2-OH-E1, also known as 2-hydroxyestrone, is a natural metabolite of estrogen in the human body. It is derived from estrone, which is one of the three main types of estrogen produced by the ovaries in females and in smaller amounts by the testes in males.

Estrogens, including 2-OH-E1, play essential roles in regulating various physiological processes in the body, such as the development of secondary sexual characteristics, menstrual cycle regulation, and maintenance of bone density. They also influence the growth and function of reproductive tissues.

The "2-OH" in 2-OH-E1 refers to the presence of a hydroxyl group (OH) on the second carbon of the estrogen molecule. The different forms of estrogen metabolites, including 2-OH-E1, can have varying effects on the body and may be associated with different health outcomes. These metabolites can also serve as biomarkers in medical research and clinical practice to assess estrogen metabolism and its potential implications for health.