Conventional hormone replacement therapy became highly controversial following the Women's Health Initiative Study, which was halted, according to the April 2004 "Journal of the American Medical Association," when it was determined that the health risks to the women participating in the study were too great. Bioidentical hormone therapy has risen in popularity as an alternative that poses fewer risks. Controversy continues regarding the relative safety and effectiveness of both methods.
Menopausal Symptoms
Women in four different studies who were switched from conventional to bioidentical hormone replacement reported fewer side effects and significant improvement in menopausal symptoms, according to a study published in the January 2009 journal "Postgraduate Medicine." Bioidentical progesterone compared with synthetic progesterone resulted in a 30 percent reduction in sleep problems, a 50 percent reduction in anxiety, a 60 percent reduction in depression, a 30 percent reduction in somatic symptoms, a 25 percent reduction in menstrual bleeding, a 40 percent reduction in cognitive difficulties and a 30 percent improvement in sexual function.
Physiological Effects
Regardless of the way studies have been designed or carried out, considerable differences have been found between the effects of synthetic progestins versus bioidentical progesterones, particularly on breast tissue, according to "Postgraduate Medicine." Apoptosis--a measure of the programmed rate of cell death--is inhibited by progestins but increased by progesterone. Additionally, progesterone inhibits breast cell division, makes breast cells less sensitive to estrogen and increases apoptosis of breast cancer cells. Synthetic progestins increase breast cell proliferation and increases estrogenic effects on breast cells. This stark contrast in physiological effects between the two forms of hormone replacement therapy has implications for their long-term health effects.
Progesterone and Breast Cancer Risk
The Women's Health Initiative, a 15-year multi-million dollar study on the causes of disease and death in postmenopausal women, found that breast cancer risk increased significantly with the use of synthetic progestins. Another large study, known as the Nurses' Health Study, found a 67 percent increased risk for breast cancer when synthetic progestins were used in combination with estrogen, compared to no hormone replacement. Risk increased by 7.6 percent per year of synthetic hormone use.
Estrogen and Breast Cancer Risk
There are three primary forms of estrogen and two kinds of estrogen receptors that are important in relation to breast cancer risk. Estriol activates a receptor that inhibits breast cell proliferation, estrone activates a receptor that increases breast cell proliferation and estradiol activates both receptors equally. Synthetic progestins and equine-derived estrogens inhibit the receptors that inhibit cell proliferation, thereby encouraging rapid cell division and increasing risk for breast cancer, according to a study published in the February 2003 "Reproductive Biology and Endocrinology."
Progesterone and Cardiovascular Risk
The Women's Health Initiative study found a substantial increase in risk of heart attack and stroke for women taking progestins together with equine estrogen. Expressed in terms of excess risks per 10,000 person-years, the study predicted seven more coronary heart disease events, eight more strokes and eight more invasive breast cancers, according to an article published in the July 2002 "Journal of the American Medical Association." Synthetic progestins counteract the protective effect of estrogen on blood lipids and also directly lower HDL levels. Progesterone supports and enhances estrogen's cardio-protective effects, according to "Postgraduate Medicine."
References
- Holtorf Medical Group: The Bioidentical Hormone Debate: Are Bioidentical Hormones (Estradiol, Estriol and Progesterone) Safer or More Efficacious than Commonly Used Synthetic Versions in Hormone Replacement Therapy?
- National Institutes of Health: Postmenopausal Hormone Therapy
- National Institutes of Health: Effect of Long-Term Treatment with Steroid Hormones or Tamoxifen on the Progesterone Receptor and Androgen Receptor in the Endometrium of Ovariectomized Cynomolgus Macaques
- "Journal of the American Medical Association": Effects of Conjugated Equine Estrogen in Postmenopausal Women With Hysterectomy
- "Journal of the American Medical Association": Risks and Benefits of Estrogen Plus Progestin in Healthy Postmenopausal Women
