Provided
by National Institute of Diabetes and Digestive and Kidney Diseases
Erectile
dysfunction, sometimes called "impotence," is the repeated inability
to get or keep an erection firm enough for sexual intercourse. The word "impotence"
may also be used to describe other problems that interfere with sexual intercourse
and reproduction, such as lack of sexual desire and problems with ejaculation
or orgasm. Using the term erectile dysfunction makes it clear that those other
problems are not involved.
Erectile
dysfunction, or ED, can be a total inability to achieve erection, an inconsistent
ability to do so, or a tendency to sustain only brief erections. These variations
make defining ED and estimating its incidence difficult. Estimates range from
15 million to 30 million, depending on the definition used. According to the National
Ambulatory Medical Care Survey (NAMCS), for every 1,000 men in the United States,
7.7 physician office visits were made for ED in 1985. By 1999, that rate had nearly
tripled to 22.3. The increase happened gradually, presumably as treatments such
as vacuum devices and injectable drugs became more widely available and discussing
erectile function became accepted. Perhaps the most publicized advance was the
introduction of the oral drug sildenafil citrate (Viagra) in March 1998. NAMCS
data on new drugs show an estimated 2.6 million mentions of Viagra at physician
office visits in 1999, and one-third of those mentions occurred during visits
for a diagnosis other than ED.
In
older men, ED usually has a physical cause, such as disease, injury, or side effects
of drugs. Any disorder that causes injury to the nerves or impairs blood flow
in the penis has the potential to cause ED. Incidence increases with age: About
5 percent of 40-year-old men and between 15 and 25 percent of 65-year-old men
experience ED. But it is not an inevitable part of aging.
ED
is treatable at any age, and awareness of this fact has been growing. More men
have been seeking help and returning to normal sexual activity because of improved,
successful treatments for ED. Urologists, who specialize in problems of the urinary
tract, have traditionally treated ED; however, urologists accounted for only 25
percent of Viagra mentions in 1999.
How
Does An Erection Occur?
Erection
begins with sensory or mental stimulation, or both. Impulses from the brain and
local nerves cause the muscles of the corpora cavernosa to relax, allowing blood
to flow in and fill the spaces. The blood creates pressure in the corpora cavernosa,
making the penis expand. The tunica albuginea helps trap the blood in the corpora
cavernosa, thereby sustaining erection. When muscles in the penis contract to
stop the inflow of blood and open outflow channels, erection is reversed.
dib
Figure
1. Arteries (top) and veins (bottom) penetrate the long, filled cavities running
the length of the penis--the corpora cavernosa and the corpous sponglosum. Erection
occurs when relaxed muscles allow the corpora cavernosa to fill with excess blood
fed by the arteries, while drainage of blood through the veins is blocked.
