serum fsh levels in women with polycystic ovary syndrome during ovulation induction using downregulation and urofollitropin objective to evaluate retrospectively the use of serum fsh levels and to correlate them with follicular growth in a clinical ovulation induction programmethods twenty women with infertility due to anovulation associated with polycystic ovary syndrome pcos were studied the patients were downregulated with a long gnrh agonist protocol and stimulated with purified urofollitropin using a lowdose stepup regimen repeated serum samples were drawn and transvaginal ultrasound scans wereperformed during the exogenous fsh therapy serum fsh levels resulting in continuous follicular growth were analyzed as well as the rates of ovulation pregnancy cancellation and conversion to in vitro fertilization jvfresults thirtytwo out of fifty treatment cycles led to ovulation resulting in five term pregnancies eight cycles were converted to ivfembryo transfer due to multiple follicular growth they resulted in two pregnancies ten cycles were cancelled because of impaired follicular growth the serum fsh levels median 6 iui resulting in continuous growth of the follicles were relatively stable within patients variation 15 but varied considerably between patients 45 the relationship between fsh dose and serum level was different for lean and obese pcos patients after subcutaneously injected urofollitropinconclusions there seems to be a difference in resorptionmetabolism between lean and obese pcos patients with regard to sc injected fsh the intrapatient coefficient of variation cv of the serum fsh response level was quite low as was the cv of the fsh dose at the response level this allowed a more rapid dose adjustment in subsequent cycles analysis of serum fsh during induction of ovulation with gonadotropins seems to be of limited value in clinical programs