Immediately prior to ovulation, copious amounts of GnRH cause a surging
release of LH and FSH from the anterior pituitary. The surge in LH is responsible for
final maturation and ovulation of the oocyte (Bearden et a!., 2004), whereas FSH
stimulates growth of a new population of follicles. Following expulsion of the oocyte,
cells at the ovulation site transform into luteal cells, and thus, begin the luteal phase. The
luteal phase is denoted by formation of the corpus luteum and increasing concentrations
of progesterone. These events take place within the stages of metestrus and diestrus.
Follicular populations occur in a wave-like fashion with each wave consisting of follicle
recruitment, selection, and dominance (see Follicular Dynamics). Progesterone
production regulates release of LH through negative feedback on the hypothalamus.
Therefore in the presence of progesterone, frequency of GnRH release is reduced,
subsequently causing a reduction in LH and FSH release from the pituitary. However,
luteal cells require LH for progesterone production and follicle populations rely on
gonadotropins for proper development. Follicular growth continues under basal LH and
FSH release from the pituitary: however, a follicle cannot achieve preovulatory status in
the presence of progesterone. Additionally, estrogen production from the follicle is low
due to the inhibitory effects of progesterone (Senger, 1997).
The corpus luteum remains on the ovary for a period of 17 to 19 days following
Immediately prior to ovulation, copious amounts of GnRH cause a surgingrelease of LH and FSH from the anterior pituitary. The surge in LH is responsible forfinal maturation and ovulation of the oocyte (Bearden et a!., 2004), whereas FSHstimulates growth of a new population of follicles. Following expulsion of the oocyte,cells at the ovulation site transform into luteal cells, and thus, begin the luteal phase. Theluteal phase is denoted by formation of the corpus luteum and increasing concentrationsof progesterone. These events take place within the stages of metestrus and diestrus.Follicular populations occur in a wave-like fashion with each wave consisting of folliclerecruitment, selection, and dominance (see Follicular Dynamics). Progesteroneproduction regulates release of LH through negative feedback on the hypothalamus.Therefore in the presence of progesterone, frequency of GnRH release is reduced,subsequently causing a reduction in LH and FSH release from the pituitary. However,luteal cells require LH for progesterone production and follicle populations rely ongonadotropins for proper development. Follicular growth continues under basal LH andFSH release from the pituitary: however, a follicle cannot achieve preovulatory status inthe presence of progesterone. Additionally, estrogen production from the follicle is lowdue to the inhibitory effects of progesterone (Senger, 1997).The corpus luteum remains on the ovary for a period of 17 to 19 days following
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