As an example, both natural progesterone and the synthetic counterparts, which are called progestins, help prevent cancer like uterine cancer. However, only natural progesterone protects against breast cancer, normalizes the fatty acid profile, restores normal sex drive, and regulates sleep patterns.

Progestins, on the other hand, contribute to mood swings, fatigue, depression, insomnia, bloating, breast tenderness, weight gain, and anxiety ' of which none are side effects of natural progesterone.

Synthetic estrogens are altered so that drug companies make them individual and patent them. They tend to be stronger and more toxic than estrogens manufactured naturally in the human body; and so they increase the odds of having symptoms of estrogen dominance, which are weight gain, bloating, anxiety, depression, and low blood sugar, and from estrogen-related diseases like breast and uterine cancer. The natural forms of estrogen, i.e. estradiol, estrone, and estriol, tend to be safer.

It's important to note that most studies of hormone replacement therapy involve the use of synthetic hormones. Don't assume that all hormone replacement therapy brings about the same results we've seen in the recent studies, all of which used synthetic hormones. We're in need of some valid long-term studies on the effects of the natural and synthetic versions of both progesterone and estrogen.

Estrogen and progesterone work as opposites to maintain hormonal balance. But they also help sensitize receptors for each other throughout the body. That is, progesterone helps the body take up and use estrogen, and estrogen helps the body take up and use progesterone. Estrogen is responsible for the creation of the soft female form.

It promotes cell growth, which is why it can be dangerous in the presence of certain estrogen-dependent cancers, like those of the breast, ovaries or uterine lining. It's also responsible for increased body fat, retention of sale and fluid, and a decrease in the sex drive. All of this makes sense when the body is being prepared for motherhood.

Progesterone, on the other hand, helps keep estrogen in line. While estrogen promotes the buildup of the uterine lining, progesterone triggers the breakdown and shedding of that lining. Estrogen is almost never prescribed without progesterone for a woman who has an intact uterus, because estrogen will cause overgrowth of the uterine lining, which can lead to cancer. While estrogen may increase body fat, progesterone helps the body use that fat for energy. Estrogen impairs the sex drive; progesterone restores it. Estrogen increases blood clotting; progesterone normalizes it and, together, these two hormones keep the female reproductive system, and may other bodily functions, working together.

During perimenopause, when ovulation becomes sporadic, there will be some months when there's no substance produced to manufacture progesterone. During these months, your progesterone levels are close to zero ' as low as those found in postmenopausal women. Yet estrogen production will continue as if nothing has happened. This creates a phenomenon called estrogen dominance, in which estrogen is allowed to run unchecked without the normal balancing effect of progesterone.

The result is an unhappy long list of symptoms familiar to many women experiencing perimenopause, which include weight gain, bloating, breast tenderness, low blood sugar, fatigue, lack of sex drive, migraine headaches, irritability, and emotional hypersensitivity. These are all common indications of too much estrogen and not enough progesterone. If this sounds like PMS, that's because PMS is often due to estrogen dominance as well.