Studies on GnRH agonist suppression of estrogen production in patients with endometriosis

The chronic administration of GnRH agonists to women results in the reversible suppression of estrogen production by the ovary. In the present study, the mechanism of the GnRH agonist suppression of estrogen production was investigated in patients with endometriosis. During the treatment with intranasal buserelin spray, the concentration of serum estradiol-17 beta (E2) was suppressed to near-castrate levels. Despite this marked suppression of serum E2, immunoreactive LH and FSH levels in serum were not changed. On the other hand, serum bioactive LH was markedly reduced. It was also observed during the treatment that the pituitary LH pulse disappeared and pituitary response to exogenous GnRH was significantly suppressed. In contrast, ovarian response to human menopausal gonadotropin (hMG) was not altered during the treatment. These findings suggest that the GnRH agonist suppression of estrogen production in the patients with endometriosis is through both suppression of the secretion of biologically active LH and the reduction of the LH pulse, but not through a direct inhibitory effect on ovarian estrogen biosynthesis.