研究開発・学会発表

【Background】 An aromatase inhibitor letrozole is frequently used to induce follicle growth in ovum pickup (OPU) cycles, but its effectiveness in poor responders is not clearly understood.

【Aim】 To evaluate the effectiveness of aromatase inhibitor in stimulating follicular growth in poor responders, we investigated the relationship between the basal levels of estradiol (E2) and FSH and follicular responsiveness in OPU cycles.

【Method】 Patients in cycles with low E2 (<5pg/ml) and/or high FSH (≧20mIU/ml) on the third day of withdrawal bleeding after the administration of EP (ethinyl estradiol + norgesterel) to whom letrozole was given orally in a dose of 2.5mg on CD3-7 were recruited as candidates of our investigation. Follicle growth was assessed by measuring the size of follicles and the levels of E2.

【Result】 In cases with low E2, the success rate of follicle growth was 91.3% when FSH levels were <10mIU/ml, but the rate decreased to 70.2%, 35.3%, 9.0% when FSH levels increased to 10-19.9mIU/ml, 20-29.9mIU/ml, ≧30mIU/ml respectively. On the other hand, success rate of follicle growth in cases with high FSH was also dependent on the levels of E2 as 29.6%, 58.3%, 79.2% and 95.1% when the levels of E2 were <5pg/ml, 5-9.9pg/ml, 10-19.9pg/ml and ≧20pg/ml respectively.

 【Conclusion】 It is possible to induce follicle growth with an aromatase inhibitor in many hypergonadotropic hypogonadal patients, if FSH levels can be suppressed enough with E2 levels kept over10pg/ml by EP administration.