FOLLICLE-STIMULATING-HORMONE (FSH) DYNAMICS OF LOW-DOSE STEP-UP OVULATION INDUCTION WITH FSH IN PATIENTS WITH POLYCYSTIC-OVARY-SYNDROME

Pharmacodynamics of follicle stimulating hormone (FSH) were studied du ring low dose step-up gonadotrophin therapy in patients with polycysti c ovary syndrome (PCOS). To obtain stable levels of FSH, Metrodin was administered i.v. By making daily determinations, the FSH concentratio n was slowly increased in steps of similar to 1 IU/l. A total of 16 pa tients were treated for a maximum of three treatment cycles. Out of 38 treatment cycles, in 26 (68%) a single dominant follicle developed. T he overall ovulation rate was 78%. FSH concentrations were evaluated w ith regard to intra- and interindividual variability of the FSH thresh old and with regard to the relationship between FSH concentrations, FS H dose and treatment outcome. The high variability of the FSH threshol d, ranging from 5.7 to 12 IU/l, appeared to be mainly a function of in ter-individual variability. Higher FSH concentrations were associated with multifollicular growth as opposed to monofollicular growth, where as the increases in concentration from a substimulating to a stimulati ng level were not. Multifollicular growth might thus be associated wit h a higher elevation of FSH concentration above the threshold. Differe nt patterns of FSH concentration in the course of the growth phase of the dominant follicle in mono- compared to multifollicular cycles sugg ested a difference in the effect of endogenous FSH on the plasma conce ntration. Endogenous feedback on FSH release may therefore still play a role during treatment with exogenous FSH.