The hormone progesterone plays an important role in the health of all women. This sex steroid affects reproduction, cognition and emotions across the entire lifespan. Released mainly from the ovaries, natural progesterone quickly circulates throughout the body and readily enters the central nervous system. Older females, especially postmenopausal women, often experience a dramatic decrease in hormone production. Such women may elect to take bioidentical progesterone as a part of replacement therapy. Yet, replacement can cause unwanted side effects.
Breast Density Changes
Micronized progesterone, a natural form of the hormone, is typically administered either orally or vaginally. This type of replacement therapy may cause changes in the female breast. A report by G.A. Greendale and co-workers presented in the Jan. 1, 2003, edition of the medical journal "JNCI," the Journal of the National Cancer Institute showed that one year's use of synthetic estrogen and bioidentical progesterone increased breast density 3 to 5 percent. Estrogen alone did not alter breast density, implicating progesterone as the causal factor. While not necessarily cancerous, such changes are considered an early warning sign of breast cancer.
Luteinizing Hormone Suppression
Premenopausal women often take birth control pills to prevent pregnancy. These pills contain synthetic forms of estrogen and progesterone, both of which suppress ovulation. Such effects are achieved by reducing circulating levels of luteinizing hormone, LH. Natural progesterone may have a similar effect. A study by S. Livadas and associates looked at the effects of micronized progesterone on LH secretion in younger females with polycystic ovary syndrome, PCOS. These women have low levels of progesterone and fail to ovulate. Data from the Livadas study, published in the June 2010 edition of "Fertility and Sterility," showed that micronized progesterone enhanced circulating progesterone. It also, however, suppressed LH and thus fostered the symptoms of PCOS.
Testosterone Suppression
Sex steroids testosterone, progesterone and estrogen derive from the cholesterol molecule. Altering one of these three hormones typically affects the other two. A report by T. Bagis and colleagues offered in the October 2002 issue of "Journal of Clinical Endocrinology & Metabolism" evaluated the relationship between progesterone and testosterone in PCOS women. Results indicated that enhancing progesterone decreased testosterone. Such results raise concerns because testosterone plays an important role in tissue growth. Progesterone-induced testosterone suppression could, therefore, lead to wasting and injury.
Fetal Impact
Progesterone increases during pregnancy to help protect the fetus. Doctors, therefore, may prescribe natural hormones for women at risk for premature birth. According to H. How and B. M. Sibai, such supplementation may have adverse effects on the unborn child. Their review, published in the February 2009 issue of "Therapeutics and Clinical Risk Management," suggested that progesterone exposure changes fetal arousal patterns. This claim was based on animal research showing the hormone reduced the time unborn pups spend awake. The implication of these results remains unknown, and comparable studies in humans remain undone. Still, pregnant women should carefully consider the risks of taking natural progesterone.
References
- "JNCI": Postmenopausal Hormone Therapy and Change in Mammographic Density
- "Fertility and Sterility"; Effect of Oral Micronized Progesterone on Hormonal and Metabolic Parameters in Anovulatory Patients with Polycystic Ovary Syndrome; S. Livadas et al.; June 2010
- "Journal of Clinical Endocrinology & Metabolism": Effects of Short-Term Medroxyprogesterone Acetate and Micronized Progesterone on Glucose Metabolism and Lipid Profiles in Patients with Polycystic Ovary Syndrome: A Prospective Randomized Study
- "Therapeutics and Clinical Risk Management": Progesterone for the Prevention of Preterm Birth: Indications, When to Initiate, Efficacy and Safety
