Written by JANE ALLIN
Research Analyst | Int’l Fund for Horses
Despite the tainted history of Premarin® and its acknowledged contribution to a plethora of cancers and other maladies in women who trustingly relied upon it for the relief of menopausal symptoms, Wyeth, and now Pfizer, shamelessly continue to promote the use of conjugated equine estrogens (CEEs) in their soon to be released Aprela® – the new panacea for postmenopausal women and men!
With the ever-growing aging population, the health and financial impact of osteoporosis in the United States and Canada may prove to be overwhelming without a concerted effort by the medical community to prevent and treat this debilitating disease.
Enter Aprela®
Designed as an alternative to combination estrogen/progestin therapy (i.e. Prempro®, Premphase®), Aprela® is a composite drug that claims to lessen menopausal symptoms while at the same time prevent or reduce the prevalence of bone loss in postmenopausal women reportedly without the elevated risk of estrogen-related cancers. A novel paradigm no less!
So what exactly is Aprela® and how does it differ from the Premarin® family of drugs, or for that matter, bona fide human estrogens?
Estrogen, Fuel for Feminine Survival: A Short Primer
The three major naturally occurring estrogens in women are estradiol (~10-20%), estriol (~60-80%) and estrone (~10-20%) all steroidal hormones produced in the body and derived from cholesterol through the actions of enzymes.[1] Note that these percentages are expressed as the amount typically circulating in the bloodstream and not within various tissues and organs in the body which can vary depending on numerous and complex biological processes.
Furthermore, the levels of human estrogens vary according to the state of the female body wherein estradiol is the strongest and principle estrogen present during reproductive years, estriol is the weakest and is found in large quantities during pregnancy and estrone tends to become elevated during postmenopausal years.[2] Unfortunately, the amount of estrone present after menopause is inadequate in superseding the operative loss of estradiol as one ages hence the symptoms of menopause develop. Here is where Big Pharma intervenes to exploit their market share monopoly and shameful profits without consequence to the survival of women and horses alike.
The principal dogma of the HRT industry is founded on the concept that the tissues of a postmenopausal woman are devoid of estrogen. This is simply not true. The concentration of a hormone in the blood is not directly correlated to the concentration in various organs.[3] It has been shown that when the concentration of progesterone (the pregnancy hormone) in the blood is high, the amount of estrogen in tissues declines and when there is a shortage of progesterone, the tissues retain estrogen, even when there is only a small amount of estrogen circulating in the blood.[4] In other words, it is the monthly cycling of progesterone levels during the reproductive years that helps regulate the amount of estrogen in various body tissues making sure that the concentration in the tissues is optimum during ovulation to enable conception. More importantly, when women reach menopause, a considerable reduction in progesterone levels occurs meaning that the tissues retain large amounts of estrogen on a continuous basis.[5]
Since estrogens are hormones, they function as signaling molecules. Estrogen signaling molecules circulate within the bloodstream and interact with a variety of “target” tissues such as the breast and uterus, the two main targets, but also the brain, liver, bone and heart.[6] Located within these target cells reside what are called estrogen receptors. It is here that the estrogen molecule attaches itself to the cell and eventually activates specific genes within the cell’s DNA to produce proteins that will influence the cell behavior in different ways. Normally, these proteins are beneficial to the tissues they affect.
For example:
- programming the breast and uterus for sexual reproduction,
- controlling cholesterol production in ways that limit the buildup of plaque in the coronary arteries, and
- preserving bone strength by helping to maintain the proper balance between bone buildup and breakdown[7].
