Estrogen and progesterone are always associated with women. But just as women have testosterone (the dominant "male hormone"), men have "women's hormones" -- just in smaller amounts. Estrogen is actually pretty close to testosterone from a chemical perspective. In men, estrogen is made from testosterone by an enzyme called aromatose. It contributes to the regulation of the male reproductive system and also influences male behavior. Estrogen tends to increase in men as they age, while testosterone levels decrease.
An estrogen imbalance in men can cause problems. Sometimes the increase results from obesity, because estrogen is made in fat cells, as well as in other places in the body. Men with conditions such as diabetes, prostate cancer and heart failure have been found to have high or low levels of estrogen -- so maintaining hormonal balance is important. Progesterone in men actually helps to regulate estrogen levels, which is why men found to have an estrogen/testosterone imbalance might be prescribed a progesterone supplement.