Endocrine Pharmacology TOPIC
23. Physiology Overview: The Reproductive System

I. The Female Reproductive System     top

Figure 23.1 Feedback Control of Ovarian Hormone Production
  1. Feedback Control of Ovarian Hormone Production
  2. The Menstrual Cycle
    Figure 23.2 The Menstral Cycle

    1. Follicular phase
      • The menstrual cycle begins as FSH stimulates development of an ovarian follicle. As this follicle matures, it begins producing a small but steadily rising amount of estradiol. This low level of estradiol causes:
        • Negative feedback: inhibition of FSH and LH secretion
        • Growth of the lining of the uterus
    2. Ovulation
      • The amount of estradiol secreted at mid-cycle has increased to the high level that stimulates a surge of FSH and LH release by the pituitary
      • The LH surge causes ovulation: the follicle ruptures and releases its egg near the opening of its fallopian tube
    3. Luteal Phase
      • Following the release of its egg, the follicle changes into a hormone-secreting structure, the corpus luteum, and secretes estradiol and progesterone in response to LH.
        • Estradiol and progesterone stimulate the continued development of the lining of uterus
      • If pregnancy does not occur, the corpus luteum eventually disintegrates and stops secreting estradiol and progesterone. The uterine lining sheds and menstruation occurs.
      • If pregnancy occurs, the placenta produces hCG (human chorionic gonadotropin) which maintains corpus luteum's secretion of progesterone
      • At 3 months gestation, the placenta takes over secretion of progesterone

II. The Male Reproductive System      top

  1. Feedback Control of Testicular Hormone Production

Question: Quick Question Question:
What would happen if a woman begins taking a regular, low dose of estradiol at the start of her menstrual cycle (when her own estradiol production is extremely low)?



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