Penile erection hormonal system

ED can result from an abnormality in one of the four systems necessary for a normal penile erection or from a combination of abnormalities. Vascular, nervous, or hormonal etiologies of ED are referred to as organic ED. Abnormality of the fourth system (i.e., patient s psychological receptivity to sexual stimuli) is referred to as psychogenic ED. 

The physiology of penile erection involves an interplay of anatomical, hemodynamic, neurophysiological, and sex hormone interaction. Penile erection is the result of a complex interaction between the central nervous system and other local factors. This physical event also can be influenced by psychological factors. 

The incidence of erectile dysfunction is low in men less than 40 years of age. It increases as men age, likely as a result of concurrent medical conditions that impair the vascular, neurologic, psychogenic, and hormonal systems necessary for a normal penile erection. 

A normal penile erection requires the full functioning of several physiologic systems vascular, nervous, and hormonal. The patient must also be psychologically receptive to sexual stimuli. 

Erectile dysfunction can result from any single abnormality or combination of abnormalities of the four systems necessary for a normal penile erection. Vascular, neurologic, or hormonal etiologies of erectile dysfunction are collectively referred to as organic erectile dysfunction. About 80% of patients with erectile dysfunction have the organic type. Patients who fail to respond to psychogenic stimuli have psychogenic erectile dysfunction. 

These often involve regulation of transcription. As mentioned in Chapter 18, Section F,2, many of the effects of NO are a resulf of activation of soluble gua-nylate cyclase (p. 561). In the endothelium other hormones, such as the endothelins (p. 1750), atrial natriuretic factor, and bradykinin (Box 22-D), cooperate in the regulation of NO synthase. Neuronal NO synthase fimctions in the brain in olfaction and in formation of memory. In the peripheral system it mediates penile erection and plays a variety of roles in the enteric nervous system. Neuronal NO synthase is often localized to synaptic regions by binding to tissue-specific proteins. NO may also regulafe cellular respiration by inhibition of cytochrome c oxidase. ... 

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