The semen quality of
22
dogs (
4
to
7
years old) with benign prostatic hyperplasia (BPH) was examined at the hospital of our university, and
4
of the
22
BPH dogs were diagnosed as azoospermic. The mean peripheral plasma estradiol-17β (
E2
) level (17.
3
pg/m
l) of the 18 BPH dogs with spermatogenic function was higher than that of
5
normal male dogs and their mean T level (1.
7
ng/m
l) was lower. The mean
E2
level (27.
3
pg/m
l) of the
4
BPH dogs with azoospermia was significantly higher than the value in the BPH dogs with spermatogenic function (P<0.01), and the mean T level (1.1 ng/ml) was significantly lower (P<0.05). Five normal male dogs were given 10 intramuscular injections of estradiol benzoate (
E2B
)
5
μg/kg, at
3
-day intervals to investigate the relationship between high plasma
E2
levels and the cause of the BPH and azoospermia. Their testes and prostates were measured and biopsied both before and 30 days after the start of
E2B
injections. At 30 days after the start of the
E2B
injections, the mean peripheral plasma T levels had decreased by half, and the mean testicular volume had decreased to
88
% of original volume. The numbers of spermatocytes, spermatids, and spermatozoa in the seminiferous tubules of all of the dogs were significantly lower (P<0.05, 0.01). In addition, the mean prostatic volume increased to 130%, the mean height of the glandular epithelium decreased, and the glandular lumen became increased in diameter. These findings indicate that both BPH and serious spermatogenic dysfunction may be simultaneously induced by protracted high plasma
E2
levels in dogs.
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