1. Physiology of the menstrual cycle
DR. AHMED ABDULWAHAB
Assistant Professor, Consultant
OBGYN Department

2. Objectives
List the names of different hormones involved in the production of menstrual cycle .
Know their origin and the nature of each hormone.
Describe how ovulatory menstrual cycle is produced and how does ovulation occurs .
Describe the morphological changes in the ovaries and endometrium in different phases of menstrual cycle .
Know the dominating hormones in each phase of menstrual cycle

3. Menstrual cycle represent a complex interaction between the hypothalamus, pituitary, ovaries and endometrium , these cyclical changes in gonadotrophins induce a functional as well as morphological changes in ovaries resulting in ovulation and corpus luteum formation and also at the endmetrium level.

4. THE HYPOTHALAMUS.
Is controlling the pituitary gland through releasing hormones which are peptide hormones .
they are very important in the synthesis and release of the trophic hormones of the pituitary gland except prolactin hormone which is under inhibitory effect , dopamine effect.

5. The trophic hormones are glycoprotiens ,
The gonadotrophins are follicle stimulating hormone FSH and lutenizing hormones LH ,
all contain alpha and beta subunits alpha subunit is similar in all hormones but beta subunit is specific to individual hormone.

6. Normal ovulatory cycle is divided into proliferative or follicular phase and secretory or luteal phase .
Follicular phase starts with the onset of the menses till pre ovulatory LH surge and ovulation , luteal phase then starts till next menses .

8. OVARIAN CYCLE.
ESTROGENS, mainly estradiol E2 ,is relatively low at the beginning of the follicular phase then increase rapidly reach a maximum one day before the LH surge .
Just before ovulation there is a marked fall, during the luteal phase E2 rises to a maximum 5-7 days after ovulation and return to base line shortly before menses.

9. PROGESTERONE.
Is secreted in small amount in the follicular phase but start to increase just before ovulation also reach a maximum 5-7 days after ovulation and return to baseline shortly before menstruation

10. FOLLICULAR DEVELOPMENT.
It starts since fetal development and known as the primordial follicles .
Under the effect of FSH the adult ovary containing the graffian follicles which is an oocyte covered with granulosa cell and theca cell start to grow ,
usually many follicles are recruited every cycle and only one usually continue differentiation and

11. Cont.
Maturation and ultimately ovulate .
The remaining follicles become atretic
Follicular maturation depends on FSH and LH receptors ,the FSH receptors are found in granulosa cell where LH receptors are found in theca cell .
Granulosa cell secretes E2 and when increase will cause a negative feedback

12. Cont.
Effect on the hypothalamus and pituitary gland and will stimulate proliferation of the endometrium .
The rest of the follicles will not find enough hormone to survive .
FSH will also enhance the induction of LH receptors on the granulosa cell .
E2 causes the LH surge

13. OVULATION.
When the follicle mean diameter reach mm LH surge will initiate sequence of structural and biochemical changes resulting in ovulation .
CORPUS LUTEUM .
After ovulation the granulosa cell of the ruptured follicle undergo lutenization these cell plus the surrounding theca cell

14. Cont.
Form the corpus luteum which produces copious amount of progesterone and little estrogen .
The normal life span of the corpus luteum is 10 days then it regress and replaced by an avascular scar called corpus albicans.
Next menses will come unless pregnancy occurs.