Physiology of Menstrual Cycle.

These notes describes menstrual cycle changes includes endocrine changes, endometrial wall changes and changes follicles inside ovary.

1. PHYSIOLOGY OF THE MENSTRUAL CYCLE 1

2. OUTLINE : Introduction Definition Characteristics of Normal Menstruation The Hypothalamic-pituitary-ovarian Axis Ovarian Cycle Uterine Cycle Menstrual Abnormalities Comfort Measures During Menstruation 2

3. INTRODUCTION Typically, a woman of childbearing age or reproductive age ( 15-45 ) should menstruate every 28 days or so unless pregnant or in menopause. Numerous things can go wrong with the normal menstrual cycle. The menstrual cycle is essential for the production of ova , and for the preparation of the uterus for pregnancy . 3

4. DEFINITION Menstruation is the periodic discharge of blood, mucus and uterine cellular debris at cyclic intervals from menarche to menopause . A.K.A: Period, Menses, Menstrual bleeding. Exception: Pregnancy, Lactation, Anovulation, Pharmacological Interventions e.g. contraceptive pills. 4

5. CHARACTERISTICS OF N.M Menarche: 10–16 years (Average: 13 years). Duration: 2–7 days. <2 days – Hypomenorrhea >7 days – Menorrhagia Amount: 30–80 ml. Uses 3 napkins/pads per day <30ml – Hypomenorrhea >80ml – Menorrhagia Cycle length: 21-35 days (Average: 28 days). 5

6. CHARACTERISTICS OF N.M CONT. Normal menstrual blood doesn’t coagulate as a result of secretion of fibrinolysin enzyme ( plasmin ) secreted by the endometrium. Menstrual molimina refers to mild symptoms of 7-10 days before menstruation relieved once menstruation occurs exaggerated condition called Premenstrual Syndrome . 6

7. NOTE: Menopause: 45 – 55 years (Average: 51 years). Factors such as hereditary, diet and overall health can accelerate or delay menarche. Irregular menstrual cycle is when the cycle length is <21 days or >35 days. 7

8. CHARACTERISTICS OF N.M CONT. 8

9. THE HYPOTHALAMIC- PITUITARY-OVARIAN AXIS The phases of the MC and ovulation are regulated by interaction between hypothalamus, anterior pituitary and ovaries. The interaction involves hormones. ENDOCRINE GLAND HORMONES Hypothalamus Gonadotropin Releasing Hormone (GnRH) Anterior Pituitary Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). Ovaries Estrogen and Progesterone 9

10. 10 Female HPG axis

11. PHASES OF MENSTRUAL CYCLE There are two main components of the menstrual cycle, the changes that happens in the ovaries ( Ovarian Cycle ) and the variations that take place in the uterus ( Uterine Cycle ). The ovarian cycle is divided into three phases; Follicular, Ovulatory and Luteal . The uterine cycle into three phases; Menstrual, Proliferative and Secretory . 11

12. COMPONENTS OF MENSTRUAL CYCLE 12

13. 13 FOLLICULAR PHASE OVULATOTY PHASE LUTEAL PHASE OVARIAN CYCLE

14. A. FOLLICULAR PHASE Follicular phase begins with menses on first day of the menstrual cycle and ends with ovulation( Day 1 to Day 14 of 28-days cycle) . At the beginning of menstrual cycle, GnRH (pulsatile manner) ➤ FSH and LH. FSH is responsible for the recruitment and growth of several primordial follicle . Only one follicle on one of the ovaries reaches maturity (Graafian follicle) which secretes estrogen. 14

15. A. FOLLICULAR PHASE CONT. Increase in estrogen level causes: Negative feedback on the pituitary to stop FSH The uterine lining (endometrium) to grow thicker 15

16. B. OVULATORY PHASE The estrogen peak stimulates secretion of LH, leading to the LH peak which leads to the follicle to burst open, releasing the mature ovum, a process called ovulation . The remaining Graafian follicle forms Corpus luteum . Ovulation occurs on day 14 of a 28-day cycle. High estrogen also suppress FSH secretion so no further follicles grow. 16

17. C. LUTEAL PHASE After ovulation, LH levels remain elevated and cause the remnants of the follicle to develop into a yellow body called the corpus luteum . In addition to producing estrogen, the corpus luteum secretes a hormone called progesterone. When progesterone reaches a high level it inhibits the secretion of LH leads to degeneration of the corpus luteum (If fertilization does not take place). 17

18. C. LUTEAL PHASE CONT. Degeneration of corpus luteum leads decrease in e strogen and progesterone level and separation of the endometrium (menstruation). Decrease in estrogen and progesterone level stimulates the hypothalamus to secrete more GnRH, a new cycle is started . If fertilization and implantation occurs, placenta secretes human chorionic gonadotropin hormone ( hCG ) which stimulates and maintain the corpus luteum. hCG leads to positive urine pregnancy test. 18

