Libido Male - The Male Libido
The Male Libido
Before the causes of erectile dysfunction are discussed, the normal aging-related changes in erectile function should be reviewed. Some men seeking help need only reassurance that their symptoms are age-related physiologic changes in function.
In young men, the higher centers of the brain are easily stimulated by fantasizing or thinking about sex, which seems to cause an erection nearly at will. With aging, this ability decreases. Ability to reach arousal with suggestive photographs also becomes less effective, although arousal by viewing a suggestive video may remain longer. Increased interaction of the couple, especially with foreplay, is needed to achieve a satisfactory erection.
Another aging-related change is an increase in the refractory period-that is, the time from ejaculation to the next erection. This interval may range from 30 minutes in a young man to several days in an octogenarian, according to the work of Masters and Johnson.
Erections, once achieved through fantasy and foreplay, are more fragile as men age. Older men must maintain their focus; if they allow themselves to be distracted by thinking of work or other activities, detumescence may occur. The telephone ringing may be enough to cause detumescence. In addition, men may occasionally experience detumescence without ejaculation for no apparent reason.
Causes of Erectile Dysfunction
The two main categories of dysfunction are psychologic and organic. Often the category is " mixed, " inasmuch as both factors are important. Every man who has some problem with erectile function has an element of performance anxiety, and determining whether psychologic factors are the main problem or merely a minor accompaniment may be difficult.
Organic causes are vascular, neurologic, hormonal, medical, or drug-related, and some men have multiple etiologic factors. Most of these causes affect the intrapenile vasculogenic mechanisms, whether arterial or venous. Another common finding is a decrease in local nitric oxide, which is thought to be the main neurotransmitter in initiating the erectile process. Intracorporeal fibrosis may also be present, which would limit the expandability of the corpora cavernosa, prevent the venules from compressing against the tunica albuginea, and thereby allow venous leakage from the penis.
Vascular Causes.- Among the vascular factors that can affect erectile function is a decreased blood flow to the penis. Decreased intrapenile circulation occurs if the corpora cavernosa cannot expand and fill with blood. Although atherosclerotic plaques, or damage by trauma or irradiation, decrease blood flow to the penis, vascular causes of erectile dysfunction are more often due to a failure of neural, muscular, or chemical factors. The vascular problem of venous origin, venous leakage, occurs when incomplete filling of the corpora, or intracavernosal fibrosis, causes failure of the veins to be pressed shut against the tunica albuginea.
Neurologic Causes.- A cerebrovascular accident (CVA or stroke ), demyelinating diseases, or even seizure disorders can cause erectile dysfunction. Tumors or trauma to the spinal cord could also be causative factors. peripheral nerves may be damaged by trauma or transurethral resection of the prostate . A common cause of impaired erectile and ejaculatory function is peripheral nerve damage due to diabetic autonomic neuropathy. This prevalence increases with time in both type 1 and type 2 diabetes , and the frequency of occurrence increases when the plasma glucose is poorly controlled.
Hormonal Abnormalities.- Hormonal causes are related to sexual dysfunction, especially erectile dysfunction. Most problems revolve around dysfunction of the hypothalamic-pituitary-gonadal axis and are associated with either excess prolactin or decreased testosterone levels. Other endocrine disorders that may cause libido or erectile difficulties include hypothyroidism, hyperthyroidism, adrenal insufficiency, or excessive levels of adrenal corticosteroids. In such cases, the effect is a generalized fatigue or weakness from the effects of the illness. Tumors of the hypothalamic-pituitary area may cause hypogonadism by mass effect, destruction of pituitary tissue, or oversecretion of prolactin, which may suppress gonadotropins and cause secondary hypogonadism. postreceptor action of increased prolactin levels may also cause erectile problems, even in the presence of a normal testosterone level.
