Estrogens are female sex hormones essential for reproductive tissue development, breast growth, and bone health.
Physiological Sources:
Produced primarily by the ovaries (granulosa cells) and the placenta during pregnancy.
Types of Estrogens:
Endogenous: Estradiol (most potent), estrone, estriol.
Exogenous (Synthetic): Ethinylestradiol, conjugated estrogens.
Pharmacological Actions:
Female Sexual Development: Growth and maturation of reproductive organs and secondary sexual characteristics.
Bone Metabolism: Inhibit bone resorption, protecting against osteoporosis.
Lipid Metabolism: Increase HDL and decrease LDL (cardioprotective).
Blood Coagulation: Increase clotting factor synthesis (risk of thromboembolism with high doses).
Pharmacological Agents:
Estradiol: Most potent natural estrogen, used in HRT and contraceptives.
Ethinylestradiol: Synthetic estrogen in combined oral contraceptives.
Conjugated Estrogens (e.g., Premarin): Used in HRT.
Mechanism of Action:
Estrogens bind to estrogen receptors in target tissues, regulating gene expression to support secondary sexual characteristics, menstrual cycle regulation, and bone density maintenance.
Clinical Uses:
Hormone Replacement Therapy (HRT): Relieve menopausal symptoms, prevent osteoporosis.
Contraception: Combined with progestins.
Menstrual Disorders: Treat amenorrhea and dysmenorrhea.
Cancer Management: Breast and prostate cancer treatment.
Side Effects:
Common: Nausea, breast tenderness, weight gain, mood changes.
Serious: Increased risk of thromboembolism, stroke, breast cancer, endometrial cancer (if unopposed by progesterone), and liver dysfunction.