The female reproductive hormonal system regulates functions through interactions of hormones from the hypothalamus, anterior pituitary, and ovaries, with key hormones including gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH). The menstrual cycle, averaging 28 days, consists of the follicular phase, ovulation, luteal phase, and menstruation, during which hormones like estrogen and progesterone play critical roles in follicle development and endometrial preparation for potential implantation. If fertilization does not occur, hormonal levels drop, leading to menstruation, and the cycle restarts as FSH levels increase due to the lack of negative feedback.

2. Female hormonal system
Reproductive function in the female is regulated by interactions of
hormones from the hypothalamus, anterior pituitary, and ovaries. •
Gonadotropin-releasing hormone (GnRH) is the releasing factor from
the hypothalamus that stimulates secretion of follicle-stimulating
hormone (FSH) and luteinizing hormone (LH) from the anterior
pituitary. The release of GnRH is inhibited by estrogen and
progesterone. • LH is secreted from basophilic cells of the anterior
pituitary gland and stimulates development of the corpus luteum in
the ovaries. • FSH is secreted from the basophilic cells of the anterior
pituitary gland in response to GnRH and stimulates development of the
follicles in the ovaries. • Estrogen and progesterone are the steroid
hormones secreted by the follicle and corpus luteum of the ovary. The
28-day period of the female sexual cycle is determined by the time
required for the development of the follicles and corpus luteum after
menstruation and the feedback effect on the hypothalamus of the
hormones they secrete.

3. The menstrual cycle encompasses the ovarian
and uterine cycles.
• The ovarian cycle describes changes that occur in the follicles of the
ovary.
• The ovarian cycle controls the production and release of eggs and the
cyclic release of estrogen and progesterone.
• Uterine cycle describes changes in the endometrial lining of the uterus.
• The uterine cycle prepare and maintain the lining of the uterus.

6. Monthly ovarian cycle
• One mature ovum is released from the ovary during each monthly cycle,
and the endometrium of the uterus is prepared for implantation of the
fertilized ovum at the appropriate time. To achieve these results, all of
the hormones of the female reproductive system must interact.
• Menstrual cycle
• A normal menstrual cycle lasts 24-38 days( 28 days on average).
• Menses lasts an average of 3-7 days,with an average blood loss of 35-50ml.

7. Key Events in the Menstrual Cycle
• There are four key events that comprise a typical
menstrual cycle: follicular phase, ovulation, luteal
phase and menstruation
• Follicular phase can fluctuate in length
• Luteal phase is a fixed 14days,after which
menstruation occurs.
• Estrogen stimulates endometrial proliferation.
• Progesterone maintains endometrium to support
implantation.
• Low progesterone levels - decresed fertility.

8. Follicular phase and ovulation
• Follicle stimulating hormone (FSH) is secreted from the anterior
pituitary and stimulates growth of ovarian follicules.
• The dominant follicule produces estrogen, which inhibits FSH
secretion (negative feedback) to prevent other follicules growing.
• Estrogen acts on the uterus to stimulate the thickening of the
endometrial layer.
• Midway through the cycle (~ day 12), estrogen stimulates the anterior
pituitary to secrete hormones (positive feedback).
• This positive feedback results in a large surge of luteinizing hormone
(LH) and a lesser surge of FSH.
• LH causes the dominant follicule to rupture and release an egg – this
is called ovulation.
• Ruptured follicular cells differentiate into the corpus luteum.

9. Luteal phase and menstruation
• Change from estrogen to progesterone predominance: corpus luteum
produces progesterone and some estradiol,allowing to act on the uterus to
thicken the endometrial lining (in preparation for pregnancy).
• If fertilisation occurs, the developing embryo will implant in the
endometrium and release hormones to sustain the corpus luteum.
• If fertilisation doesn’t occur, the corpus luteum eventually degenerates
(forming a corpus albicans after ~ 2 weeks)
• When the corpus luteum degenerates, estrogen and progesteron
levels drop and the endometrium can no longer be maintained
• The endometrial layer is sloughed away and eliminated from the body
as menstrual blood (i.e. a woman’s period)
• As estrogen and progesterone levels are too low, there is no longer negative
feedback to FSH, which then increases restarts cycle again.

10. • Hormonal feedback loop
• The hypothalamus releases gonadotropin-releasing hormone (GnRH)
→ stimulates anterior pituitary gland to release follicle-
stimulating hormone (FSH),luteiizing hormone(LH).
• FSH recruits a group of maturing follicles in the ovary → growing
follicles produce estradiol and inhibin A at increasing levels
→ negative feedback to the pituitary gland → inhibits the release
of FSH.
• One follicle becomes the dominant follicle and estradiol levels peak at
the day before the luteinizing hormone (LH) surge → high levels
of estradiol induce positive feedback to the pituitary
gland → LH levels increase.
• LH surge induces ovulation → the mature oocyte is released from
the dominant follicle and the corpus
luteum produces progesterone → increase in progesterone inhibits LH
surge.
• Falling LH levels cause resolution of the corpus luteum → fall
in progesterone and estradiol levels.
• The hormonal feedback loop is also influenced by
other hormones (e.g., prolactin).

13. Summary of Ovarian cycle
• About every 28 days, gonadotropic hormones from the anterior
pituitary gland cause about 8 to 12 new follicles to begin to grow in
the ovaries. One of these follicles finally becomes “mature” and
ovulates on the 14th day of the cycle. During growth of the follicles,
mainly estrogen is secreted. After ovulation, the secretory cells of the
ovulating follicle develop into a corpus luteum that secretes large
quantities of both major female hormones, progesterone and
estrogen. After another 2 weeks, the corpus luteum degenerates,
whereupon the ovarian hormones estrogen and progesterone
decrease greatly, and menstruation begins. A new ovarian cycle then
follows.

14. Premenstrual syndrome(PMS)
• The onset of severe discomfort or functional impairment prior to
menstruation.
Diagnostic criteria:
• Present in the 5 days prior to the beginning of menstruation for at
least 3 consecutive cycles.
• End with 4 days after the beginning of menstruation.
• Interfere with normal daily life activities.
Epidemiology: UP to 12% of female individuals.