Pharmacology of Estrogens

Estrogens for hormone therapy may be separated by chemical composition or by route of administration. Natural estrogens include estradiol, estrone, estriol, and their conjugates as well as conjugated equine estrogens (CEEs). Synthetic estrogens include ethinyl estradiol, mestranol, quinestrol, diethylstilbestrol, and raloxifene. Parenteral routes of administration include injection, transvaginal, transdermal patches, subcutaneous pellets, intranasal, and percutaneous gel administration. No matter the type of estrogen or the route of administration, large intraindividual and interindividual variations of serum concentrations occur. Estrogen replacement is beneficial for symptomatic relief of hot flushes and genitourinary symptoms and for prevention of osteoporosis. The lowest dosage that relieves symptoms and is effective in preventing osteoporosis should be used. There is limited information on the interaction of diseases and drugs with estrogen in postmenopausal women receiving replacement therapy.