Effects of Continuous LHRH Infusion on Plasma Levels of LH and FSH in Males, Before and After Oestrogen or Anti-Oestrogen Treatment

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 - Ethinyloestradiol - Continuous LHRH Infusion - LH - FSH