Male and female reproductive endocrinology Flashcards
Sperm production hormone regulation
- Hypothalamus secretes GnRH.
- GnRH acts on anterior pituitary gland
- Secretion of FSH and LH from gonadotrophes - LH acts on testes to secrete testosterone.
- Testosterone and FSH acts on testes to produce sperm.
Feedback regulation of sperm production
Inhibition of GnRH, LH and FSH
- Testosterone
- Inhibin [though not clinically relevant]
Testosterone effects [8]
Secreted in male embryo from testes
- Causes development of male fetal anatomy.
Puberty= secretion increases significantly
- Causes make sexual characteristics
Acne- increased activity of sebaceous glands
Bone growth- Long bone growth [converted from oestradiol]
Sperm production
Muscle development- androgens are anabolic
Maturation of the genitalia
Male pattern pubic hair growth [facial hair, chest hair]
Enlargement of larynx [voice break]
Main: increased aggression and libido
Development of female anatomy
Caused by no influence of testosterone
- Lack of male hormone= development of female anatomy.
An embryo with XY chromosome without secretion of testes= development of female anatomy
Oestrogen does not influence the development of the fetus
Ovulation regulation
- Hypothalamus secretes GnRH
- In a pulsatile fashion
- The frequency of the secretion determines FSH or LH secretion.
2 GnRH stimulates anterior pituitary to secretion FSH and LH.
- LH stimulates the ovaries to produce progesterone.
FSH stimulates the ovaries to produces oestrogens [oestradiol]
Oestrogens feedback to suppress FSH secretion
Progesterone feedback to suppress LH secretion.
Development of the female during puberty [8]
Significant exposure to oestrogen production at puberty:
Long bone growth
Female psyche
Fair complexion
Breast development
Widening of pelvis
Maturation of genitalia
Female pattern pubic hair: no facial hair, chest hair etc
Subcutaneous fat deposition
Pulsitility of the hypothalamus
The hypothalamus secretes GnRH in a pulsatile fashion.
- Determines if FSH or LH is secreted.
The pulsatility is inbuilt at birth
- Determines the length of menstrual cycle.
If exposed to testosterone, female will lose pulsatility and have a constant secretion of GnRH
- No menstrual cycle.
Menstrual cycle
- 1-7
Menstruation
- FSH levels rise- stimulates a rise in oestrogens
Menstrual cycle
- Day 12-14, until 28
Surge in LH and FSH
- FSH secretion has no function
LH causes increase of oestradiol and progesterone secretion
- Occurs for 7 days then falls off until day 28.
- Progesterone is significantly higher in concentration.
Menstrual cycle
- Day 7-12
- Oestrogens negatively feedback to FSH, causing depletion in FSH.
- Depletion of FSH = depletion of Oestradiols
- Big variation in oestradiol concentration mid-cycle.
- When progesterone and oestradiol levels are very low, this makes testosterone dominant [causes acne]
FSH effects on follicles
Causes follicle to mature and secrete oestrogens.
LH effects on follicles
Causes egg to be expelled, around day 14.
- Occurs after LH surge [Day 12]
After egg is expelled, progesterone released from corpus luteum.
Progesterone and oestradiol on endometrium
Oestradiol causes growth and thickening the endometrium.
Progesterone causes the endometrium to enter the secretory phase.
- Provides conditions to allow ovum to grow.
If fertilisation does not occur
- Progesterone declines and stops secretory phase
- Causes collapse in endometrium.
Drop in progesterone
Occurs last 7 days of menstrual cycle, when fertilisation does not occur.
- Stops secretory phase
- Causes vasodilation of arterial supply to endometrium= tissue death and atrophy
Blood vessels then dilate to increase blood supply
- Blood washes over dead tissue and causes blood clot.
Blood clot is then broken down= bleeding in menstruation.
Pain in menstruation
As tissues die during vasoconstriction, prostaglandins are released.
- Causes smooth muscle contraction= uterine contraction
Combatted by NSAIDs
