Menstrual Cycle

Fawaz EdrisMD, FRCSC, FACOG, RDMS, AAACS

Maternal Fetal Medicine

Reproductive Endocrinology & Infertility

Introduction

Hypothalamus – Pituitary – Ovaries - Endometrium Hormonal changes functional and morphological

changes in ovaries ovulation endometrial changes implantation or menstruation

Hypothalamus – pituitary axis Menstrual Cycle = Ovarian + Endometrial + Cervical

+ Vaginal + Breast + Psychological + Others

Ovarian Cycle

Estrogen. Estrdiol (Ovary - Follicles) + Estrone (Androstendione –

Aromatization)

Low in early proliferate phase Rise 1 week before ovulation Maximum 1 day before LH surge Marked drop Rise again to its maximum 5-7 days after

ovulation (mid-luteal) Baseline before menstruation

Ovarian Cycle

Progestins. Progesterone (conversion from adrenal pregnenolone +

pregnenolone sulphate) + 17-OHP Minimal during follicular phase Just before ovulation start to increase (from lutenized

graafian follicle) – Hence need for LH/hCG during IVF Rise to its maximum 5-7 days after ovulation (mid-luteal) –

elevated BBT Baseline before menstruation If pregnancy continue

Ovarian Cycle

Androgens Directly (small amount) from ovaries + adrenals Indirectly (most amount) (metabolism from

Androstenedione from ovaries & adrenals) SHBG

Binds most Estrogens & Androgens Prolactin

Levels do not change strikingly during cycle

Follicular Development Primordial follicles (development – differentiation –

maturation) Mature graffian follicle(s) produced Follicle rupture and release ovum Ruptured follicle luteinize and produce corpus luteum

Follicular Development During each cycle a cohort of follicles are recruited

One usually mature (18-25mm) – remain go into atresia Mature follicle is estrogen dependent

Increase local FSH – continue to grow despite drop of mid-follicular FSH FSH enhance FSH receptors increased E2 enhance FSH &

LH receptors LH enhance androgen aromatization to E2 LH receptors increase the response to mid-cycle LH surge which is

important for final maturation, ovulation, and luteal progesterone production

Atresic follicles are androgen dependent Decreased local FSH – cant grow LH induced androgen will not aromatize and will lead to

atresia

Ovulation LH surge structural and biochemical changes to

the growing follicle(s) Dissolution of the entire follicular wall particularly at the

surface of the ovary takes place (proteolytic enzymes) Detachment (less attachment) of the oocyte along with the

cumulus from the remain of the follicle Oocyte adheres to the surface of the ovary for

extended time allowing fallopian tube contractions to bring the ovary into close contact with the tubal epithelium

Tubal muscular contraction +/- tubal cilia movement contribute to the entry of & transportation of the ovum along the tube

Ovulation

At birth, primary oocyte are in the prophase of first meiotic division

Few hours before ovulation, meiotic division takes places, and secondary oocyte along with a polar body are produced (each 23 chromosomes)

After fertilization, second polar body is formed

Corpus Luteum

LH granulosa cells of ruptured follicle undergo luteinization

Luteinized granulosa cells + surrounding theca cells + capillaries + CT CL

CL ++++ progesterone & + E2 Life span of CL = 9 - 10 days (unless

pregnant) corpus albicans (avascular scar)

Endometrial Cycle Endometrium is responsive to Progestins +

Androgens + Estrogens menstruation & implantation & pregnancy

Functionally the endometrium is divided to 2 zones: Outer portion (functionalis)

Cyclical changes in morphology & function during menstrual cycle

Sloughed off during menstruation Occupied by spiral arteries (coiled)

Inner portion (basalis) Relatively unchanged during menstrual cycle Provide stem cells for the renewal of the funcionalis Occupied by basal arteries (straight)

Endometrial Cycle

Histophysiology of the endometrium is divided into there stages: Menstrual phase Proliferative or estrogenic phase Secretory or progestational phase

Menstrual Phase

First day of menstruation is day 1 of the cycle Last 4-5 days

Disruption and disintegration of the endometrial glands & stroma

Leukocyte infiltration RBC extravasaion

Sloughing of the funtionalis Compression of the basalis Renewed tissue growth within the basalis

Proliferative Phase

Endometrial proliferation or growth secondary to estrogenic stimulation

By the end of this stage: Cellular proliferation & endometrial growth

reached maximum Numerous mitotic activity Spiral arteries are elongated and convoluted Endometrial glands are straight with narrow

lumen containing glycogen

Secretory Phase Following ovulation progesterone secretion by CL stimulates

the glandular cells to produce glycogen, mucus, and others Glands become tortuous and filled Stroma become edematous Mitosis are rare Spiral arteries extend into superficial layer If pregnancy doesn’t occur by day 23

CL regress Secretion of Progesterone and E2 decline Endometrial involution 1 day before menstruation, marked constriction of spiral arteriols takes

place ischemia of endometrium lukocyte infiltration & RBC extravasation Prostaglandin effects

Pain

Cervical Cycle

Although part of the uterus but different in many ways: The mucosa does not undergo cyclical desquamation Instead there are changes in the cervical mucus

Estrogen makes it thinner and alkaline Thinnest at ovulation time (spinnbarkeit 8-12cm) Promote sperm survival and transport

Progesterone makes it thicker and cellular Histologically

Estrogen gives it fern like pattern After ovulation & during pregnancy fail to fern

Vaginal Cycle

Estrogen Cornified epithelium

Progesterone Thick mucus secretion Epithelial proliferation Infiltration by leukocytes

Breast Cycle

Estrogen Proliferation of the mammary ducts

Progesterone Growth of lobules and alveoli

Distention of the ducts + hyperemia and edema of the interstitial breast tissue Breast swelling, tenderness, and pain

Starts 10 days before menstruation and disappears with menstruation

Other Cyclical Changes

Temperature Progesterone

Emotional Psychological

Thank you