Estrogen hormones are female sex hormones found in both women and men (where they are thought to play a role in sperm maturation and male libido), but are produced in much higher levels in women of childbearing age. These steroid hormones are primarily responsible for the growth and development of female sexual characteristics, regulation of the menstrual cycle, and management of the reproductive system. They are also under ongoing neuroscientific investigation for their role in brain function and health, particularly as they relate to aging.
During a woman's lifetime, estrogen levels will often fluctuate, rising during puberty and remaining at healthy levels until her 40s and 50s, or the beginning of menopause. At this point, estrogen production significantly drops, signaling the end of natural fertility and impacting the brain in ways that may be associated with mood changes, anxiety, depression, memory loss, and diminished neuroprotection.