Endocrinology of menstrual cycle Flashcards
What are the 3 types of combined hormonal contraceptives?
Oral contraceptives, transdermal patch, vaginal ring
What does CHC do?
Inhibit ovulation
How is ovulation inhibited?
Oestrogen and progesterone components which act on hypothalami-pituitary axis to reduce LH and FSH production
What does oestrogen do?
Causes endometrium to proliferate and grow
What does progesterone do?
Prevents hyperplasia of endometrium by opposing proliferative effects of oestrogen
What does HPG stand for?
Hypothalamus-pituitary gonad axis
What does GnRH stand for?
Gonadotropin releasing hormone
What does FSH stand for?
Follicle stimulating hormone
What does LH stand for?
Luteinising hormone
What does GnRH do?
LH and FSH production
Where is GnRH released from?
Hypothalamus
What do LH and FSH do?
Act on ovarian follicles and corpus luteum
Where are oestrogen and progesterone produced?
Ovarian follicles and corpus luteum
Which tissue is responsible for menstrual flow?
Endometrium
Which structure controls luteal phase?
Corpus luteum
What are the three phases of the menstrual cycle?
Menstrual phase: flow occurs
Proliferative phase: cells proliferating
Secretory phase: lots of secretions occurring n endometrium, very thick, ready for fertilisation
Lifecycle of primordial follicle
Primordial follicle (13-50 years)
Primary follicle (45 days)
Secondary follicle
Graafian follicle
What happens in pre-ovulation follicular phase?
Hypothalamus makes GnRH Ant. pituitary makes FSH and LH Acts on ovary to develop follicle Inhibin and low levels of oestrogen Negative feedback effect on ant. pituitary
How does hypothalamus decrease FSH concentration?
Hypothalamus stimulates pituitary to produce FSH and LH, stimulates oestrogen production. Not allowing production of other hormones. Action of oestrogen and inhibin increases oestrogen, decreases FSH
What happens in late follicular phase?
Increased production of oestrogen
Graphian follicle
Hypothalamus - GnRH - ant. pituitary - FSH and LH - stimulates Graphian follicle
LH surge produces ovum from follicle
No FSH peak needed but inescapable
Inhibit acts on ant. pituitary = negative feedback
FSH smaller because of inhibin
Where is most progesterone produced?
Corpus luteum
when will follicle become CL?
After ovulation
What happens in luteal phase?
Hypothalamus produces GnRH LH and FSH from ant. pituitary Makes uterus favourable for egg Progesterone high - low FSH and LH CL formed CL makes progesterone and oestrogen - negative feedback on hypothalamus and pituitary
How is fertilised egg maintained?
CL maintained by hCG released from chorion which maintains until placenta takes over
What are ovarian follicles?
Ovaries made of sacs called ovarian follicles. They contain oocyte and cells that produce oestrogen and progesterone
Flow chart of follicle changing to ovulation
Primordial follicle - primary follicle - secondary follicle - Graafian follicle - ovulation
How is anterior pituitary connected to hypothalamus?
Vascular
How is posterior pituitary connected to hypothalamus?
Neuronal
LH surge
Re-starts meiosis in oocyte
Follicle ruptures - ovulation - oestrogen production reduced
What happens when no fertilisation occurs?
No hCG so CL degenerates
Progesterone and oestrogen lost
Vasoconstriction - tissue death
Dysmenorrhea
Painful periods
Menorrhagia
Heavy/prolonged periods
Amenorrhea
Absence of periods
Oligomenorrhea
Light periods
Combined pill
Low oestrogen: no FSH - no follicles - nothing to ovulate
Progestogen: decreases LH, decreases GnRH
Progestogen-only pill
Cervical mucus inhospitable to sperm
Hinders implantation
Breakthrough bleeding/irregular periods
