By integrating morphometrical and endocrinological data, as well as biologi
cal effects of various peptides synthesized by the primate follicle, the cu
rrent review proposes a morphofunctional view of the early follicle growth
within the human ovary. From the time they enter the preantral stage (0.15
mm), during the early luteal phase, follicles need about 70 days to reach a
size of 2 mm. These follicles are impervious to cyclic FSH and LH changes
in terms of granulosa cell (GC) proliferation, and their steroidogenic acti
vity is very low. From the time they enter the selectable stage (2-5 mm in
diameter) during the late luteal phase, follicles become sensitive to cycli
c changes of FSH in terms of quality and GC proliferation, but not in terms
of GC aromatase activity. Thus, as the follicle develops, its responsivene
ss to gonadotropins progressively increases. In vitro studies suggest that
this progressive acquisition of follicular cell responsiveness to gonadotro
pins might be under the control of peptides acting in an autocrine/paracrin
e fashion within the follicle. The numbers of growing follicles decrease wi
th ageing, especially in women over the age of 40. During the follicular ph
ase of the menstrual cycle, selectable follicles exhibit a mitotic activity
of their GC higher in women older than 40 years than in younger women. (C)
1998 Elsevier Science Ireland Ltd. All rights reserved.