Endocrine Control Female Reproduction 4 Flashcards

Explain the production of sex hormones.

1
Q

What is the role sex hormone binding globulin (SHBG) in female reproduction?

A
  • High affinity binding protein for estrogens and adrogens
    • androgens bind with higher affinity than estrogens
    • bound hormones considered biologically inactive
    • hormones that are free or loosely associated with albumin are biologically available
  • Hepatic SHBG production increased by the following:
    • estrogen
    • thyroid hormone
  • Production is decreased by the following:
    • androgens
    • obesity
    • insulin
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2
Q

List the major peptides involved in female reproduction?

A
  • Inhibin A and B
  • Activin
  • Follistatin
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3
Q

What is the role of Inhibin A and B in female reproduction?

A
  • Inhibits FSH release
  • Inhibin A
    • present in both granulosa and theca cells
    • secreted by the dominant follicle
    • secreted by the corpus luteum
  • Inhibin B
    • secreted by granulosa cells of small antral follicles
    • increases in response to FSH stimulation
    • feeds back to modulate FSH release
    • marker of gonadal reserve
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4
Q

What is the role of activin in female reproduction?

A
  • homodimer of inhibin beta-subunits
  • synthesized by the pituitary and ovary
  • stimulates FSH release by local autocrine/paracrine rather than endocrine actions
  • most circulating actiin is likely bound to follistatin
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5
Q

What is the role of follistatin in female reproduction?

A
  • inhibits FSH release by binding and neutralizing activin
  • acts locally to inhibit follicular growth
  • autocrine/paracrine actions
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6
Q

Discuss the following stages of female development: menarche, adrenarche, and adult female.

A
  • Menarche
    • median age 12.6 in US
    • occurs about 2 years after breast budding
    • secular trend in age of menarche
    • occurs at earlier ages over the centuries
  • Adrenarche
    • occurs between 6-8 years, prior to onset of puberty
    • development of adrenal zona reticularis - androgen secreting compartment of adrenals
    • results in secretion of adrenal androgen, DHEAS
    • leads to development of pubic and axillary hair
    • uncouple from gonadarche
  • Adult female
    • menstrual cycle 21-35 days in length
    • cycle varies by no more than +/- 2 days
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7
Q

List the phases of the menstrual cycle.

A
  • Ovarian follicular development
  • Follicular phase
    • early
    • mid
    • late
  • Luteal phase
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8
Q

Describe the events during ovarian follicular development.

A
  • Gonadotropin-independent and regulated by intraovarian growth factors
  • Maturation of antral follicles and ovulation with resumption of meiosis requires FSH and LH
  • A single dominant follicle emerges from growing follicle pool 5-7 days after to start of menses
  • Other growing follicles become atretic
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9
Q

Describe the events during the follicular phase.

A
  • Early follicular phase
    • FSH increase persists from of last cycle
    • dominant follicle is selected
    • LH pulse frequency begins to increase in absence of negative feedback of effects of E2 and progesterone
    • LH stimulates thecal cell T production, aromatized into E2 by adjacent granulosa cells of follicle
      • aromatase activity increases with FSH-stimulated follicular growth
      • Inhibin B increases follicular growth
  • Mid follicular phase
    • increasing GnRH pulse frequency
    • synergizes with increasing ovarian E2 and inhibin B production
    • suppresses FSH release
  • Late follicular phase
    • continued increase E2 production induces mid-cycle LH surge
    • induces ovulation of the dominant follicle
    • increased GnRH pulse frequency to ~1 pulse/hour
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10
Q

Describe the events of the luteal phase.

A
  • Period after ovulation, usually 14 days
  • Post ovulatory follicle
    • lueinizes, forming corpus luteum
    • secretes progesterone and E2
    • feed back to slow GnRH pulse frequency
    • as frequency slows, FSH release selectively increases and LH decreases
      • stimulates follicular recruitment to the next cycle
      • progesterone production falls in the face of decreasing LH levels
      • without conception and hCG production, the embryo does not sustain the corpus luteum preogesterone production
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11
Q

Describe the events that occur in the endometrium during the menstrual cycle.

A
  • Proliferation
    • E2 or synthetic estrogens stimulate proliferation od endometrial, stromal, and epithelial cells
    • estrogens also induce expression of progesterone receptors
      • Ability of endometrium to respond to progesterone depends on estrogen induction of progesterone receptors
  • Differentiation
    • Prgestins such as progesterone or synthetic progestins induce differentiation of the poliferative endometrium
    • P also prepares the endometrium for implantation of the embryo
  • Menstruation
    • In the absence of hCH produced by the embryo, P and E2 production by the corpus luteum stops
    • this withdrawal of P and E2 leads to vasomotor changes in the endometrium and shedding of the endometrial lining
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12
Q

Describe the events that occur during menopause.

A
  • cessation of ovarian follicular activity
  • mean age 51-52 years
  • ovarian estradiol virtually ceases at menopause
  • ovarian androgen production continues from some years afterwards
  • Androgens, primarily androstenedione can be aromatized extragonadally into estrogen
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