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Which came first - the chicken or the egg?�Physiology of Reproduction�

Jennifer McDonald DO

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Hypothalamic Pituitary Axis

Neural control

Chemical control

Dopamine

(-)

Norepiniphrine

(+)

Endorphins

(-)

Hypothalamus

Gn-RH

Ant. pituitary

FSH, LH

Ovaries

Uterus

Progesterone

Estrogen

Menses

–

±

?

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Sequence of Maturation

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Telarche = breast development

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Estrogen dominant

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Tanner Staging - Breast Development

Prepubertal

Breast bud with areola widening

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Enlargement of breast. No separation of contours

Secondary mound with separation of contours

Mature breast

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Adrenarche = pubic hair growth

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Adrenal androgen dominant

DHEA

DHEAS

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Tanner Staging - Hair Growth

No hair

Straight along labia

Increased quantity, female triangle

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More dense, curled, adult distribution

Medial aspect of thighs

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Timing is Everything

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Menarche = onset of menses

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Average 2 to 2.5 years after breast development

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Average American girls 12.7 years +/- 1 year

Earlier in African American and Hispanic girls

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Usually delayed until critical mass ~105 pounds or body fat content of 22%

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Delayed Puberty

  • No pubertal development by age 13

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  • Pubertal maturation not completed within 4 years or

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  • Menses not begun by age 16

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Precocious Puberty

  • Breast or pubic hair development before 7 years (Caucasians) or younger than 6 years (African Americans)
  • Most common cause = idiopathic

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Menarche

Requirements:

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    • GnRH from the hypothalamus
    • FSH and LH from the pituitary
    • Estrogen and progesterone from the ovaries
    • Normal outflow tract

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Who’s Doing What

Ovary

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Follicular Phase

Ovulation

Luteal Phase

Uterus

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Proliferative Phase

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Secretory Phase

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Mature Ovary

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Non-growing = primordial follicles

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Growing follicles

Primordial follicles are arrested in which stage of meiosis?

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Numbers Game

15 to 20 weeks gestation as many as 7 million germs cells in each ovary

Newborn = 2 million primary oocytes

Puberty = 300,000 primary oocytes remain

400 will become secondary oocytes and ovulate during reproductive years

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GnRH

Gonadotropin releasing hormone

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Comes from ??

Stimulates ??

What is unique about its release ??

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Follicle Stimulating Hormone (FSH)

Comes from ??

Release stimulated by ??

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  • Stimulates growth and maturation of follicles
  • Stimulates estrogen production in granulosa cells
  • Inhibited by estrogen and progesterone

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Theca interna - androstenedione in response to LH

Granulosa cells - convert androstenedione to estradiol when stimulated by FSH

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Luetenizing Hormone (LH)

Comes from ??

Release stimulated by ??

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  • Also stimulated by high levels of estrogen
  • Inhibited by estrogen & progesterone together
  • Triggers ovulation
  • Maintains the corpus luteum
  • LH surge initiates continuation of meiosis

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Ovulation occurs approximately 10-12 hours after the LH surge and 24-36 hours after peak estradiol levels attained

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Corpus Luteum (“yellow body”)

  • Theca interna & granulosa cells
  • Directed by LH
  • Synthesizes estrogen and significant amounts of progesterone (40 mg/day)
  • Progesterone causes secretory endometrium in preparation for implantation

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Indicators of Ovulation

Prospective or retrospective?

  • Basal body temperature
  • Urinary LH
  • Serum progesterone

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Ovum lives approximately 24 hours after it is released but is fertilizable less than half that time

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Uterine Cycle

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Uterine Cycle

Proliferative Phase

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  • Estrogen dominates
  • Parallels follicular phase of the ovary
  • Growth of blood vessels, mucosa and glands

Secretory Phase

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  • Progesterone dominant
  • Parallels luteal phase
  • Mucous producing

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Normal Menstruation

  • Predominantly arterial
  • Usual duration 3-5 days
  • 1 to 8 days still normal
  • Average flow 30 mL
  • More than 80 mL abnormal

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Cervical Changes

  • Estrogen - thins
  • Progesterone - thickens
  • Spinnbarkeit

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  • Fern Patterns

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Breast Changes

  • Estrogen - proliferation of ducts
  • Progesterone - growth of lobules & alveoli

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Mastalgia = cyclic breast pain

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Estrogens

  • Estrone (E1)
  • 17β-estradiol (E2)
  • Estriol (E3)

Which organs/cells are responsible for production of estrogen?

Granulosa cells, theca cells, corpus luteum, and the placenta

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Estrogens

  • 17β-estradiol is the major secreted estrogen
  • Estradiol is the most potent
  • Estriol is the least potent
  • 2% of circulating estradiol is free

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Progesterone

  • Secreted in large amounts by the corpus luteum and the placenta
  • 2% free in circulation
  • Important intermediate in steroid biosynthesis pathway
  • Fluctuate widely during cycle

What does progesterone do?

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Testosterone

  • Secreted by ovaries, adrenal cortex (small) and peripheral conversion androstendedione (half)
  • Follow Circadian rhythms

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What time of day is testosterone its highest?