Three basic mechanisms can lead to erectile dysfunction:

i)Inability to initiate: This could be endocrinologic ,neurogenic ,or psychogenic

ii)Inability to fill: That is arteriogenic

iii)Inability to store adequate blood volume in the lacuna : ie venoocclusive

Vasculogenic Causes:

This will be treated first as it  is the most frequent cause of erectile dysfunction. Here there is a disturbance in the blood flow to and from the penis.

The blood flow to the lacunar spaces in the penis can be decreased in atherosclerosis and traumatic arterial diseases.This results in increased time for full erection and decreased rigidity.

Insufficient relaxation of the trabecular smooth muscle can lead to excessive outflow through the veins even if there is adequate inflow through the arteries.

Endocrinologic Causes:

It is a well established fact that androgens increase libido.

The exact mechanism by which androgens increase libido is not well understood.

Normal testosterone levels are  important ,especially in older males for erectile function.

Erectile dysfunction secondary to hypogonadism can be improved by androgens

Another endocrine cause of impotence is increased level of prolactin .This suppresses gonadotropin-releasing hormone (GnRH), and it also leads to decreased testosterone levels. In these cases normal testosterone and libido can be restored with dopamine agonists, eg bromocriptene .

Diabetes and erectile dysfunction:

35 to 75% of diabetic men suffer from erectile dysfunction. This is mainly due to diabetic vasculopathy or neuropathy.

Diabetics have decreased levels of nitric oxide synthase in the endothelial and neural tissues. Nitric oxide is very important in erection.

Both diabetic microvascular and macrovascular complications can cause erectile dysfunction. Macrovascular complications of diabetes are age related while microvascular complications are related to the duration of diabetes and degree of glycemic control.

Neurogenic Causes:

Damage to the nerves to the penis can result in erectile dysfunction. This can be due to damages/disorders that affect the spinal cord or to the autonomic nerve fibers to the penis.

Spinal cord injury and pelvic surgery can cause erectile dysfunction. Pelvic surgery may disrupt the autonomic nerve supply.

In spinal cord injury, the severity of the erectile dysfunction depends on the level of injury and the completeness of the injury. Injuries to the upper part/incomplete injuries may not lead to erectile dysfunction or may cause mild degrees of erectile dysfunction. Patients with complete injuries or damage to the lower part of the spinal cord usually suffer from erectile dysfunction.

Approximately 75% of patients with spinal cord injury will have some form of erectile capability, but only 25% will have erection sufficient for penetration.

It most be noted that there are many other medical disorders that can affect the spinal cord and /or nerves and lead to erectile dysfunction. Some examples include multiple sclerosis and peripheral neuropathy (eg due to diabetes, alcohol etc).

Psychogenic Causes:

The common psychogenic causes of erectile dysfunction are anxiety, depression, conflicts in relationship, sexual abuse in childhood,loss of attraction, sexual inhibition, conflicts over sexual preference, fear of sexually transmitted diseases and fear of pregnancy.

Even patients with organic causes of erectile dysfunction develop a psychogenic component as a reaction to the erectile dysfunction.

References:

Pages 272 to 274,Chapter 43. Sexual dysfunction. Part II Cardinal Manifestations and Presentation of Diseases. Harrison’s Principles of Internal Medicine, 16th Edition by Kasper, Braunwald, Fauci, Hauser, Longo and Jameson. Volume I. Mc Graw Hill publication.

Erectile dysfunction is defined as the inability to reach erection or sustain it long enough for satisfactory coitus.

Another definition is ” Erectile dysfunction is defined as the consistent inability to maintain an erect  penis with sufficient rigidity to allow sexual intercourse.

Erectile dysfunction is not considered a normal part of aging process.

Types of erectile dysfunction/impotence:

Erectile dysfunction may be primary or secondary.

Secondary erectile dysfunction (erectile dysfunction due to other causes eg drugs) is the commonest type.

