oestrogen

one of a group of STEROID hormones secreted mainly by the ovaries and, to a lesser extent, by the adrenal cortex and PLACENTA . (The TESTICLES also produce small amounts.) Oestrogens control the female SECONDARY SEXUAL CHARACTERISTICS , i.e. enlargement of the breasts, change in the profile of the PELVIC GIRDLE , public hair growth and deposition of body fat. High levels are produced at ovulation and, with PROGESTERONE , they regulate the female reproductive cycle. Naturally occurring oestrogens include OESTRADIOL , oestriol and oestrone. Synthetic varieties are used in the contraceptive pill and to treat gynaecological disorders.