And estrogen supplementation undoubtedly has benefits for menopausal women. It helps with hot flashes, confers protection from heart disease, and it can slow the progress of osteoporosis. Also, while the power of estrogen is undeniable, its danger lies in its ability to promote growth, including cancerous growth, in body cells. Bone density tests were used to monitor the effects of the therapy. This is not surprising when we realize that the function of estrogen pertains to the osteoclast cells, which dissolve old or imperfect bone, while progesterone mediates the osteoblast cells which build bone.
Osteoporosis occurs when osteoclast activity exceeds osteoblast activity.
Thus, estrogen can slow the loss of bone, but only progesterone can help to build it. Neither age nor time from menopause was an apparent factor. The occurrence of osteoporotic fractures dropped to zero. The cause of this condition has long been a mystery, but it is now believed that a high proportion of PMS sufferers have too much estrogen in their bodies in relation to progesterone. David Steinman discusses the case of a 40-year old woman whose doctor prescribed Provera for her unpredictable menstrual cycle, which included irritability and wild mood swings.