The Overlooked Female Hormone
By Melissa L. Block, M.Ed.
If ovulation does not occur, no progesterone is made. Anovulatory cycles are not easily detected, since menstruation still happens on schedule as long as estrogen does its part. The resulting imbalance of estrogen (which reaches its highest levels at around the 12th day of the menstrual cycle, with the first day falling on the first day of menstruation) and progesterone leads to a condition of estrogen dominance. When this cycle repeats itself frequently, and when it is amplified by environmental estrogens and those made in excess body fat, the body is in a near-constant state of estrogen overload. Estrogen-sensitive tissues get the message to grow and proliferate, and the symptoms listed in the sidebar on page 73 are the end result. By adding progesterone back into each cycle, and gently augmenting progesterone production during ovulatory cycles, balance can be reestablished.
Women who are in or past menopause can also benefit from natural progesterone supplementation. Natural progesterone stimulates the formation of new bone and may help to prevent breast cancer. It counteracts the blood clotting effects of estrogens, improves vascular tone (the ability of blood vessels to stretch and contract in response to the body's requirements), and is believed to protect against the buildup of atherosclerotic plaques and coronary artery spasms that lead to heart attack.5-7 It's a gentle mood enhancer and helps to maintain normal libido.
Low thyroid activity is a common problem for postmenopausal women. Estrogen inhibits thyroid hormone activity.19 Balancing excess estrogens with progesterone enables the body to better utilize thyroid hormone, and can help women to wean themselves off of thyroid hormone replacement drugs.
Progesterone builds bones
One of the main arguments in favor of HRT is that it has been shown in multiple studies to preserve bone mass and protect against osteoporotic fractures. The truth is that while estrogens - even the horse-derived estrogens that comprise Premarin - do preserve bone mass, the overall risks of HRT have been found to outweigh any beneficial effects it might have on bone health.
The synthetic progestin medroxyprogesterone has been found to increase bone density when given to young women who are not menstruating or ovulating.20 The work of John Lee, M.D., and other like-minded clinicians has shown that natural progesterone has the same bone-building effect in both pre- and postmenopausal women, without the side effects that often occur with the synthetic progestins.
Estrogen maintains bone mass by subduing the activity of osteoclasts - specialized bone cells that break down old bone to make room for new. Progesterone builds bone by stimulating the activity of osteoblasts, bone cells that pull calcium, magnesium and phosphorus from the blood so that it can be incorporated into the bones.
Progesterone and breast cancer
Progesterone modulates much more than the course of a pregnancy. It interacts with estrogen in dozens of ways; the best detailed explanation of these effects can be found in Dr. Lee's writings. The short story on progesterone's relationship with cancer is that while estrogen encourages cellular growth (which is why it is carcinogenic in excess), progesterone encourages cells to differentiate, or mature. Immature cells are more likely to turn into cancerous cells.
Progesterone also encourages cells to undergo apoptosis - programmed cell death. A cell that becomes cancerous avoids apoptosis; it can continue to divide and survive as long as it has fuel and a place to grow. The mechanisms by which estrogen encourages cell growth are also thought to help switch off the genetic machinery that brings on programmed cell death.9-12
Progesterone also reduces the production of a carcinogenic form of estrogen (4-hydroxyestrone) and enhances the production of estriol, a safer, non-carcinogenic estrogen. Breast cancer surgery or biopsy performed during the luteal phase of the menstrual cycle - the phase during which progesterone levels peak - is associated with significant improvements in prognosis and survival time.21-23 Progesterone counteracts estrogen's effects on breast duct cells, which are usually the place where breast tumors begin to form.
Estrogen encourages breast duct cell proliferation; progesterone encourages those cells to mature and differentiate. This is how estrogen and progesterone interact during pregnancy to ready the breasts for lactation. Mature, differentiated cells are far less vulnerable to cancerous changes, a fact that explains why women who have had full-term pregnancies are at less risk of developing breast cancer.
Natural progesterone cream is increasingly being used in lieu of synthetic progestin drugs. Like any hormone - natural or synthetic - it's bound to have more significant effects in some people than in others, because of subtle biochemical differences. Fortunately, there is no risk involved in trying it as long as it is used properly. Natural progesterone is now available in an enhanced delivery skin cream (QuSome® encapsulated) to better maintain a consistent youthful level of progesterone in the body.
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