Primary erectile dysfunction- Never had erection before. This is very rare and due to physical causes such as neurological damage.

Incidence and prevalence:

Erectile dysfunction affects 10 million American men.

Approximately 25% of all men older than 65 years of age suffer from this disorder.

According to the MMAS (Massachusetts male aging study-community survey of men between the ages of 40 and 70), 52% of respondents reported some degree of erectile dysfunction. There was complete erectile dysfunction in 10% of respondents, moderate erectile dysfunction in 25% and minimal erectile dysfunction in 17%. The incidence of severe and moderate erectile dysfunction was increased between the ages of 40 and 70.

According to the NHSLS (National health and social life survey-USA) 10% of men responded that they were not able to maintain an erection. The incidence was highest among men in the 50 to 59 age group.

Common causes of secondary erectile dysfunction:

i) Alcohol abuse

ii) Diabetes

iii)Anxiety about sexual performance.

iv)Side effects of drugs-see below.

v)Arteriosclerosis.

vi) Other physical diseases such as pelvic autonomic neuropathy, hyperprolactinaemia and rectal surgery.

Drugs associated with erectile dysfunction- eg of secondary cause

Antihypertensives

Calcium channel blockers

Methyldopa

Clonidine

Reserpine

Beta blockers

Guanethidine

Diuretics

Spironolactone

Thiazides

Antidepressents

Selective serotonin reuptake inhibitors

Lithium

Tricyclic antidepressants

Monoamine oxidase inhibitors

Cardiac

Digoxin

Anti-hyperlipidemics

Gemfibrozil

Clofibrate

Tranquilizers

Butyrophenones

Phenothiazines

H-2 Antagonists

Ranitidine

Cimetidine

Cytotoxic agents

Cyclophosphamide

Methotrexate

Roferon-A

Recreational Drugs

Ethanol

Cocaine

Marijuana

Anticholinergics

Disopyramide

Anticonvulsants

Hormones

Progesterone

Estrogens

Corticosteroids

GnRH agonists

5-alpha reductase inhibitors

Cyproterone acetate.

Investigations and management of male erectile dysfunction will be covered in a subsequent post.

The detailed causes and pathophysiology of erectile dysfunction will also be covered in a subsequent post.

References:

Lack of libido and erectile dysfunction, page 1055,Chapter 18 .Endocrine Disease-Reproduction and Sex. Clinical Medicine by Kumar and Clark ,Sixth edition.Edited by Parveen Kumar and Michael Clark.

Pages 297 to 299,Male erectile dysfunction.Chapter 14,Problems of Sexuality and Gender. Psychiatry 2nd edition Oxford Core Texts by Michael Gelder, Richard Mayou and John Geddes.

Pages 272 to 274,Chapter 43. Sexual dysfunction. Part II Cardinal Manifestations and Presentation of Diseases. Harrison’s Principles of Internal Medicine, 16th Edition by Kasper, Braunwald, Fauci, Hauser, Longo and Jameson. Volume I. Mc Graw Hill publication.

Pages 950 to 952, Male Erectile Dysfunction and Sxual Dysfunction.Chapter 23 .2006 Current Medical Diagnosis and Treatment 45th edition. Edited by Lawrence M Tierney,Jr. Stephen J. McPhee and Maxine A. Papadakis.

There are important differences between the sexual response cycle in men and women. This difference is important when counseling individuals with sexual problems. The most important difference in the sexual response between men and women is the longer time taken by women to reach the arousal phase.

The sexual response cycle (Sex Drive) , consists of four phases:

1)Desire (Excitement)

2)Arousal (can be divided into excitement and plateau).

3) Orgasm

4) Resolution.

The sexual response staircase:

This is a similar concept to the sexual response cycle (above)

Here we try to give climbing up the stairs as an analogy to the human sexual response. This is very useful for education, diagnostic and therapeutic purposes.

