Estrogen is a hormone primarily produced by the ovaries, with smaller amounts being produced by the placenta and male testes. It plays a crucial role in regulating sexual development, including the changes that occur during puberty. Additionally, estrogen influences the menstrual cycle, lactation following pregnancy, mood variations, and the aging process. Throughout a woman's life, estrogen levels naturally fluctuate, peaking at puberty and gradually decreasing during middle age until menopause. A deficiency in estrogen can result in limited sexual development, ongoing menopausal symptoms like mood swings and vaginal dryness, and health issues in older age. To address estrogen deficiency, natural or synthetic estrogen treatments may be prescribed. Estrogen is also a key ingredient in many birth control pills. In men, excessive estrogen can lead to the development of female characteristics, such as breast tissue enlargement.