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 during low dose step-up gonadotrophin therapy in patients with polycystic ovary syndrome (PCOS). To obtain stable levels of FSH, Metrodin was administered i.v. By making daily determinations, the FSH concentration was slowly increased in steps of approximately 1 IU/l. A total of 16 patients were treated for a maximum of three treatment cycles. Out of 38 treatment cycles, in 26 (68%) a single dominant follicle developed. The overall ovulation rate was 78%. FSH concentrations were evaluated with regard to intra- and interindividual variability of the FSH threshold and with regard to the relationship between FSH concentrations, FSH dose and treatment outcome. The high variability of the FSH threshold, ranging from 5.7 to 12 IU/l, appeared to be mainly a function of inter-individual variability. Higher FSH concentrations were associated with multifollicular growth as opposed to monofollicular growth, whereas the increases in concentration from a substimulating to a stimulating level were not. Multifollicular growth might thus be associated with a higher elevation of FSH concentration above the threshold. Different patterns of FSH concentration in the course of the growth phase of the dominant follicle in mono- compared to multifollicular cycles suggested a difference in the effect of endogenous FSH on the plasma concentration. Endogenous feedback on FSH release may therefore still play a role during treatment with exogenous FSH.