Use of a gonadotropin-releasing hormone agonist during ovarian stimulation leads to significant concentrations of peptide in follicular fluids.

The penetration of a gonadotropin-releasing hormone agonist (GnRH-a), Buserelin (Hoechst AG, Frankfurt, West Germany), into human follicular fluids (FF) was studied by means of a radioimmunoassay (RIA) and a bioassay. Acute nasal administration of a therapeutic dose of Buserelin (300 and 600 micrograms) before the ovum pickup for in vitro fertilization leads to significant concentrations of Buserelin in one-third of the FF. These concentrations ranged between 28 and 124 pg/ml, which represents 10% to 50% of the serum concentrations achieved in these patients. Follicular penetration of this agonist is time-dependent. Chronic administration during the follicular phase leads to low but significant concentrations of peptide 36 hours after the last inhalation. A very good correlation was observed between the RIA and the bioassay. This demonstrates the accuracy and the specificity of the RIA. In addition, it indicates that the Buserelin that reaches follicles is intact and is not the inactive product of degradation. Intranasal administration of Buserelin stopped 35 hours before ovum pickup appears to be an adequate way of minimizing the exposure of maturing oocytes to the GnRH-a.