Gynecology Book


Menstrual Cycle

Aka: Menstrual Cycle, Follicular Phase, Ovulatory Phase, Luteal Phase
  1. See Also
    1. Cervical Mucus
    2. Basal Body Temperature
  2. 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
  3. 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)
  4. 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
  5. 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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