Menstrual cycle By Natalie Maltseva

Outline Preparation Ovulation Brief fertility Wait and See

Main facts: Menarche: Beginning of menstrual cycles Menopause: End of menstrual cycles Mean blood loss = 40ml (range ml) Cycle length= first day of bleeding( LMP) in one cycle to first day of bleeding in next cycle Cycle length approx 28 days, (range21-42)

2 parts of the cycle: Ovarian and Menstrual

Phases of menstrual cycle: in the uterus 1. Menstruation 2. Proliferation 3. Secretory Phases of ovarian cycle: in the ovary 1.Folicular phase – (early, middle, late) 2.Ovulation 3.Luteal

Control and Coordination PULSATILE SECRETION of GnRH by the hypothalamus – stimulates anterior pituitary gland Gonadotroph hormones secreted by the anterior pituitary: – Luteinising Hormone acts on theca cells  androgens – Folicular Stimulating Hormone acts on granulosa cells  inhibin and oestrogen Oestrogen secreted by the follicles – pay attention to the different effect at low/hgh levels – -ve feedback (at low levels) on hypothalamus, anterior pituitary – +ve feeback (at high levels in the absence of progesterone) Progesterone secreted by the follicles – Corpus luteum development – Endometrium etc. Inhibin secreted by granulosa cells negatively regulates FSH secretion at the anterior pituitary (This is important – it helps to lower level of FSH whilst LH level will rise – the difference in the levels of LH and FSH are important for Luteal SUrge)

Ovarian cycle 1.Folicular phase – early, middle, late 2. Ovulation 3. Luteal phase

Early Follicular phase Begins as menstrual shedding starts  No corpus luteum present. Follicles are small – Very little oestrogen or inhibin  hypothalamus and pituitary free from feedback inhibition FSH and LH begin to rise  FSH more dramatic (because no inhibin present) FSH binds to granulosa cells, develops follicle to form theca interna. LH binds to theca cells Follicles begin to grow FSH stimulates the granulosa cells (this produces inhibin and oestrogen)

Mid follicular phase Oestrogen dominant Growing follicles secrete oestrogen and inhibin: – FSH falls rapidly compared to LH because of selective action of inhibin. Dominant oestrogen stimulates: – Oviduct motility – Thickening of endometrium – Growth and motility of myometrium – Thin cervical mucous – alkaline – Vaginal secretions – Changes in skin, hair, calcium metabolism.

End of follicular pre-ovulatory phase One follicle becomes dominant Rising oestrogen levels flip into positive feedback (absence of progesterone) LH surge stimulates ovulation. Ovulation timing can be affected by stress and environment

Ovulation : Brief period of fertility begins (approx hours) Ovulation sometimes causes brief mid-cycle pain or bleeding: – PAIN: small amount of fluid passes into the peritoneum as ovum ejected = inflammatory response – BLEEDING: Dut to drop in oestrogen levels  endometrium temporarily loses strength

Luteal phase Disrupted follicle forms corpus luteum  rapid rise in progesterone and also oestrogen levels LH, FSH and GnRH remain suppressed, corpus luteum lasts for 14 days. Dominant progesterone: – Acts on oestrogen primed cells, Further thickening of endometrium into secretory form Thickening of myometrium Thick mucus Changes in breast tissue Increased body temperature.

Luteal phase 2 Corpus luteum programmed cell death after 14 days. Steroid levels fall, endometrium begins to shed. Pituitary and hypothalamus freed from feedback inhibition  FSH and LH start to rise for a new cycle - UNLESS CONCEPTION

IF PREGNANCY IS ANNOUNCED : Developing trophoblast and placenta secrete hCG (human chorionic gonadotrophin) Preserves the corpus luteum until the placenta takes over at weeks.

Endometrium: Stimulated by oestrogen….proliferates Stimulated by oestrogen AND progesterone……. secretory change Conceptus arrives and takes control……or Steroids withdrawn…..flushed away

Menopause: Occurs years, mean age 51. Decline in ovarian oestrogen production  increased FSH & LH. Occurs because degeneration of follicles (atresia) increases from age 35, fertility wanes from age 37, increased risk of miscarriage.

3 stages of menopause: 1. Pre-menopause: – From age 40years – Changes in menstrual cycle  follicular phase shortens – Ovulation early or absent – Decreasing oestrogen – LH&FSH rise (FSH more due to  inhibin) – Reduced feedback. – Leads to reduced fertility  meiotic non disjunction, miscarriage increases 2. Menopause: Cessation of menses. Average but variable. No follicles to develop  oestrogen falls dramatically FSH rises dramatically as no inhibin. 3. Post-menopause:

Symptoms of Menopause: CLASSIC SYMPTOM TRIAD affects 80% – Hot flushes – Sweats – Vaginal dryness Non-specific symptoms: – Headache – Migraine – Palpitations – Disturbed sleep Periods become infrequent (oligomenorrhea) and then cease. Urogenital symptoms – Vaginal dryness – Cystitis – Urinary frequency – Incontinence. Psychologic symptoms – Loss of concentration – Poor memory – Irritability – Loss of libido – Panic attack. Atrophy of connective tissue – Skin thinning, hair loss, brittle nails, aches & pains. Osteoporosis – loss of bone matrix (esp vertebral column), loss of height, deformity, fractures.