Hormones are chemical messengers responsible for various functions in the body. Female sex hormones not only play a vital role in sexual development, fertility, and general health, but can also affect appetite, sleep, hair and bone loss, and sexual desire or libido. Hormone levels can change dramatically over time, especially during puberty, pregnancy, and menopause. A hormone test can help identify and monitor these changes. Other factors that can affect female sex hormones include menstruation, stress, medications, and environmental influences.