<unk>  <unk> , also spelled<unk> , is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous and menstrual female reproductive cycles.<unk>  is responsible for the development of female secondary sexual characteristics such as the breasts, widening of the hips and a female-associated pattern of fat distribution. It is also important in the development and maintenance of female reproductive tissues such as the mammary glands, uterus and vagina during puberty, adulthood and pregnancy. It also has important effects in many other tissues including bone, fat, skin, liver, and the brain. Though<unk>  levels in males are much lower than in females,<unk>  has important roles in males as well. Apart from humans and other mammals,<unk>  is also found in most vertebrates and crustaceans, insects, fish, and other animal species.<unk>  is produced especially within the follicles of the ovaries, but also in other tissues including the testicles, the adrenal glands, fat, liver, the breasts, and the brain.<unk>  is produced in the body from cholesterol through a series of reactions and intermediates. The major pathway involves the formation of androstenedione, which is then converted by aromatase into estrone and is subsequently converted into<unk> . Alternatively, androstenedione can be converted into testosterone, which can then be converted into<unk> . Upon menopause in females, production of estrogens by the ovaries stops and<unk>  levels decrease to very low levels. In addition to its role as a natural hormone,<unk>  is used as a medication, for instance in menopausal hormone therapy and feminizing hormone therapy for transgender women; for information on<unk>  as a medication, see the<unk>  (medication) article.
Estradiol
Estrogen
Estrogen 
Alfatradiol
Androgen
Progesterone 
Progesterone
Methyltestosterone