This hormone is important in pregnancy, perimenopause and post menopause. This hormone can help with PMS symptoms and sleep disorders. It reduces bloating, headaches, cyclic migraines and fluid retention. This hormone works synergistically with estrogen and the lack of this important hormone will result in osteoporosis, a decrease in libido and an increase in heart disease. Unfortunately, the synthetic hormone can cause side effects such as bloating, breast tenderness, bleeding and low mood, whereas the natural, bio-identical form does not.