29.17B: Erectile Dysfunction and the Blue Pill
Erectile dysfunction (ED) is the inability to develop or maintain an erection during sexual intercourse.
- Describe the causes of and treatments for erectile dysfunction
Key Points
- A penile erection is managed by a reflex erection (obtained by touching the penis ) and/or a psychogenic erection (achieved by erotic/emotional stimuli).
- There are many causes of ED, including neurogenic disorders, Parkinson’s disease, aging, drugs, and psychological factors.
- Treatment for ED includes drugs such as Viagra (Sildenafil), Cialis (Tadalifil), exercise, and vacuum therapy.
- Psychological impotence is where erection or penetration fails due to thoughts or feelings (psychological reasons) rather than physical impossibility; this is somewhat less frequent but can often be helped.
- As can be understood from the mechanisms of a normal erection, impotence may develop due to hormonal deficiency, disorders of the neural system, lack of adequate penile blood supply, or psychological problems.
Key Terms
- psychogenic erection : Erection achieved by erotic or emotional stimuli
- chronic periodontitis : Chronic periodontitis is a common disease of the oral cavity consisting of chronic inflammation of the periodontal tissues, often caused by accumulation of profuse amounts of dental plaque.
- Erectile dysfunction : Erectile dysfunction (ED) is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance.
Erectile dysfunction (ED) is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance. A penile erection is the hydraulic effect of blood entering and being retained in sponge-like bodies within the penis. The process is often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the penis. Erectile dysfunction is indicated when an erection is difficult to produce. There are various circulatory causes, including alteration of the voltage-gated potassium channel, as in arsenic poisoning from drinking water. The most significant organic causes are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism), and drug side effects. Psychological impotence is where erection or penetration fails due to thoughts or feelings (psychological reasons) rather than physical impossibility; this is somewhat less frequent but can often be helped. Notably, there is a strong response to placebo treatment in psychological impotence.
Erectile Function
Corpus Cavernosum Urethrae now known as Corpus Spongiosum : The corpus cavernosum penis is one of a pair of sponge-like regions of erectile tissue which contain most of the blood in the penis during penile erection.
Penile erection is managed by two different mechanisms. The first one is the reflex erection, which is achieved by directly touching the penile shaft. The second is the psychogenic erection, which is achieved by erotic or emotional stimuli. The former uses the peripheral nerves and the lower parts of the spinal cord, whereas the latter uses the limbic system of the brain. In both circumstances, an intact neural system is required for a successful and complete erection. Stimulation of penile shaft by the nervous system leads to the secretion of nitric oxide (NO), which causes the relaxation of smooth muscles of corpora cavernosa (the main erectile tissue of penis), and subsequently penile erection. Additionally, adequate levels of testosterone (produced by the testes) and an intact pituitary gland are required for the development of a healthy erectile system. As can be understood from the mechanisms of a normal erection, impotence may develop due to hormonal deficiency, disorders of the neural system, lack of adequate penile blood supply, or psychological problems. Restriction of blood flow can arise from impaired endothelial function due to the usual causes associated with coronary artery disease, but can also be caused by prolonged exposure to bright light.
There are several possible causes of ED, which include the following: drugs, neurogenic disorders (generalized anxiety disorder, personality disorders or traits), psychological problems, negative feelings, aging (making it four times higher in men in their 60s than in men in their 40s), kidney failure, diseases such as diabetes and multiple sclerosis (MS), and lifestyle.
Iatrogenic (Medical) Causes
Surgical intervention for a number of different conditions may remove anatomical structures necessary for erection, damage nerves, or impair blood supply. Complete removal of the prostate gland or external beam radiotherapy of the gland are common causes of impotence; both are treatments for prostate cancer. A study in 2002 found that ED can also be associated with bicycling. The number of hours on a bike and/or the pressure on the penis from the saddle of an upright bicycle is directly related to erectile dysfunction A recent study suggests an epidemiological association between chronic periodontitis (periodontal inflammation) and erectile dysfunction, similar to the association between periodontitis and coronary heart diseases, as well as cerebrovascular diseases. In all the three conditions (erectile dysfunction, coronary heart disease, and cerebrovascular diseases), despite the epidemiological association with periodontitis, no causative connection has yet been proven.
Treatments
Besides treating the major underlying causes such as potassium deficiency or arsenic contamination in drinking water, the primary treatment for erectile dysfunction consists of a trial of PDE5 inhibitor drugs (the first of which is sildenafil or Viagra). In some cases, treatment can involve prostaglandin tablets in the urethra, injections into the penis, a penile prosthesis, a penis pump, or vascular reconstructive surgery. Additional treatments for ED are varied and include a purpose-designed external vacuum pump used to attain erection, with a separate compression ring fitted to the penis to maintain it. These pumps should be distinguished from other penis pumps (supplied without compression rings) which, rather than being used for temporary treatment of impotence, are claimed to increase penis length if used frequently, or vibrate as an aid to masturbation. More drastically, inflatable or rigid penile implants may be fitted surgically. Medications carry risk of priapism.
The cyclic nucleotide phosphodiesterases constitutes a group of enzymes that catalyze the hydrolysis of the cyclic nucleotides cyclic AMP and cyclic GMP. They exist in different molecular forms and are unevenly distributed throughout the body. One of the forms of phosphodiesterase is termed PDE5. The prescription PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) are prescription drugs which are taken orally. They work by blocking the action of PDE5, which causes cGMP to degrade.