Endocrinological view of hormones in the ovarian cycle and the endometrial cycles.

1. Endocrinology
Hormonal Control Of Ovarian
and Endometrial Cycle
Presented By:
Girish Kumar K
III MSc
Biomedical Science

2. Ovarian Cycle
• The ovarian cycle is a series of events in the ovaries
that occur during and after the maturation of the
oocyte (egg or ovum).
• It is the development and release of oocytes in the
ovary and changes in the follicles.
• Ovarian cycle occurs within 28days and involves both
oogenesis, the process of formation and development
of oocyte, and preparation of the uterus to receive a
fertilized ovum.
• The cycle is consists of follicular phase and luteal
phase.

3. The Endometrial cycle
• It is the preparation of the lining of the uterus
(endometrium) for implantation by a fertilized
egg and shedding of the lining when
implantation has failed.
• The cycle consists of the menstrual
(menstruation), proliferative phase and
secretory phase.

4. • The two cycles occurs concurrently and regulated
by hormones released by the endocrine system.
• Changes in the ovary is regulated by the
hormones from anterior pituitary.
• Changes in endometrium is regulated by
hormones from ovary during the ovarian cycle.

5. Ovarian Cycle
Follicular Phase
• Occurs in the first half of the cycle
• Oocyte inside each follicle enlarges and thecal cells
in follicle secretes increased amount of oestrogen.
• Zona pellucida and antrum forms
• A rapid follicular growth continues during the
follicular phase.
• One follicle usually grows more rapidly & matures
about 14 days after onset of follicular development.

7. Hormonal Control Of Follicular
Phase

8. Ovulation
• Walls of the Graffian follicles
ruptures and thereby antral fluid
along with the oocytes flows to
ovarian surface.
• Fluids and the oocytes are
released and the oocytes enters
the uterine tube.
• Luteinizing hormone is triggered.
• Follicle(s) are released during
ovulation.

9. Luteal Phase
• It is the last 14 days of the ovarian cycle.
• Old follicular cells undergoes structural
transformation to form corpus luteum.
• Fully functional within four days after ovulation
and continues to increase in size for another 4-5
days.
• If released ovum is not fertilized and does not
implant, corpus luteum degenerates within about
14 days after formation.
• Hormonal control: LH causes development of
corpus luteum from empty Graafian follicle.

10. Hormonal Control of Ovulation

11. Endometrial Cycle
• Reflects from hormonal changes during
ovarian cycle.
• Averages for 28days.
• The cycle consists of three phases.
Menstrual phase
Proliferative phase (estrogen)
Secretory or progestational phase.
(progesterone)

12. Menstrual phase – In this phase there is a
decreased level of oestrogen and progesterone.
Uterine lining is shed from 5-7 days.
Proliferative phase – Increased level of
estrogen. Endometrium is renewed in the
preparation of possible pregnancy.
Secretory phase – Increased level of
progesterone. Endometrium is developed. The
phase coincides with the luteal phase.

13. Menstrual phase
• Characterized by discharge of blood and endometrial
debris from vagina .
• First day of menstruation is considered start of new cycle.
Coincides with end of ovarian luteal phase and onset of
follicular phase.
• Triggered by decreased oestrogen and progesterone:
hormones decrease when corpus luteum degenerates.
• Release of uterine prostaglandin.
• Causes vasoconstriction of endometrial vessels, disrupts
blood supply and causes death of endometrium.
• Stimulates mild rhythmic contractions of uterine
myometrium – Helps expel the menstrual flow

14. Proliferative phase
• Begins concurrent with last portion of ovarian
follicular phase.
• Uterus prepares for fertilized ovum.
• Endometrium starts to repair itself and
proliferate under influence of oestrogen from
newly-growing follicles.
• Oestrogen-dominant proliferative phase lasts
from end of menstruation to ovulation Peak
oestrogen levels trigger LH surge responsible for
ovulation

15. Secretory phase
• Endometrium prepares for implantation with increased blood
supply.
• Glands enlarges and secrete glycogen-rich fluids.
• Secretory phase conditions promoted by progesterone –
Uterus enters this phase after ovulation when new corpus
luteum is formed.
• Corpus luteum secretes large amounts of progesterone and
oestrogen.
• Progesterone converts endometrium to highly vascularized,
glycogen-filled tissue.
• Endometrial glands actively secrete glycogen.
• If fertilization and implantation do not occurs.
1. Corpus luteum degenerates.
2. New follicular phase and menstrual phase begin
again.

16. Timing Of Ovarian and
Endometrial cycles

17. Hormonal control of
Endometrial cycle
• FSH - Follicle stimulating hormone growth and
development of follicles.
• LH - Luteinising hormone causes ovulation
development of corpus luteum.
• Inhibin - Decreases FSH but not LH.

18. Oestrogen
• Stimulate oogenesis and follicle development.
• Promote proliferative-phase uterine conditions.
• Induce expression of uterine progesterone
receptors.
• Induce expression of granulosa cell LH receptors.
• Secondary sexual characteristics Breast growth
during pregnancy

19. Progesterone
• Promotes secretory-phase uterine conditions.
• Suppresses uterine contraction during
pregnancy.
• Promotes growth of glandular breast tissue
but suppresses milk production

20. • Oestrogen secreted first from the follicle, then
from the corpus luteum.
• Progesterone secreted from the corpus
luteum.
• LH and FSH secreted from the anterior
pituitary.
• Oestrogen and progesterone inhibit LH and
FSH secretion

24. 1. Which two hormones stimulate the
development of follicles in the follicular
phase of ovarian cycle?
2. What are the functions of the LH in luteal
phase?
3. Role of progesterone and oestrogen in the
endometrial cycle? Any two.

25. Answer:
1. FSH and Oestrogen.
2. LH causes development of corpus luteum from
empty Graafian follicle.
3. Progesterone - Promotes growth of glandular
breast tissue but suppresses milk production
-suppresses uterine contraction
during pregnancy.
Oestrogen - Stimulate oogenesis and follicle
development.
-Secondary sexual characteristics
Breast growth during pregnancy