This profile evaluates the important oestrogen metabolites (2/4/16a-hydroxyestrones) as well as their methylated by products, which provides valuable information about oestrogen-related diseases, such as breast cancer, prostate disease risk, osteoporosis and certain autoimmune conditions. Oestrogen methylation is a critical step in the protective mechanism of oestrogen metabolism: methylation is required for the protective effects of 2-hydroxy-estrone, and for the safe detoxification of 4-hydroxy-estrone.