prolactin overproduction due to medications, hypothyroidism with increased thyrotropin, chest wall injuries, or compression of the pituitary stalk can result in sexual problems. Rarely, if the patient has an excess of a variant large prolactin molecule, macroprolactin, the cause of the sexual difficulties will not be the prolactin because these molecules are biologically inert. Any major medical illness or surgical procedure can suppress the central axis and cause secondary hypogonadism. primary hypogonadism occurs in some men as they age. A common cause of primary testicular failure is autoimmune destruction of the testicles. Another factor is unilateral mumps orchitis during the early adult years, with later failure of the " good testis. "
Hypogonadism is defined as a free testosterone level that is below the lower limit of normal for young adult control subjects. previously, age-related decreases in free testosterone were once accepted as " normal. " Currently, they are not considered normal. Several clinical conditions were once accepted as normal age-related disorders but now are thought to be unhealthy-for example, hypertension, osteoporosis, and menopause. No agreement exists on the exact normal level of testosterone as men age or the serum testosterone level at which a man loses his sexual function. The definition of relative hypogonadism is also uncertain. Many men have perfectly normal sexual function even if their testosterone levels decline into the age-adjusted lower normal range. patients with low-normal to subnormal range testosterone levels warrant a clinical trial of testosterone. The threshold of response to testosterone, and thus the necessary dosage, varies-especially in the younger decades of life. If LH is increased and the testosterone level is low, the patient will have decompensated primary testicular failure. Testosterone replacement therapy is then essential.
Men with testicular failure may suffer from sexual dysfunction, as well as osteoporosis, anemia, muscle weakness, depression, and lassitude, which is the clinical spectrum of hypogonadism. The sexual dysfunction, especially decreased libido and decreased erectile capacity, often reverses with testosterone replacement therapy. The variability of response in some patients may be related to comorbid medical illnesses, vascular dysfunction at the penile level, or psychologic factors.
Medical Conditions.- Any medical condition that can cause general debility has the potential to decrease sexual desire and performance. pain, shortness of breath, angina, muscle weakness, or a CVA may be responsible for the dysfunction. The most common medical conditions associated with sexual difficulties are diabetes mellitus and hypertension , possibly because of the microvascular and neurovascular changes that are inherent in these conditions. In patients with diabetes, these factors may lead to a decrease in nerve stimulation and in nitric oxide generation. Some investigators have found hypogonadism to be commonly associated with diabetes mellitus. poorly controlled plasma glucose levels add a separate risk factor, as does the presence of diabetic neuropathy. Not only is hypertension a separate risk factor for sexual problems but hypertension and diabetes often coexist in the patient. Generalized atherosclerosis and peripheral vascular disease may impede blood flow to the penis, as may a damaged vessel from pelvic injury or radiation therapy to the groin. Tobacco (cigarette smoking) can cause vascular insufficiency as well as a decrease in intrapenile nitric oxide levels. Excessive consumption of alcohol or use of other recreational drugs may cause sexual dysfunction, either by a direct effect on the penile neurovascular system or by causing increased prolactin or decreased testosterone production (or both). peyronie's disease is a condition in which collagen tissue is converted to fibrous tissue, for unknown reasons; a palpable fibrous plaque created in the tunica albuginea causes bending of the penile shaft. The usual manifestation is a bend to one side during erection, which can occasionally be painful.
Drug-Related Causes.- Both prescription and over-the-counter medications have been shown to be the cause of erectile problems in as many as 25% of cases (Table 1). Although single medications can induce erectile dysfunction, the adverse medication effects are often additive. This situation is particularly frequent in older men who are taking multiple medications and in whom partial or complete erectile dysfunction often results. A psychologic component can make partial erectile dysfunction progress to complete erectile dysfunction. Some medications can affect libido, whereas others affect erectile function or ejaculation. Nonprescription medications, such as antihistamines or decongestants, may affect erectile function. Most psychotropic drugs can affect libido or erectile function, through either a direct action or an increased prolactin or a decreased testosterone level. Although antidepressants may cause dysfunction in susceptible patients, they may also be beneficial in improving libido in depressed men.
Antihypertensive medications may cause erectile dysfunction either by drug-specific effects or by decreasing the systolic pressure and thereby decreasing the intracavernosal penile pressure. This result is especially prevalent in patients with diabetes or hypertension who have an underlying microvascular disease. Ketoconazole, aminoglutethimide, and similar drugs actually decrease the production of testosterone. Most of the earlier antihypertensive agents-such as reserpine, guanethidine, and hydralazine-caused sexual dysfunction. Some b-adrenergic blocking agents may cause sexual problems, but dysfunction with angiotensin-converting enzyme inhibitors or calcium channel blockers is less common. Some drugs (spironolactone, cimetidine, flutamide, or cyproterone acetate) may block the peripheral androgen receptors. Cimetidine may assume a greater importance because it can now be purchased without a prescription. Drugs such as a-methyldopa, spironolactone, digoxin, metoclopramide, and many psychotropic agents may raise prolactin levels. Thiazide diuretics, finasteride, anticholinergics, and pain medications cause dysfunction in a certain percentage of patients.