Summary
In order to study the role of oestrogens on gonadotrophin release in the human male,
LHRH was administered as an infusion at a constant rate of 0.5 micrograms/minute for
4 hours to 7 normogonadotrophic oligozoospermic men, 6 eugonadal male-to-female transsexuals
and 9 eugonadal male volunteers.
In agreement with in vitro data a biphasic release pattern of both LH and FSH was observed in eugonadal trans-sexuals
as well as in normogonadotrophic oligoospermic men. In the latter the release of LH
was greater than in eugonadal transsexual males and volunteers, which points to a
different functioning of the hypothalamic-pituitary unit in normogonadotrophic oligozoospermic
men. On the other hand the FSH response to LHRH stimulation was normal in these men.
Three months' treatment with the oestrogen-receptor antagonist tamoxifen (TAM) (10
mg twice daily) in the normogonadotrophic oligozoospermic men stimulated basal LH,
FSH and testosterone (T) levels. The fact that gonadotrophin levels rose in spite
of increased T levels, suggests a role of endogenous oestrogens in the negative feedback
regulation of gonadotrophin release in these men.
Upon TAM treatment the first phase, the plateau and the second phase of LH release
were augmented, whereas only the plateau and the second phase of FSH release were
increased.
Six weeks' administration of the oestrogen ethinyl-oestradiol (EE) (10 micrograms
three times a day) in the eugonadal transsexual males suppressed basal T and oestradiol
(E2) levels without affecting basal gonadotrophin levels significantly. In EE-treated
males the first phase of LH release tended to be lower, whereas the plateau of LH
had decreased significantly. The second phase of LH was unaffected.
For FSH the plateau and the second phase of release tended to be lower, whereas the
first phase was unaffected.
Considering the effects of administration of oestrogen and anti-oestrogen on LHRH-induced
LH and FSH release it appears that particularly the first part (0-90 minutes) of LH
release is oestrogen-sensitive, whereas for FSH this is the second part (40-240 minutes).
Key-Words
Tamoxifen
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Ethinyloestradiol
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Continuous LHRH Infusion
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LH
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FSH
