ib 140 lec 7

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ib 140 lec 7
2010-04-01 13:24:17
ib 140 lec 7

ib 140 lec 7
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  1. Reproductive aging
    • • Males can produce viable spermthroughout their adult life, although itdiminishes with age, however, thereare cases of men fathering children well into their 90s
    • • Females typically go through menopause around age 50 years andno longer have viable follicles and cannot reproduce
  2. Paternal age and fertility
    • • At age 24, the probability of aman to produce a pregnancywithin a year of frequent (≥ 3times/week), unprotected coitusis about 92%
    • • This probability decreases about3% for every subsequent year
  3. Paternal age & chromosomalabnormalities
    • • Aneuploidy and other chromosomalabnormalities occur during meiosis inthe testes and these abnormalitiesincrease with paternal age
    • • Likely that these abnormal sperm havea reduced ability to fertilize an egg
    • • Increase rates of miscarriages inpregnancies from fertilization by spermfrom older men
    • • Decreased IQ and cognitive abilities inoffspring of older fathers
    • • Increase rates of autism in offspring ofolder fathers
  4. Andropause: hormonal changes
    • Andropause symptoms emergegradually over decades typicallystarting in late 40s andextending until 70 (compared towomen whose menopause iscomplete within a few months oryears)
    • • Gradual decline in testosterone at a rate of 1%per year after age 40 in men
    • • During this time the number of Leydig cellsreduces in the testes
    • • Appears to be a reduction in the testes ability torespond to gonadotropins
    • • Blood supply to testes is also reduced
    • • Seminiferous tubules show damage in some oldermen
    • • Semen volume, sperm motility and viability alldecrease with age
    • • Blood levels of estrogen may rise in older men
  5. Andropause signs & symptoms
    • • Erections may require more foreplaystimulation
    • • Voice may rise a pitch
    • • Facial hair growth may decrease
    • • Scrotum & penis may reduce in size
    • • Seminal vesicles and other accessorystructures may reduce in size (however,prostate can enlarge and develop benignprostatic
    • hyperplasia)
    • • Decreased muscle mass and strength
    • • Osteoporosis may develop
  6. Menopause
    • Menopause is the permanent end ofmenstrual cycling and menstruationassociated with dramatic reduction orloss of ovarian follicular activity
    • • Ovaries go through an abrupt decline,resulting in degeneration of theirfunction
    • • Menopause occurs between 45-55years with average age of 52 years inUSA
    • • Clinical diagnosis of menopause isdefined when a woman in this agerange has had no menstrual cyclesfor at least one full year
    • • Possible for women to ovulate for up to oneyear after menopause has occurred
    • • Women can still have eggs and folliclesafter going into menopause, however, thefunction of the follicles and the number ofeggs are both dramatically diminished
    • • As women age and go though menopause,there is a dramatic reduction in both thenumber and average quality of eggs
    • • As follicles deteriorate, the egg supply isdiminished, which leads to infertility
  7. Female reproductive stages (Table 7-1)
    • • Prereproductive
    • • Early reproductive:
    • menstrual cyclesvariable to regular; FSH normal
    • • Peak reproductive:
    • menstrual cyclesregular; FSH normal
    • • Late reproductive:
    • menstrual cyclesregular; FSH elevated
  8. • Low estradiol → lack of negative feedbackon GnRH → increased FSH & LH levels

    • Decline in inhibin also results in ↑FSH

    • In women in menopause, the FSH is 10times and the LH is 4 times higher than inyounger women

    • Decrease in GnRH pulse frequency in menopause