Estrogen has a rapid action known as nongenomic action. In fact, the definition of nongenomic action does not mean that it is not involve the transcription process. This name originated from the first report of Szege et al., who showed that estrogen rapidly increased cyclic adenosine monophosphate (cAMP) within 15 seconds (Szego and Davis 1967). They suggested that it is too rapid to be accounted for classical genomic action due to estrogen acted through the genomic action requires at least 2 hours after estrogen stimulation However, it is now accepted that the nongenomic can indirectly activate gene transcription via several intracellular signaling pathways (Figure 3–11).