Ground Level: Non-Sexual

Step 1: Here there is desire without any physical changes.

Step 2 :Arousal begins. In men the penis begins to get hard, but not firm enough for penetration. The woman begins to lubricate.

Step 3: Progress of arousal. Here the man gets a firm erection, that could achieve penetration. In women there is more lubrication and vaginal ballooning.

Step 4: Imminent orgasm

Step 5: Orgasm.

Sliding down the banisters: This is the process of resolution.

Physiological changes (Body Changes) in Women during Sexual Intercourse.

In women fluid is secreted onto the vaginal walls during sexual excitement. The secretion of fluids is probably mediated by the release of VIP (Vasoactive intestinal polypeptide ) from the vaginal nerves.

There is also release of mucus from the vestibular glands. The mucus helps in the lubrication during the sexual activity.

The upper two-thirds of the vagina stretches easily during sexual excitement.

The most sensitive part of the female genetalia is the clitoris and labia minora. Touching these parts can further add to the sexual excitement.

Tactile stimuli from the breast can also reinforce the sexual excitement.

Throughout orgasm there are rhythmic contractions of the vaginal wall which are automatically mediated. During orgasm there are also rhythmic contractions of the bulbocavernosus and ischiocavernosus muscles. This is due to the impulses travelling in the pudendal nerves.

It is thought that vaginal contractions may aid sperm transport, but it is not very important for fertilization to occur, since fertilization is not dependent on orgasm.

For more details see female sexual response (Below)

Physiological changes (Body Changes) in Men during Sexual Intercourse.

In men the sexual stimuli are reinforced by visual, auditory and olfactory stimuli.

For more details see male sexual response (Below)

The Male Sexual Response

Excitement:

Here there is erection of the penis.

The pulse rate and blood pressure are increased.

The testes is raised and the skin thickness of the scrotum increases.

Plateau:

In the plateau phase erection is maintained and the testes rises further.

There is further increase in the pulse rate and blood pressure.

The respiratory rate increases.

Orgasm:

During orgasm the urethra contracts repeatedly. There is also contraction of the prostate and seminal vesicles with emission of seminal fluid to the urethra.

There is further rise in the blood pressure, pulse rate and respiratory rate.

Resolution:

The erection gradually goes down (Gradual detumescence)

The scrotum thickness, blood pressure, pulse rate and respiratory rate return to normal.

The Female Sexual Response

Excitement:

During the excitement phase of the sexual response there is a slight elevation in the pulse rate and blood pressure.

Some women may have nipple erection.

The head of the clitoris swells, while the body of the uterus and cervix is raised.

There is expansion, lubrication and distension of the inner two-thirds of the vagina.

Plateau:

The areolar of the breasts get engorged and enlarged. There is also engorgement of the labia

There is withdrawal of the head of the clitoris and further elevation of the uterus.

The respiratory rate rises and there is further increase in the blood pressure and pulse rate.

There is swelling of the outer third of the vagina and further distension of the inner two-thirds.

Orgasm:

During orgasm there are contractions in the uterus and outer third of the vagina.

There is further rise in the blood pressure, pulse rate and respiratory rate.

Resolution:

The uterus returns to normal position while the os gapes open.

The changes in the breasts,vagina, clitoris,labia,uterus,pulse rate,blood pressure and respiratory rate all return to normal.

References:

Page 423, Chapter 23, Changes During Sexual Intercourse. The gonads, development and function of the reproductive system. Review of medical physiology. 20th edition by William F Ganong. Lange Publications.

Page 247 Specific sex therapy concepts and strategies. Sexual problems . Psychological aspects of gynecology.Chapter 20. Gynaecology by ten teachers, 17th edition by Stuart Campbell and Ash Monga.

Chapter 14,Problems of Sexuality and Gender. Psychiatry 2nd edition Oxford Core Texts by Michael Gelder, Richard Mayou and John Geddes.

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