Thursday, October 21, 2004

Pill Cuts Cancer, Coronary Risk

The same huge federal study that led millions of women to abandon use of hormones after menopause now provides reassurance that another hormone concoction - the birth control pill - is safe.

In fact, women on the pill had surprisingly lower risks of heart disease and stroke and no increased risk of breast cancer, contrary to what many previous studies have found.

The study in question is the Women's Health Initiative (WHI), and the American Society for Reproductive Medicine's press release is here.

The article mentions one possible explanation for how Pill use lowers the risk of heart disease:

Studies in animals suggest that estrogen may reduce inflammation in the bloodstream and help prevent deposits from forming and blocking vessels, [Dr.] Victory said.

Another possible mechanism is the Pill's effect on hemoglobin levels.

Some researchers suspect that the crucial oxygen-carrying protein in blood, hemoglobin, may also be important. Women tend to have less hemoglobin than men because of their monthly menstrual cycles, and low hemoglobin may further starve the heart muscle....

"Hemoglobin turns out to be a major independent predictor of outcome," [Dr.] Pepine said.

Women who use the Pill have higher hemoglobin levels (less blood loss) than nonusers.

The article also touches on the difference between women being exposed to the Pill's hormones, and the hormones used in combination hormone therapy (CHT, old name HRT):

"Those women went for a prolonged period of time without estrogen and then were re-exposed to estrogen" when they took so-called hormone replacement therapy after menopause, [Dr.] Victory said.

This is a crucial difference, and one of the main reasons you can't extrapolate hormone use findings from one population (reproductive-age women) to another (postmenopausal women).

Reproductive-age women continuously produce estrogen (E) (and progesterone). In women who use the Pill, the body's E is replaced by the Pill's E; there's a net hormone substitution (no hormone addition or deficiency). In contrast, postmenopausal women no longer produce E. In women who use HRT, the HRT's E is added to the body; there's a net hormone addition.

If you'd like more information about the HRT studies, I have a list of links on my book site (please pardon the appearance, it's still under construction).


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