Q. I'm thinking about trying a natural progesterone cream because of all the advertised benefits -- help with fatigue, PMS, weight, and a boost for my immune system. Will the cream work, or is it a placebo?

A. It depends on which supplement you choose. Natural progesterone is made from wild yams; however, it must be altered biochemically to be absorbed. That is because the active ingredient of wild yam -- a substance known as dioscorea -- doesn't bind to the progesterone receptors in your body. In other words, your body can't use it in its natural state.

In women who have an intact uterus, postmenopausal estrogen taken alone can cause a cancerous overgrowth of the uterine lining unless progesterone is also taken. Most progesterone creams aren't absorbed well enough to prevent this overgrowth.

If you use progesterone cream, choose a brand that says "progesterone USP" on the label. Women who use progesterone-supplemented creams should have their progesterone levels measured, either by saliva testing or blood. In addition, make sure your health-care provider knows you are using the cream; natural progesterone could be dangerous if used along with estrogen in hormone replacement therapy.