Estrogens

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Summary

Estradiol and Diethylstilbestrol (DES) are estrogens used as drugs to mimic the hormone estrogen’s effects on the body. They bind to estrogen receptors and can be used for contraception (found in oral contraceptive pills) and hormone replacement therapy.  Ethinyl estradiol is the major estrogen used in clinical practice, especially since DES has been found to be associated with an increased risk of vaginal clear cell adenocarcinoma.  Increased risk of endometrial cancer and clotting as deep venous thrombosis (DVT) or pulmonary embolism (PE) are the major adverse effects of pharmacologic estrogen.

Key Points

  • Estrogens
    • Medications
      • Ethinyl estradiol
      • Diethylstilbestrol (DES)
      • Mestranol
    • Mechanism
      • Binds estrogen receptors
        • Increases proliferation of endometrium
        • Increases ovarian follicle growth
        • Increases endometrial excitability
    • Indications
      • Hormone Replacement Therapy
        • Replaces estrogen to relieve menopausal symptoms
          • E.g. vaginal atrophy/irritation and osteoporosis
      • Contraception
        • Combined with progestins to make common oral contraceptive pills (OCPs)
        • May also be used to treat irregular menses
      • Hypogonadism
        • Estrogen stimulates the development of female gonads (ovaries)
    • Adverse Effects
      • Endometrial cancer 
        • Estrogen given without progesterone increases endometrial growth and risk of endometrial cancer.
        • Combination with progesterone reduces this risk (as is done in most OCPs)
      • DVT/PE (clot risk)
        • Contraindicated with history of DVT/PE, in smokers, and other hypercoagulable states
      • DES only: Vaginal adenosis/clear cell adenocarcinoma 
        • Seen in female offspring of pregnant women taking DES
        • Replacement of vaginal squamous epithelium with glandular columnar epithelium leads to increased risk of vaginal cancer
      • Bleeding in postmenopausal women
      • Contraindicated in ER-positive breast cancer
        • Estrogen increases tumor growth in estrogen-receptive cancers