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Many men when confronted with a
diagnosis of prostate cancer worry about their sexuality
almost as much as they do about their health. Prostate
cancer treatments can cause impotence,
however, the continual refinement in both techniques
and technologies for prostate cancer treatment and impotence
treatment are helping to reduce the occurrence of impotence.
There is sex after prostate cancer and there are many
tools to help patients engage in sex after prostate
cancer. Read on to find out about the physiological
and chemical reactions that produce erection. By learning
about what causes an erection, you will better be able
to select the proper method for coping with impotence.
Physiological Cause of Erection
Most people know that erections are caused by the flow
of blood into the three chambers of the penis. The corpora
cavernosa are two columns of spongy tissue that
make up 90 percent of the erectile tissue of the penis.
The corpus
spongiosum surround the urethra and holds only about
10 percent of the blood present in the penis during
erection.
During arousal, the smooth muscles
lining the veins of the arteries begin to relax. This
relaxation causes blood to flow in. The veins of the
penis begin to constrict; thus, blood can get in much
more easily then it can out. The penis can hold 10 times
the amount of blood when it is erect as opposed to when
it is not erect. After orgasm, the veins and arteries
return to normal and the blood flow returns to normal.
Prostate cancer treatments can affect the flow of blood
into the penis. Prostatectomy
has been known to divert the flow of blood into the
penis while radiation
treatment has been known to cause arteriosclerosis,
which is the hardening of the arteries.
Chemical Causes of Erection
An erection begins with arousal. The brain detects the
body becoming sexually aroused and transmits a message
along the NANC
neuron to tell the body to begin creating an erection.
NANC stands of nonadrenergic, noncholinergic and uses
nitric oxide to transmit the message. Once the nitric
oxide reaches the neurovascular
nerve bundles that hug the prostate gland, an enzyme
called guanosine
cyclase is released. An enzyme is like a biological
catalyst; it is a specially folded protein that fits
only into one substrate, like a key fits into only one
lock. A substrate is the compound that the enzyme will
change.
The substrate for guanylate cyclase
is called GTP or guanosine triphosphate. The guanosine
cyclase changes the GTP into cGMP.
cGMP causes the smooth muscles lining the arterial walls
of the penis to relax. cGMP, however, is broken down
by a second enzyme called phosphodiesterase
type 5 or PDE 5. PDE 5 turns cGMP back into guanosine
triphosphate or GTP to cause the arterial walls to not
relax and decreasing the blood flow into the penis.
The chemical cycle is started by the introduction of nitric oxide. The cycle begins with enzyme guanosine cyclase changing GTP into cGMP. The enzyme finishes when enzyme PDE 5 turns cGMP back into GTP.
Causes of Impotence
Both blood and nerves are necessary in producing
erection. Any prostate cancer treatment that upsets
the pathways to the penis can result in impotence. Radiation
therapy can impede the flow of blood to the penis by
arteriosclerosis. Prostatectomy can result in a diversion
of the blood flow. Both of these forms of impotence
may be helped by the use of a PDE 5 inhibitor which
prevents normal PDE 5 from breaking down cGMP. Examples
of oral PDE 5 inhibitors are sildenafil,
varendafil,
and tadalafil
which are trademarked respectively as Viagra, Levitra,
and Cialis.
PDE 5 inhibitors will not be helpful
for men who experience impotence due to a prostate cancer
treatment that has damaged the neurovascular bundles
that are attached to the NANC. Without the presence
of nitrous oxide, the chemical cycle never begins. Cryotherapy
and radical prostatectomy without nerve-sparing destroys
or removes these nerve bundles. Men for whom PDE 5 inhibitors
are ineffective or men who cannot take PDE 5 inhibitors
may want to consider other types of treatments for impotence
such as penile implants or the vacuum erection device.
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