Oestradiol molecule. Computer graphic of a molecule of the female sex hormone oestradiol (chemical formula: C18.H24.O2). The atoms are represented here by spheres, and are colour coded: carbon is yellow, hydrogen is green and oxygen is red. Oestradiol is the most important of the female sex hormones. It helps regulate the maturation of the female sex characteristics during puberty, and maintains fertility up until the menopause. It can also be given during hormone replacement therapy (HRT) to prevent any adverse symptoms, such as poor memory, hot flushes and anxiety in menopausal women.