Estrogens are a group of hormones that play an important role in normal sexual and reproductive development in women. Estrogens serve many functions in the body. They stimulate oocyte maturation and endometrial growth, decrease bone resorption, initiate the development of secondary sex characteristics, maintain reproductive organs and glands, and affect the activity of the central nervous system. At menopause, the decrease in estrogen concentrations is often accompanied by vascular instability (hot flushes and night sweats), a rise in the incidence of heart disease, and an increasing rate of bone loss. Estrogen is available as an oral drug, a transdermal patch, or as a gel or lotion. Transdermal estrogen is preferable as compared to oral, since it avoids the first-pass metabolism in the liver. Since release of the WHI findings, current treatment recommendations are for the lowest effective dose for the shortest period of time to treat postmenopausal symptoms.