My Clinical Notes

Menstrual Cycle

• In early GnRH from the hypothalamus induces production of FSH by the gonadotrophs of the anterior pituitary
• FSH induces a group of ovarian follicles to start to grow
• By the 12^th day several follicles will have reached 1cm or more but one will be dominant. At this stage GnRH causes secretion of a large quantity of LH
• LH and FSH causes ovulation
• Retained follicular cells become the corpus luteum and secrete large quantities of progesterone and oestrogen
• Failing fertilisation the corpus luteum degenerates around d22

Hormonal control

• GnRH is released in a pulsatile fashion
• Inhibin is produced by the corpus luteum and inhibits production of FSH
• A peak of FHS is reached on the 6^th day of the succeeding menstrual cycle
• This results in increased oestrogen
• This has a negative effect on FSH
• Second peak of FSH occurs just before ovulation at the same time as the LH peak
• Peak is related to the peak of oestrogen which reaches a critical level at day 12. At this time instead of negative feedback it starts to exert positive feedback on the pituitary with a consequent rise in FSH and LH
• LH is present throughout the cycle at low levels apart from the rapid peak with results in ovulation
• 3 main oestrogens ate oestradiol, oestrone and oestriol
• Levels are low doing menstruation and then rise from day 6 to reach a peak at day 12. A fall then occurs followed by a further increase a week later during the maximum activity of the corpus luteum
• Progesterone is almost absent in the early stages of the menstrual cycle. There is a steep rise from the time of ovulation with the peak achieved around day 21. Levels then fall.

Endometrial Cycle

• Early proliferative phase occurs from around day 5. endometrium shows proliferation of glands and stroma
• Late proliferative phase occurs from around day 12, glands become very large and are dilated
• The proliferative phases are under the influence of oestrogen
• Progesterone from the corpus luteum causes the secretory phase. Secretory changes are induced in the glands and the stromal cells swell
• Towards the 28^th day, the stroma becomes even more vascular and oedematous, small haemorrhages and thrombi appear and the endometrium breaks down due to a withdrawl of hormonal support. Menstruation occurs

Menarche

• Normally last manifestation of puberty in the female
• Occurs on average at age 13
• Mechanism involves development of the pulsatile release of GnRH which lead to production of gonadotrophins

Menopause

• Cessation of menstruation
• Oestrogen levels fail over the 5 years preceding ovarian failure
• Occurs on average around 50
• Fall in oestrogen has a positive feedback effect on the pituitary resulting in the production of increased levels of LH and FSH
• May occur early (before age of 45) due to
• Surgical removal of both ovaries
• Radiotherapy
• Chemotherapy
• Unusually small numbers of primordial follicles present at birth
• Smoking – menopause occurs 6 to 18 months earlier

Differential Diagnosis

• Pregnancy
• Polycystic ovary syndrome
• Prolactinoma

Investigations

• Measure LH, FSH and oestradiol on 2 separate occasions, 2 weeks apart

FSH (U/litre)

LH (U/litre)

Oestradiol (pmol/L)

Signs and Symptoms

• Related to circulating changes in oestrogen
• Subjective symptoms may occur before menstruation ceases
• These are;
  • Hot flushes
  • Sweats
  • Palpitations
  • Depression
  • Irritability
  • Emotional lability
  • Decreased libido
• Somatic symptoms include
  • Breast atrophy
  • Dyspareunia
  • Urinary frequency/urgency
  • Osteoporosis
  • Ischemic heart disease
  • Cerebro-vascular disease
  • Changes in the genital tract
    • Main structures reduce in size
    • Fascia and pelvic ligaments become weakened
    • Clitoris shinks
    • Labia majora shrinks
    • Vagina diminishes in length and has reduced secretions
    • Vaginal epithelium becomes atrophic

Treatment

HRT

• Combination of oestrogen and progesterone or a synthetic compound with properties of both (e.g. tibolone)
• Progesterone is not required if a women has had a hysterectomy
• Preparations may be oral, impant, transdermal, nasal sprays and vaginal preparations
• Benefits
  • Reduces risk of oestoporosis
  • Reduced bladder dysfunction
  • Protects against bowel cancer and Alzheimer’s disease

• Complications
  • Breast cancer increased risk
  • Thromboembolic disease
  • Endometrial carcinoma (if oestrogen in unopposed)
  • May cause PMS symptoms and fluid retention

This entry was posted on Saturday, September 29th, 2007 at 4:39 pm and is filed under Gynaecology/Obstetrics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.