Estrone (E1, and also oestrone) is an estrogenic hormone secreted by the ovary as well as adipose tissue with the chemical name of 3-hydroxyestra-1,3,5(10)-triene-17-one and the chemical formula C18H22O2. Estrone is an odorless, solid crystalline powder, white in color with a melting point of 254.5 °C and a specific gravity of 1.23. Estrone is one of several natural estrogens, which also include estriol and estradiol. Estrone is the least abundant of the three hormones; estradiol is present almost always in the reproductive female body, and estriol is abundant primarily during pregnancy. Estrone is known to be a carcinogen for human females as well as cause breast tenderness or pain, nausea, headache, hypertension, and leg cramps. In men, estrone has been known to cause anorexia, nausea, vomiting, and erectile dysfunction. Estrone is relevant to health and disease states because of its conversion to estrone sulfate, a long-lived derivative. Estrone sulfate acts as a reservoir that can be converted as needed to the more active estradiol. It is the predominant estrogen in postmenopausal women.