Prospective analysis of the relationships between the ovarian follicle cohort and basal FSH concentration, the inhibin response to exogenous FSH and ovarian follicle number at different stages of the normal menstrual cycle and after pituitary down-regulation.
BACKGROUND
Analyses of the follicular reserve and activity of the ovary are central to our understanding of the regulation of follicular development. We have carried out a prospective analysis of endocrine and biophysical assessments under three differing basal conditions: the early follicular and mid-luteal phases, and following GnRH analogue down-regulation.


METHODS
Hormonal analyses were carried out before and after a single dose of FSH on spontaneously ovulating women (n = 58). Ovarian volume and antral follicle count (AFC) were also determined.


RESULTS
Inhibin B and estradiol concentrations were increased by FSH under all three conditions, and inhibin A in the follicular phase and after down-regulation. Basal hormone concentrations, except inhibin A and B after down-regulation, did not generally correlate with AFC. A close relationship between inhibin B and AFC was evident at all stages after FSH administration (r = 0.70-0.77). AFC and inhibin B after FSH stimulation were well correlated with the number of oocytes recovered after superovulation. Multivariate analysis demonstrated that inhibin B after FSH administration in the down-regulated state showed the closest correlation with oocyte number. In the more clinically useful early follicular and luteal phases, basal FSH was the most significant contributor to the number of oocytes, with a significant contribution from luteal phase AFC.


CONCLUSIONS
These data extend our understanding of the relationships between follicular number, follicular functional activity, and the recruitable follicular population. Down-regulation and subsequent FSH stimulation was required to clearly demonstrate the close relationship between inhibin B and the ovarian reserve. Without such complex manipulation, early follicular phase FSH (supplemented by AFC in the relatively hypogonadotrophic luteal phase) remains of greater value in predicting the ovarian reserve than the currently known direct products of the ovary.
Yong
Peter Y K
PY
Royal Infirmary of Edinburgh, University of Edinburgh, 49 Little France Crescent, Edinburgh EH16 4SB, UK.
Baird
David T
DT
Thong
K Joo
KJ
McNeilly
Alan S
AS
Anderson
Richard A
RA
D000328:Adult; D000375:Aging / Q000378:metabolism; D015536:Down-Regulation; D005260:Female; D005307:Fertilization in Vitro; D005640:Follicle Stimulating Hormone / Q000097:blood* / Q000494:pharmacology*; D005498:Follicular Phase; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives; D006728:Hormones / Q000097:blood; D006801:Humans; D007265:Inhibins / Q000097:blood*; D008183:Luteal Phase; D008597:Menstrual Cycle / Q000502:physiology*; D009865:Oocytes; D009994:Osmolar Concentration; D006080:Ovarian Follicle / Q000502:physiology*; D010062:Ovulation Induction; D010902:Pituitary Gland / Q000378:metabolism*; D011446:Prospective Studies; D011994:Recombinant Proteins / Q000494:pharmacology; D012016:Reference Values; D012044:Regression Analysis; D020858:Tissue and Organ Harvesting; D016896:Treatment Outcome
D006728:Hormones; D011994:Recombinant Proteins; D007987:Gonadotropin-Releasing Hormone; D007265:Inhibins; D005640:Follicle Stimulating Hormone