Initial analysis of variability among basal hormone biomarkers of ovarian reserve

The most commonly used biomarker tests of ovarian reserve are basal hormone measurements during the early follicular phase, including mainly FSH but also oestradiol, FSH:LH ratio, and inhibin B. This study was designed to assess prospectively the intra- and inter-cycle variability of serum values of those hormone biomarkers in the early follicular phase of consecutive cycles in a group of women candidates for assisted reproduction. Fifty eumenorrhoeic women underwent blood sampling for hormone measurement on cycle day 3 for three consecutive cycles, and during the first study cycle, daily samples were obtained on cycle days 2, 3, 4 and 5. No significant difference was detected among FSH concentrations and FSH:LH ratios during cycle days 2-5; in contrast, oestradiol and inhibin B were not constant through the early follicular phase. No difference in FSH or inhibin B serum concentrations and FSH:LH ratio on cycle day 3 during three consecutive cycles was noted; however, significant inter-cycle variability for oestradiol serum concentration on cycle day 3 was detected. FSH and inhibin serum concentrations, and FSH:LH ratio varied significantly less than oestradiol on cycle day 3, but inter-cycle variability was similar for the first three hormonal biomarkers of ovarian reserve. There was significantly less intra-cycle variability of FSH serum concentration and FSH:LH ratio than oestradiol and inhibin B serum concentrations. Basal FSH serum concentrations (or FSH:LH ratio) during the early follicular phase showed neither significant inter-cycle nor intra-cycle variability when measured during 3 consecutive months in an assisted reproduction patient population, thus offering greater flexibility of pretreatment sampling.