Hormones: puberty, the menstrual cycle and the menopause

Hormones are chemicals that are made and secreted by groups of specialised cells called glands. Hormones are transported around the body in the blood plasma, and detected by receptors on cells and tissues. During puberty, hormones cause maturation of the sex organs and development of secondary sexual characteristics. Hormones control the menstrual cycle in adult human females, by causing ovulation and menstruation. Decreases in hormone levels in older human females cause the menopause, after which the menstrual cycle stops.