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ANDROGENS
AND ERECTILE DYSFUNCTION
Garolla,A.
University
of Padova, Department of histology, microbiology,
and medical biotechnologies, Centre for Male Gamete
Cryopreservation, Via Giustiniani 2, 35128 Padova,
Italy
It is
generally accepted that erectile response in mammals
is regulated by androgens both centrally and peripherally.
Androgens seem to exert regulatory action within the
central nervous system and in fact, castration decreases
erection after administration of apomorphine and testosterone
treatment restores this response. However, androgen
receptors have been identified also in cavernous tissue
and recently it has been demonstrated that androgens
are important for cGMP formation through a positive
modulation of NO synthase and upregulate PDE5 expression
in the penis, confirming their key role in the equilibrium
of the most important mechanism regulating the vasodilatation
of corpora cavernosa. We evaluated 700 patients referred
to our Centre from January 1999 to December 2001 for
erectile dysfunction. The prevalence of hypotestosteronemia
(total testosterone less than 3.0 ng/ml - 10.5 nmol/l)
was 21% (147 out of 700), and in 41 out of 147 (27.9%)
testosterone levels were very low (less than 2.0 ng/ml
- 7.0 nmol/l). The pathogenesis of hypotestosteronemia
in our patients is reported in tables 1 and 2. A total
of 15 men with severe hypogonadism (testosterone less
than 2.0 ng/ml) were recruited. The control group
consisted of 20 patients with psychogenic erectile
dysfunction. All subjects underwent nocturnal penile
tumescence (NPT) and rigidity monitoring during two
consecutive nights, evaluation of cavernous artery
flow using penile colour duplex ultrasound (P-CDU),
and real-time visually stimulated erections evaluation
at baseline and after administration of 50 mg sildenafil
or 3 mg apomorphine. NTP, P-CDU and visually stimulated
erection were evaluated after 6 months of therapy
with a 5 mg daily testosterone patch. NPT analysis
in subjects with severe hypogonadism showed a significant
decrease in sleep related erections. P-CDU showed
a partial erectile response with an alteration of
the of the parameters analyzed, and the visually stimulated
erection test was pathological. Administration of
3 mg apomorphine and 50 mg sildenafil has no influence
on erectile function. Testosterone treatment for 6
months induced normalization of NPT and P-CDU parameters,
and visually stimulated erection effects with the
restoration of a normal response to pharmacological
stimulation with apomorphine or sildenafil. In conclusion,
severe hypogonadism in men usually results in lower
libido, potency and alteration of sleep-related erections.
Our results show that testosterone has a key role
in the central and peripheral modulation of erectile
function even if the accurate testosterone plasma
level threshold that may influence these processes
remains to be established.
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