03. Menstruation Flashcards
Two general phases of Menstrual & Ovulatory Cycles
Follicular phase & Luteal phase
Hormone surges during Follicular Phase (in order)
FSH & LH (minor surge); Estrogen surge; LH surge; FSH surge
Hormone surges during Luteal Phase (in order)
Progesterone (major) & Estrogen (minor surge)
Follicular Phase Characteristics
Begins at onset of menses; Ovarian follicle recruitment & maturation; Ends with pre-ovulatory surge of LH stimulating ovulation (24-36 hr at end)
Luteal Phase Characteristics
Begins with ovulation; Ends at onset of menses; Endometrium thickens in preparation for pregnancy; Ends in pregnancy or luteolysis
Estimated blood loss during menses
~30 cc
Excessive blood loss during menses
~80 cc
Period of heaviest blood loss during menses
First 2 days
FSH effects
Causes 15-20 eggs to begin maturing in each ovary; Follicles produce estrogen
Estrogen effects
Released by maturing follicles; when threshold is reached, follicle is mature and triggers LH surge
LH Effects
Triggered by high estrogen levels; Causes egg to burst from follicle; Stimulates ovary to produce progesterone after ovulation. Also stimulates follicles to produce androgens, which are converted to estrogen
Progesterone Effects
Produced by corpus luteum; Prevents release of all other eggs for that cycle; Causes thickening of endometrium & sustains life until corpus luteum distintegrates (12-16 days later); Causes changes in 3 fertility signs
What are the 3 fertility signs?
Change in temperature, cervical fluid, and cervical position
3 Major Components that Regulate the Menstrual Cycle
Hypothalamic/Pituitary Axis; Ovaries; Endometrium/Uterus
5 Small Peptides/Amines From Hypothalamus that affect Reproductive Cycle
GnRH; TRH; SRIF; CRF; PIF (Prolactin release-inhibitin factor)
GnRH Effects
Pulsatile release from hypothalamus; Increased during follicular phase; Decreased during luteal phase; Pulses q90min; To the ANTERIOR PITUITARY via portal circulation;
Negative Estrogen Feedback Mechanism
During early follicular phases, estrogen levels low
Positive Estrogen Feedback Mechanism
High concentrations at end of follicular phase trigger FSH & LH, which trigger increased estrogen release; Ensuring LH surge triggers ovulation
Follicle count of 20 week fetus
6 million
Follicle count of newborn
600,000
Follicle count at menarche
300,000
Follicle count at menopause
10,000
FSH & LH negative feedback
High levels of estrogen and progesterone during luteal phase suppress FSH & LH
What is the time span between the LH surge and ovulation?
24-36 hr
Days 1-4 of menstrual cycle
“Bleeding phase”; Estradiol & progesterone levels low; FSH begins to rise; LH begins rising days after FSH starts rising
Causes of uterine sx during menstruation
Corpus luteum involutes; Prog & est fall rapidly; Prostaglandins increase in myometrium to stimulate contraction
Days 4-14 of menstrual cycle
Follicular phase; Estradiol increases & peaks just before LH surge & ovulation; Progesterone stays low; FSH peak mid-cycle with LH, but in lesser surge; LH rapidly peaks mid-cycle & triggers ovulation
Day 12-14
Ovulation; mid-cycle between follicular & luteal phases
Uterine changes during luteal (secretory) phase
Progesterone stimulates glands to secrete mucus & glycogen; Glands become tortuous & dilated; Convoluted spiral arteries extend to superficial layer of endometrium;
Corpus luteum
Forms from the granulosa cells of the ruptured follicle; maintains pregnancy until placental progesterone production is adequate
What happens to the corpus luteum if pregnancy doesn’t occur?
It degenerates intoa corpus albicans, which causes regression of progesterone and estradiol levels.
Estrone
Hormone secreted by ovary & adrenal glands; converted to estrogen in peripheral fat to maintain vaginal tissue, minimize hot flashes/night sweats/mood swings
Which hormone remains elevated if pregnancy occurs?
Progesterone
What are negative effects of high prolactin levels?
Interfere with FSH/LH and may cause anovulation. This is why people think they can’t get pregnant while breast feeding.
How can hyperthyroidism cause infertility?
High TSH levels stimulate Prolactin production. High prolactin levels lead to anovulation, which results in infertility.
How can adrenal dysfunction lead to infertility?
High ACTH inhibits FSH & stimulates androgen production. In combo, this inhibits ovulation.