19. 19 MENSTRUAK PHASE PROLIFERATIVE PHASE SECRETOTY PHASE UTERINE CYCLE

20. A. MENSTRUAL PHASE First day of the menstrual cycle is marked by the onset of menstruation (period) . During the menstrual phase of the uterine cycle, the uterine lining is shed because of low levels of progesterone and estrogen. At the same time, a follicle is beginning to develop and starts producing. The menstrual phase ends when the menstrual period stops on approximately day 5. 20

21. B. PROLIFERATIVE PHASE When estrogen levels are high enough, the endometrium begins to regenerate. Estrogen stimulates blood vessels to develop. The blood vessels in turn bring nutrients and oxygen to the uterine lining, and it begins to grow and become thicker . The proliferative phase ends with ovulation on day 14. 21

22. C. SECRETORY PHASE After ovulation, the corpus luteum begins to produce progesterone. This hormone causes the uterine lining to become rich in nutrients in preparation for pregnancy . Estrogen levels also remain high so that the lining is maintained. If pregnancy doesn’t occur, the corpus luteum gradually degenerates, and the woman enters the ischemic phase of the menstrual cycle. 22

23. C. SECRETORY PHASE Ischemic Phase - on days 27 and 28, estrogen and progesterone levels fall because the corpus luteum is no longer producing them. Without these hormones to maintain the blood vessel network, the uterine lining becomes ischemic . When the lining start slough, the woman has come full cycle and is once again at day 1 of the menstrual cycle. 23

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25. OTHER PHYSIOLOGICAL CHANGE CERVICAL MUCUS CHANGE BASAL BODY TEMPERATURE 25

26. A. CERVICAL MUCUS CHANGES Changes in cervical mucus takes place over the course of the menstrual cycle. Some women use these characteristics to help determine when ovulation is likely to happen. During the menstrual phase the cervix doesn’t produce mucus. As the proliferative phase begins, the cervix begins to produce a tacky, crumbly type of mucus that is yellow or white . 26

27. A. CERVICAL MUCUS CHANGES As the time of ovulation becomes near, the mucus becomes progressively clear, thin and lubricative, with the properties of raw egg white. At the peak of fertility(i.e., during ovulation), the mucus has a distensible, stretchable called spinbarkheit . After ovulation the mucus becomes scanty, thick, and opaque. 27

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29. B. BASAL BODY TEMPERATURE Basal body temperature (BBT or BTP) is the lowest body temperature attained during rest (usually during sleep). It is usually estimated by a temperature measurement immediately after awakening and before any physical activity has been undertaken. Monitoring BBTs is one way of estimating the day of ovulation 29

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31. MENSTRUAL ABNORMALITIES Anovulation Dysmenorrhea Hypomenorrhea Metrorrhagia Oligomenorrhea Amenorrhea Polymenorrhea 31

32. MENSTRUAL ABNORMALITIES Amenorrhea (no periods) is the absence of uterine bleeding for more than 6 months in non-menopausal women. Dysmenorrhea (painful periods) is the painful menstruation, typically involving cramps. Hypomenorrhea is the regular menstruation occurring at normal intervals, but with minimal blood loss. Menorrhagia/Hypermenorrhea is the regular menstruation occurring at normal intervals, but with heavy blood loss. 32

33. MENSTRUAL ABNORMALITIES Menometrorrhagia is the uterine bleeding occurring at irregular intervals, with heavy (>80mL) or prolonged (>7days) menstrual flow. Oligomenorrhea is the uterine bleeding occurring at intervals of 35 days or longer (every five weeks or more). Polymenorrhea is the uterine bleeding occurring at intervals of 21 days or less (every three weeks or less). Postmenopausal bleeding is the uterine bleeding that occurs after menopause. 33

34. MENSTRUAL ABNORMALITIES Premenstrual syndrome (PMS) is the physical and psychological symptoms that occur before the start of a period. Primary amenorrhea is absence for uterine bleeding ever starting (at puberty). Secondary amenorrhea is absence of uterine for more than 3 months after menarche. 34

35. CARE AND COMFORT MEASURES Menstrual hygiene: Sanitary pads and tampons: Wash hands before and after giving self-perineal care. Washing or wiping the perineum should be always done from front to back. Reduce use of tampons by substituting sanitary pads especially at night. Use tampon only for heavy menstrual flow. 35

36. CARE AND COMFORT MEASURES Menstrual hygiene: Vaginal spray and douching: Spray should be used externally only not with pads. Should not be applied with broken irritated or itched skin. Douching washes away the natural mucus and upsets the vaginal ecology, thus make it liable to infection. 36

37. REFERENCES Dutta, D.C. and Hiralal Konar (2016).  DC Dutta’s textbook of gynecology : including contraception . New Delhi: Jaypee Hall, J. (2015).  Guyton and Hall textbook of medical physiology.  Elsevier. Wikipedia Contributors (2019).  Menstrual cycle . [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Menstrual_Cycle . All Image from google.com /images 37

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