Esterified estrogen is a plant-based product made from yams and soy. Its big claim to fame: You can take a much lower dosage than other forms of estrogen, but still get the same benefits in terms of eliminating symptoms, preventing osteoporosis and helping to fight heart disease.

According to studies, esterified estrogen prevents osteoporosis at half the dose of conjugated estrogens (Premarin) -- and apparently has fewer side effects. One study conducted by researchers at the University of California-San Francisco scientist found that esterified estrogen didn’t cause the increase in vaginal bleeding or build-up of the uterine walls -- which is the precursor to endometrial cancer -- that conjugated estrogens do. In fact, some researchers believe that you may not need to take a progestin or progesterone with this form of estrogen (since usually these are prescribed to fight against the possibility of endometrial cancer) or may be able to take a lower dose.

This looks promising because many women who report side effects from HRT have these from taking a progestin. However, more studies will be done to determine whether this theory is correct. In addition, probably because you get positive effects from a lower dose than that of Premarin or micronized estradiol, esterified estrogen doesn’t seem to cause as great an increase in breast tenderness, headaches or nausea as Premarin.

One important note:  one form of esterified estrogen, Estratab, has been unavailable since spring 2001.  Some sources say it will be reintroduced in the future, but it's unclear when this will happen.  Keep in touch with your doctor or pharmacy, or contact the pharmaceutical company for more information.

• Standard dosage: .3, .625, 1.25, and 2.5 mg
• Pros: Natural; low dosage appears to prevent osteoporosis and heart disease as well as minimize menopausal symptoms, but with fewer side effects than other higher dose forms of estrogen
• Cons: Often difficult to get in the U.S.