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  • Contraception
    • How can we disrupt normal HPG axis?
      • prevent follicle development
      • block corpus luteum
      • unreceptive endometrium
      • prevent ovulation
    • Aim
      • prevent pregnancy by either blocking access of sperm to egg or disrupt female reproductive cycle
    • hormonal contraceptives
      • progesterone-only contraceptives
        • Efficacy
          • very low failure rate (< 1%) if taken correctly
        • Depo contraceptive injections (medroxyprogesterone acetate)
          • effect ovaries (follicles)
            • inhibit follicle maturation, inhibit ovulation, inhibit corpus luteum
          • higher dose of progesterone, inhibit GnRG release in hypothalamus inhibit FSH and LH secretion in anterior pituitary
          • effect uterus (endometrium)
            • thicken cervical mucous, modify tubule motility, endometrial changes
        • Mini-pill
        • side effects
          • rare (acne, breast tenderness and breast enlargement, mood changes, headaches, nausea)depo injections - can take up to 2 years to recover normal fertility
      • combined oral contraceptives
        • Hormonal contraception containing estrogen and progestin, which acts by suppressing ovulation, thickening the cervical mucus to block semen, and altering the uterine decidua to prevent implantation
        • oestrogen and progesterone effect on female reproductive axis
          • inhibits GnRH release from hypothalamus and decrease response in anterior pituitary, inhibits FSH and LH secretion from anterior pituitary
        • oestrogen and progesterone effect on ovaries (follicles)
          • Inhibit follicle maturation, inhibit ovulation, inhibit corpus luteum
        • oestrogen and progesterone effect on uterus (endometrium)
          • Thicken cervical mucous, modify tubule motility, endometrial changes (thins)
        • Efficacy
          • Very low failure rate (0.05%) - interferes with multiple steps of ovulation. Usually caused by missed doses, drug interactions (some antibiotics), diarrhoea and vomiting
        • Side effects
          • increased risk of CVD, breast cancer, minor effects include nausea, weight gain, depression
        • Health benefits
          • decreased risk of ovarian and endometrial cancer, decreased incidence of PID and ovarian cysts
      • morning after pill
        • Emergency contraception used within 72 hrs after unprotected sex.High dose Progesterone only.
        • Primary mechanism
          • Inhibit ovulation (will not work if this has already occurred). Suppression of HPG - inhibit FSH and LH.Efficacy rates ~ 75-85%.
      • RU486 (mifepristone): abortive agent(not in UK)
        • Progesterone antagonist
        • MOA
          • depends on stage of cycle:Mid-cycle disrupts ovulation, Luteal phase prevents implantation, after implantation causes loss of foetus
          • Mimics endogenous hormone
    • Male contraceptive pill
      • side effects
        • sexual dysfunction & weight gain
      • MOA
        • stop sperm production
        • inhibit sperm motility
        • inhibit testosterone production
      • example - dimethandrolone undecanoate (DMAU) - androgen receptor agonist.


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