II. Physiology: Follicular Phase (Proliferative phase in Early Cycle)

  1. Follicle Stimulating Hormone (FSH) stimulates ovary
    1. Dominant ovarian follicle emerges days 5-7 of cycle
    2. Vascularity doubles for dominant follicle
    3. Twin Gestation prone generate 2 dominant follicles
    4. Ovarian follicle produces Estrogen
  2. Endometrium proliferative of glands and stroma
  3. Mean Duration: 10.8 days
  4. Hormones low
    1. Follicle Stimulating Hormone (FSH) low but rising
    2. Luteinizing hormone (LH) low but rising
    3. Progesterone remains low

III. Physiology: Ovulatory Phase (Mid-Cycle)

  1. Hormone Surge
    1. Estrogen rapidly peaks Days 10-15, then decreases
    2. Follicle Stimulating Hormone (FSH) with small surge
      1. Stimulates Ovulation
      2. Results in start of Progesterone increase
    3. Luteinizing hormone (LH) large surge
  2. Mid-cycle Symptoms Include
    1. Spotting
    2. Increased vaginal secretions
    3. Increased libido
    4. Nausea
    5. Abdominal Pain (Mittelschmerz)

IV. Physiology: Luteal Phase (Secretory phase in Late Cycle)

  1. Endometrium secretive
  2. Mean Duration: 13.3 days
  3. Hormonal changes
    1. Estrogen continues to be high days 16-24
    2. Progesterone surges and remains until days 16-24
      1. Progesterone depletes Estrogen receptors
      2. Progesterone level falls to 0 at end of cycle
      3. Bleeding from Progesterone withdrawal occurs
    3. Luteinizing hormone (LH) returns to normal
    4. Follicle Stimulating Hormone (FSH) returns to normal

V. Physiology: Menstrual Phase (Bleeding)

  1. Demise of corpus luteum
  2. Estrogen and Progesterone withdrawal
  3. Sloughing of endometrium
  4. Normal Menstrual Bleeding per cycle
    1. Duration: 2-8 days (mean: 4 days)
    2. Blood Loss: 20-80 ml (mean 35 ml), 13 mg iron loss
    3. Intervals: 21-35 days (mean 28 days)

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