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Oestrogen and Progesterone: Mechanisms, Therapeutic Uses, Derivatives, Adverse Effects, and Contraindications
Oestrogen
Mechanism of Action
- Oestrogen binds to oestrogen receptors (ER) in target tissues like the reproductive system, bones, and cardiovascular system.
- It activates gene transcription and protein synthesis, maintaining female secondary sexual characteristics and reproductive function.
Therapeutic Uses
- Contraception (combined with progestins in oral contraceptives).
- Hormone Replacement Therapy (HRT) for menopausal symptoms and osteoporosis prevention.
- Primary Hypogonadism treatment to induce puberty in individuals with underdeveloped ovaries.
- Endometriosis and Dysmenorrhea treatment for regulating menstrual cycles and pain reduction.
Adverse Effects
- Cardiovascular risks such as thromboembolism, stroke, and myocardial infarction.
- Increased risk of breast cancer with long-term use.
- Endometrial cancer risk, especially when used alone without a progestin.
- Headaches and migraines in susceptible individuals.
Contraindications
- Breast cancer (active or history of).
- Venous thromboembolism (DVT or pulmonary embolism history).
- Liver disease (severe dysfunction).
- Undiagnosed vaginal bleeding.
Oestrogen Derivatives
- Ethinylestradiol: A synthetic derivative used in oral contraceptives and hormone replacement therapy (HRT).
- Estradiol (E2): The most potent form of oestrogen, used in HRT.
- Conjugated Oestrogens (Premarin): A mixture derived from pregnant mare urine, used in HRT.
- Diethylstilbestrol (DES): A synthetic nonsteroidal oestrogen used in the past for HRT but now avoided due to serious side effects.
Progesterone
Mechanism of Action
- Progesterone binds to progesterone receptors (PR) in the uterus and breasts, regulating the menstrual cycle and preparing the uterus for implantation.
- It inhibits ovulation by suppressing gonadotropins (LH and FSH) from the anterior pituitary.
Therapeutic Uses
- Contraception (progestins used in pills, implants, and IUDs).
- Hormone Replacement Therapy (HRT) for endometrial protection in postmenopausal women.
- Prevention of preterm labor in women with a history of premature birth.
- Treatment of endometrial cancer, particularly in advanced cases.
Adverse Effects
- Weight gain due to fluid retention and increased appetite.
- Mood changes such as depression, anxiety, and irritability.
- Breakthrough bleeding, especially with contraceptive use.
- Breast tenderness and increased sensitivity.
Contraindications
- Active liver disease.
- Undiagnosed vaginal bleeding.
- History of breast cancer.
- Thromboembolic disorders (history of DVT or pulmonary embolism).
Progesterone Derivatives
- Medroxyprogesterone Acetate (MPA): A synthetic progestin used in contraceptives, HRT, and treatment of endometrial cancer.
- Levonorgestrel: A synthetic progestin commonly used in contraceptive pills, IUDs, and emergency contraception.
- Norethindrone: A synthetic progestin used in birth control pills and hormone therapy.
- Desogestrel: A synthetic progestin often used in combined oral contraceptives.
- Dydrogesterone: A synthetic progestogen used for hormone replacement therapy and menstrual irregularities.
