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Impotence may be caused by a variety of endocrine, vascular, neurologic, or psychiatric diseases. It may actually be the presenting symptom in some systemic diseases, or it can be a side effect caused by certain medications. Simply defined, impotence is the failure to achieve erection, ejaculation, or both.(1) Men may present with one or a combination of complaints: loss of libido, inability to initiate or maintain an erection, premature ejaculation, ejaculatory failure, or inability to achieve orgasm. The selection and success of therapy is dependent upon understanding the etiology, and thus it is necessary to evaluate all aspects of sexual function. It was previously thought that most erectile dysfunction was psychologically based. It is now thought that the majority of men with sexual dysfunction actually have a component of underlying organic disease.
A decrease or loss of desire (libido) may be due to androgen deficiency arising from either pituitary or testicular disease, psychological disturbance, or to some types of prescribed or habitually abused drugs.(1) If androgen deficiency is suspected, plasma testosterone and gonadotropin levels may be drawn. Hypogonadism may also result in the absence of emission secondary to decreased secretion of ejaculate by the seminal vesicles and prostate. The minimal level of testosterone necessary for normal erectile function is unknown.
Failure of erection may be caused by a number of conditions, grouped in general into endocrine, drug, local, neurologic, and vascular disorders.
Endocrine causes include primary or secondary testicular failure, and hyperprolactinemia. Lack of testosterone secondary to testicular failure is uncommon; however, it is an easily recognized and treatable disorder. A borderline decrease in testosterone will not cause sexual dysfunction. Hyperprolactinemia may cause impotence by suppressing the production of luteinizing hormone-releasing hormone. This causes a low or low normal level of testosterone and plasma gonadotropin that may be present in patients with pituitary tumors that have been unrecognized on physical examination.
Numerous drugs have been implicated in impotence, but those most frequently associated with erectile dysfunction are the antihypertensives, cimetidine, and monoamine oxidase inhibitors. The antihypertensives most often implicated are those with peripheral and central sympatholytic action or beta-adrenergic receptor blocking activity. Angiotensin converting enzyme (ACE) inhibitors and calcium channel blockers and peripheral vasodilators do not cause sexual dysfunction. Cimetidine and other histamine receptor antagonists have antiandrogenic properties. They have also been shown to increase prolactin levels. Other drugs with antiandrogenic action include spironolactone, ketoconazole, and finasteride. Finasteride, used commonly for the treatment of benign prostatic hyperplasia (BPH), produces impotence, decreased libido, or impaired ejaculation in 10-12 percent of men.
The antipsychotic effects on sexual function can be frightening or devastating to most schizophrenics and can adversely affect compliance. Erectile dysfunction and impotence, considered an anticholinergic effect, occurs in 25-60 percent of patients, most frequently with thioridazine.(2) Although impotence can also occur in a large number of untreated psychiatric patients, it is most certainly compounded by the use of antipsychotic drugs. Tricyclic antidepressants and monoamine oxidase inhibitors may also impair sexual function via anticholinergic and sympatholytic actions.
Many types of neurologic disorders cause impotence, including lesions in the anterior temporal lobe, spinal cord disorders, insufficiency of sensory input as in tabes dorsalis, or damage to parasympathetic nerves, for example, following surgical procedures such as radical prostatect
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