RESUMO
OBJECTIVES: The microdose of gonadotrophin-releasing hormone agonist (GnRHa) has been suggested as a beneficial method of ovulation induction for poor responders. However, the effect of microdose of GnRHa itself has not been evaluated yet. We performed a prospective sutdy to assess the effect of microdose of GnRHa (5 microgram of triptorelin acetate) on the luteinizing hormone (LH) and follicle stimulating hormone (FSH). Secondary objective of this study is to assess how long the down-regulation of gonadotrophin secretion by microdose GnRHa persists. METHODS: Five microgram of triptorelin was injected daily into five normally menstruating women for 7 days starting from cycle day 3. The blood sample was drawn for 12h with 4h interval, then for 6days with 4 h interval and once a day for 14days, In next cycle, same amount of triptorelin was injected into the same subjects daily for 3 days. The blood sample was drawn twice a day for 20days. Serum FSH, LH and extradiol level was measured. RESULTS: The serum LH and FSH level increased rapidly after injection of first GnRHa. The FSH level reached peak (27.53+/-6.34 IU/l) in 5h while LH level reached peak (34.35+/-7.18 IU/l) in 4h. The flare of gonadotrophins persisted even after second and third day injection of GnRHa, although the peak levels were not as high as first injection. The down regulation of gonadotrophin was established in 4-5 days. The estradiol level increased for 4-5 days then decreased. When GnRHa was given for 7days, the estradiol level began to rise 7-8 days after last injection; when given for 3days, the estradiol level began to rise 3-6 days after last injection. CONCLUSION: Even with ultra-low dose of GnRHa, the down-regulation of gonadotrophin could be achieved. The flare-up of gonadotrophin would persist for 3days with this dose. The duration of down regulation was influenced by the duration of GnRHa administration.
