Estrogen has been one of the most studied hormones in the scientific arena. A search of PubMed using the keyword “estrogen” reveals over 113,000 citations/publications since 1934, with more than 40% of the published papers appearing in the last 10 years. Thus, the area of estrogen research has seen a relative explosion in the last decade. Much of the interest has been sparked by a desire to understand the actions and mechanisms of estrogen throughout the body,
and to formulate better diagnoses and treatment for breast cancer, osteoporosis, cardiovascular and neurological disease and a multitude of postmenopausal symptoms. Classically, estrogen is considered a “reproductive” hormone, due to its well-known role in feedback signaling in the hypothalamicpituitary-ovarian axis. The reproductive actions and roles of estrogen have been reviewed extensively previously, and the reader is referred to several excellent reviews on this subject [1–5].