[Estradiol benzoate test in the study of pituitary block induced by triptorelin]

The suppression of the positive oestradiol (E2) feed-back mechanism was studied in 21 patients during treatment with long acting GnRHa-triptorelin 3.75 mg (Ipsen-Biotech). A basal sample for FSH, LH and E2 evaluation was taken before a single administration of 2.5 mg of oestradiol benzoate (EB) i.m. at 24 and 48 hours later. The test was performed 1, 2, 3, 4, 5, 6 and 7 weeks after i.m. injection of GnRHa. The E2 concentration 24 hours after EB injection was > 400 pg/ml, able to induce, in physiological conditions, a positive feedback. In the other hand no FSH an LH rise was observed in all test after 1, 2, 3, 4, 5, 6 and 7 weeks from GnRHa administration. Our results show the absolute suppression of the positive feed-back mechanism during the treatment with a single dose of long acting tryptorelin 3.75 mg i.m., the same results were obtained until the 7th week after GnRHa administration.