The female sex hormone is composed of two hormones, OESTROGEN and ESTROGEN. OESTROGEN is a nine-letter word and is the primary female sex hormone, responsible for the development of female secondary sexual characteristics such as breasts and hips. ESTROGEN is an eight-letter word and is a weaker form of OESTROGEN, but still plays an important role in female reproductive health. Both hormones are produced by the ovaries and are essential for the regulation of the menstrual cycle.