Menstrual Cycle

The hormonal changes during puberty in females are called the menstrual cycle. The reproductive cycle in the female primates (e.g. monkeys, apes, and human beings) is called the menstrual cycle. In this cycle body of the female prepares itself for the possible pregnancy.
If the pregnancy does not occur then the body aborts all the preparations and restart the preparation for pregnancy again in a cyclic manner. The onset(start) of the 
  1. Menstrual cycle – Menarch (occurs at puberty 10-14 years). 
  2. Cessation of the menstrual cycle – Menopause (occurs at 45-50 years ). 
  3. Reproductive life – 40 years (maximum). 
  4. 1 Menstrual cycle – 28 days (ideally). 
  5. So in 1 year -12 menstrual cycle. 
  6. So in reproductive life, 450 M.C or 450 ova are produced (average)

Hormonal Role 




Menstrual Cycle 


  • Ovarian changes 
  1. Due to FSH and LH
  • Uterine changes
  1. Due to Estrogen and progesterone  

Hormones their source and their roles

  • Estrogen:-
  • Sources:- Theca interna (main), Corpus luteum, Placenta, Membrana granulosa
  • Role:- 
  1. Repairing and growth of the endometrium
  2. Endometrium hyperplasia(increase in the number of cells)
  3.  Myometrium hypertrophy(increase in cell size)
  4. Increases thickness of the uterine wall 
  5. Development of secondary sexual characters 


  • Progesterone(pregnancy hormone or anti-abortion hormone):-
  • Sources:- Corpus luteum, Placenta
  • Role:-
  1. Maintains the thickness of the endometrium
  2. Increases secretory nature of the endometrium
  3. Increases the adhesive nature of endometrium
  4. Decreases the myometrial contractions
  5. Works with estrogens to prepare the endometrium for implantation  

    • Inhibin:-
    • Source:- Membrana granulosa (ovary), Placenta
    • Role:-
    1. Inhibits the release of FSH (mainly) and LH.


    • Relaxin:-
    • Source:- Corpus luteum (ovary), Placenta
    • Role:-
    1. Relaxes the pubic symphysis and dilates the uterine cervix
    2. Inhibits contractions of uterine smooth muscles.  

    Feedback Mechanism


    The Phase of Menstrual Cycle

    • BLEEDING PHASE (4-5 days)

    • Phase:-  A. Initial stage 
    • Hormonal changes:- GnRH, FSH, LH, Estrogen,  and progesterone are low 
    • Ovarian changes:- Complete degeneration of corpus luteum (Corpus Albicans) 
    • Uterine changes:- 
    1. Due to the withdrawal of sex hormone, prostaglandins are formed in the uterus, which causes arteriolar vasoconstriction.
    2. It leads to the decreased blood supply to stratum functional that results in its degeneration and separation.
    3. Prostaglandin also causes contraction of the myometrium which leads to sloughing of dead endometrial tissue (stratum functional) with blood from the uterine cavity through the vagina.
    4.   This bleeding continues up to 4-5 days and clotting does not occur due to the presence of fibrinolytic enzymes.
    5. Average 40 to 80 ml blood loss per cycle.  
    • Phase:-  B. Terminal stage 
    • Hormonal changes:- GnRH↑, FSH↑, LH↑, due to negative feedback of low level of estrogen and progesterone.
    • Ovarian changes:- 6-12 primary follicles are stimulated and start the formation of the secondary follicle. 
    • Uterine changes:-
    1. Uterine bleeding is gradually reduced. 

    • FOLLICULAR/PROLIFERATIVE/ESTROGENIC/PREOVULATORY PHASE.
    • Phase:- A. Initial stage 
    • Hormonal changes:- GnRH↑, FSH↑, LH↑, Estrogen ↑ 
    • Ovarian changes:- 1-2 Secondary follicle ➡ 1 Tertiary follicle.  
    • Uterine changes
    1. Uterine bleeding is stopped. 
    2. Endometrial hyperplasia. 
    3. Formation of stratum functionalis.

    • Phase:-  B. Terminal stage 
    • Hormonal changes:-Estrogen ↑↑➡ FSH surge and LH surge
    • Ovarian changes:- Tertiary follicle➡Mature tertiary follicle (Graafian follicle) 
    • Uterine changes:-
    1. The thickness of the uterine will be increased.
    2. Myometrium hypertrophy.  

    • LUTEAL/SECRET/PROGESTERONIC/POST-OVULATORY PHASE (Fix of 14 Days)
    • Phase:-  A. Initial stage 
    • Hormonal changes:- GnRH, LH, FSH are comparatively low than the terminal stage of the follicular phase.
    • Ovarian changes:- Ruptured Graafian ➡ follicle Corpus hemorrhagic ➡ Corpus luteum (maximum developed on 22nd day)
    • Uterine changes:- 
    1.  More secretory (glandular) nature of endometrium
    2. The thickness of the uterine will maximum (23rd day) 

    • Phase:-  B. Terminal stage 
    • Hormonal changes:- Increased progesterone give negative feedback ➡ GnRH, LH significantly low further decrease of progesterone and estrogen due to degeneration of corpus luteum
    • Ovarian changes:- Corpus luteum degeneration (Corpus Albicans on 28th day
    • Uterine changes:- 
    1. Size of stratum functionalis decrease.
    2. The thickness of the uterine will decrease.
    3. Myometrial atrophy


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    Menstrual disorder 

    Amenorrhea is the absence of a menstrual period in a woman of reproductive age. 


    1. Precocious puberty: Menstruation occurs before the age of 8 years.
    2. Cryptomenorrhea: Occurrence of menstrual symptoms without external bleeding (Collagen deposition on hymen) 
    3. Dysmenorrhoea: Painful menstruation is called Dysmenorrhoea
    4. Menorrhagia:- A normal menstrual blood loss is 50-80 ml, and does not exceed 100 ml. In menorrhagia the menstrual cycle is unaltered but the duration and quantity of the menstrual blood loss are increased
    5. Polymenorrhoea: In polymenorrhoea, the menstrual cycle is reduced from the normal of twenty-eight days to a cycle of two to three weeks and remains constant at that increased frequency


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