Normal Menstrual Cycle

23.2.06

Female patient: check menstrual history.

Menstrual cycle
• Dynamic relationship between hypothalamic, pituitary and ovarian hormones.
• Hypothalamus-pituitary-ovarian axis.
• Uterine changes.
• End result - menses/pregnancy.

Hypothalamus
• GnRH - pre-optic area.
(Kallman syndrome - anosmia/hypogonadotrophic hypogonadism.)
• Nutrition (amino acid level/anorexia).
Stress (CRH/beta endorphins).
Light (serotonin/melatonin synthesis).
• Ventromedial/arcuate nucleus of medio-basal hypothalamus may be pulse generator.
• GnRH - peptide hormone - receptors in anterior pituitary gonadotrophs.
• Pharmacology.
-Analogues = high affinity/longer binding.
-Stimulation > desensitisation.
• Artificial menopause.
-Pre-follicle stimulation in IVF.
-In hypogonadotrophic hypogonadism.

Pituitary
• FSH/LH.
• Feedback regulation with E2/progesterone/inhibin.
• Pulsatile production in response to GnRH pulses - frequency/amplitude.
• Tumours.

FSH
• Antrum formation.
• Gonadotrophin-dependent phase.
• Induce oestrogen production by dominant follicle.
• Induce LH receptors in granulosa cells.
• Used to induce follicle in IVF.

LH pulses - frequency/amplitude
• Pre-ovulatory - highfrequency/low amplitude.
• Mid-cycle - ovulation induction.
• Post-ovulatory - low frequency/high amplitude - ?needed for normal corpus luteal function.
• Used as depot, inhibits ovulation.
• Injection in late follicular phase induces ovulation.

Ovarian hormones
• Theca (LH) and granulosa (FSH) cells - "two cells theory."
• Theca cells produce androgens.
• Granulosa cells = oestrogen, progesterone, inhibin, activins, IGF.

Ovary
• Oestrogen.
• Progesterone.
• Inhibin (inhibits FSH)/activins (stimulates FSH action).
• IGF.
• Chromosome XO (Turners).
• Deletion of part of X → premature menopause.
• PCOS (theca cell hyperplasia) → high androgens, small follicles.

Oocytes
• Dorsal aspect of yolk sac.
• Primordial follicles - 5x106.
• Intermediary/primary follicles - 1x106 at birth.

Secondary follicles
• Antral stage/recruitment.
• Selection of dominant follicle (most sensitive to FSH).
• Ovulation.
• Corpus luteum.
• Corpus albicans.
• Menopause.

Ovulation
• Trigger LH surge (38 hours preceding ovulation).
• Pre-ovulatory E2 surge induces LH surge.
• LH → LHR → second messenger systems.

Puberty
1. Breast growth.
2. Pubic hair growth.
3. Axillary hair growth.
4. Growth spurt.
5. Menarche.

Precautious puberty - primary amenorrheoea.

Endometrium
• Functional layer and basal layer.
• Glandular/stromal/leucocytes/blood vessels.
• Progesterone and oestrogen receptors.
• Prostaglandins/cytokines/chemokins.
• Proliferative phase.
-Oestrogen dominant.
-Stromal and glandular mitosis.
• Secretory phase.
-Progesterone dominant.
-Decidualisation of stroma.
• Menstrual shedding and regeneration.
-Vascular regeneration.

• Menorrhagia - endocrinological/anatomical/iatrogenic.
• Oligomenorrhoea - endocrinological/PCOS/pituitary tumours.
• Amenorrhoea - chromosomal/anatomical/weight/physiological.
• Dysmenorrhoea - endometriosis.
• Pre-pubertal - low oestrogen/no follicular growth.
• Menopause - increased gonadotrophins.