagen, and a large number of proliferating collagen fibers between the corpus cavernosum and smooth muscle resulting in decreased compliance of the corpus cavernosum, i.e., impaired cavernous diastolic function. Abnormal lipid metabolism is also an important risk factor for ED, and the mechanism is not conclusive. It may involve changes in vascular structure and function, endothelial cells, smooth muscle and nerves, etc. Hyperlipidemia is more closely associated with ED in men over 40 years of age. Most studies have concluded that dyslipidemia affects penile arterial blood flow in two main ways: first, it leads to atherosclerosis of large blood vessels such as the internal iliac artery, internal pubic artery and penile artery, which reduces the blood flow in penile arteries; second, it damages the endothelial cells of blood vessels and affects the relaxation of vascular smooth muscle during penile erection. Fourth, vascular etiology Normal vascular function is the basis for physiological erection of the penis. Vascular lesions are the main cause of ED, accounting for nearly 50% of ED patients, and with the increase in male age incidence has a significant trend of increasing. Arterial ED is one of the common causes of ED in men over the age of 40. Arterial causes of ED include any disease that may lead to reduced blood flow in the cavernous arteries of the penis, such as: atherosclerosis, arterial injury, arterial stenosis, pubic artery shunts, and abnormal cardiac function. Hypertension and the development of erectile dysfunction share common risk factors. Almost all risk factors that can lead to hypertension, such as smoking, hyperlipidemia, and obesity, can increase the incidence of ED. The incidence of venous ED is also high, accounting for approximately 25-78% of ED patients, including venous leakage due to reduced smooth muscle in the penile white membranes and cavernous sinuses. Common causes of venous lesions include congenital venous dysplasia, impaired valve function from various causes (venous degeneration in the elderly, smoking, trauma, and diabetes may cause occlusive dysfunction after venous damage), thinning of the cavernous white membrane, abnormal venous traffic branches, and abnormal shunts caused by surgical treatment of abnormal penile erections. Clinical and morphological data suggest that venous leakage increases with age. V. Neurological diseases Due to the brain, spinal cord, cavernous nerve, pubic nerve and nerve endings, small arteries and receptors on the cavernous body lesions can cause ED, due to the different sites of injury, their pathophysiological mechanisms are also different. (a) central nervous system diseases: brain diseases such as cerebrovascular accidents, Parkinson’s disease, tumors, epilepsy, senile dementia and organic psychosis may cause hypothalamic central dysfunction, or spinal cord central oversuppression and cause ED. spinal cord and many diseases of the central nervous system often complicate ED, ED is only one of a wide range of lesions in the central nervous system due to a variety of dysfunction, these functional abnormalities through Diseases at the spinal cord level such as spina bifida, herniated discs, spinal cavitation, tumors and multiple sclerosis can affect afferent and efferent nerve pathways, resulting in dysfunction. (B) spinal cord injury: ED caused by spinal cord injury depends on the degree of injury and the site of injury. After complete injury to the upper spinal cord, 95% of patients have the ability to erect (reflex erection); while patients with complete injury to the lower spinal cord, only 25% can retain erectile function (psychological erection); however, if the injury is incomplete, more than 90% of patients in both groups preserve the ability to erect. It is now believed that the sympathetic pathway in the thoracolumbar segment may transmit the impulse for psychogenic erection, and since only 25% of patients with complete injury to the lower spinal cord obtain erection through the sympathetic pathway, it is clear that the parasympathetic neurons in the sacral segment are the most important erectile center. (iii) Peripheral nerve injury or lesion: pelvic fracture, surgery on colorectal, bladder, prostate and other organs may damage the cavernous nerve or pubic nerve, disrupting the nerve pathway and causing erectile dysfunction. Peripheral neuropathy such as diabetes, chronic alcoholism, and vitamin deficiency can also cause lesions of the nerves, which may affect the cavernous nerve endings and cause a lack of neurotransmitters. Sensory erectile dysfunction caused by somatosensory nerve damage can have normal nocturnal erections and start with a normal response to sexual stimulation, but cannot maintain a firm erection. In contrast, autonomic erectile dysfunction caused by parasympathetic nerve damage is impaired in all types of erections. Six, drug etiology In recent years, the understanding of drugs leading to ED has gradually improved, but the mechanism is not yet clear. Some of the drugs that may cause ED are shown in Table 1. Seven, other causes of penile anatomy or structural abnormalities, such as small penis, penile curvature, etc. may lead to ED. tumor patients often due to anxiety, depression or tumors accompanied by pain, fever and other symptoms, as well as some tumors can secrete hormones and thus affect endocrine metabolism leading to ED. chronic renal insufficiency can lead to hypogonadism leading to ED. primary varicocele is likely to be The secondary psychological factors of erectile dysfunction can also be one of the psychological causes of erectile dysfunction. Obstructive sleep apnea hypoventilation syndrome (OSAHS) further causes intermittent hypoxemia and sleep fragmentation, which can lead to long-term damage to several target organs of the body, such as hypertension, ischemic heart disease, and stroke. And these are also risk factors for ED, suggesting a possible link between the two in terms of pathogenesis. There are 121 cases of penile erectile dysfunction reported in China after vasectomy, and it is believed that most of them are psychological ED. Eight, mixed etiology Usually, ED is a manifestation of different pathological processes of multiple diseases, that is, ED can be caused by one or more diseases and other factors. Commonly, such as diabetes, hypertension, cardiovascular disease, trauma, surgical injuries and other primary diseases, as well as psychiatric, drug, lifestyle and social and environmental factors. Various diseases and pathogenic factors lead to the occurrence of ED through their different or common pathways. Nine, ED risk factors ED and male ageing is closely related to the United States epidemiological surveys show that the prevalence of less than 40 years old is only 1%-9%, while the prevalence of 60-69 years old increased to 20%-40%, when the age increased to 79-80 years old, the prevalence of up to 50%-75%. The lifestyle of smoking, alcoholism, lack of exercise, irregular sex life, as well as obesity, atherosclerosis, diabetes, hypertension and dyslipidemia metabolic diseases, depression, lower urinary tract symptoms (LUTS), benign prostatic hyperplasia (BPH), etc. are important factors that influence the early and severe occurrence of the disease. Many medications used to treat hypertension and psychiatric disorders are also capable of causing ED.