Estrogen is a group of hormones that play a crucial role in the development and regulation of the female reproductive system and secondary sexual characteristics. It is primarily produced in the ovaries, but also in smaller amounts by the adrenal glands and fat tissues. Estrogen is essential for processes such as the menstrual cycle, pregnancy, and the maintenance of bone density. In addition to its reproductive functions, estrogen also affects other systems in the body, including the cardiovascular and skeletal systems. It helps regulate cholesterol levels and supports healthy blood vessel function. Changes in estrogen levels can impact mood, energy levels, and overall health, particularly during events like puberty, menstruation, pregnancy, and menopause.