Physiology: Endocrine control of ovarian and menstruation + Amenorrhoea

Question 1

Describe the endocrine control of female reproductive axis: hypothalamic-pituitary ovarian axis

Answer 1

1. Starts with GnRH from hypothalamus
2. FSH + LH from anterior pituitary
3. Acts on ovary -> oestrogen + progesterone
4. Positive feedback of oestrogen only happens mid cycle (day 12-14) to cause LH surge needed for ovulation. Rest is negative feedback

Question 2

What are the roles of progesterone, GnRH, FHS and Oestrogen?

Answer 2

Progesterone: maintains secretary endometrium and mediates lobuloalveolar development of breast tissue

GnRH: Stimulates FSH and LH secretion from anterior pituitary

FHS: Stimulates follicular recruitment and development

Oestrogen: Stimulates proliferation of endometrium + positive control of LH surge in late follicular phase + negative feedback control of LH and GnRH. Also ovary not receptive to oestrogen

Question 3

Describe the endocrine control of the ovarian cycle

Answer 3

Follicular phase = FSH causes follicle to mature and produce oestrogen (inhibit development of other follicles)

Ovulation = An LH surge causes ovulation (follicle rupture and releases a secondary oocyte)

Luteal phase = Ruptured follicle forms a corpus luteum and secretes progesterone (and some oestrogen)

Menstruation = when corpus luteum degenerates (forms a corpus albicans) -> new ovarian cycle can begin

Question 4

Amenorrhoea: What are some problems with regulating homrones?

Answer 4

Hypogonadotropic hypogonadism= Low FSH, LH, high prolactin

○ Functional– Excessive weight loss or gain, over exercising, stress
○ Chronic medical conditions- Diabetes, Sarcoidosis, Renal disease, TB
○ Intracranial Space occupying lesion- Prolactinoma, tumours, cysts
○ Infection or Trauma- Meningitis, intracranial bleed, Sheehan’s
○ Drugs: Glucocorticoids, anabolic steroids, opiates
○ Genetic- Kallmann’s syndrome

Question 5

Amenorrhoea: What are some problems with ovarian function?

Answer 5

Hypergonadotropic hypogonadism = high or normal FSH, LH
○ Genetic- Turner’s syndrome(46X), Fragile X
○ Ageing- steep decline in ovarian function past 35 years
○ POF (premature ovarian failure) or POI (primary ovarian insufficiency)
○ Chronic illness- autoimmune diseases
○ Radiotherapy or Chemotherapy
Infection- tuberculosis, mumps oophoritis

Question 6

Amenorrhoea: What are some problems with uterus or outflow tract?

Answer 6

1. Congenital
   - Absent Uterus, vagina- lack of Mullerian duct development(MRKH syndrome)
   - Transverse vaginal septum or imperforate hymen- Mullerian duct fail to canalise
   - Androgen insensitivity syndrome
2. Iatrogenic
   - Uterine adhesions or synechiae (Asherman syndrome)
   - Radiotherapy- Pelvic or cervical