Estrogen is the hormone that regulates the sexual and reproductive development that occurs in women, most noticeably at puberty. When a woman goes through menopause, her estrogen production declines dramatically, resulting in symptoms such as hot flashes and insomnia.
But other changes are occurring as well. As the amount of female estrogen goes down, cholesterol levels shift in a bad direction — harmful LDL cholesterol goes up, while so-called “good” HDL cholesterol declines.
Female muscle mass also declines and bones can become brittle because estrogen plays a key role in bone growth and stability.
When a woman is thrust into premature menopause due to the removal of her ovaries or as a consequence of cancer treatment, she should take hormone replacements. There’s no question about that.
But what about the woman whose estrogen declines naturally? Should she be treated as well? This is a controversy that has simmered for years.
There are several different types of treatment available, but in general they fall into two major types: estrogen replacement therapy (ERT) and hormone replacement therapy (HRT).
ERT, the first type of hormone replacement that came into use, is pure estrogen. But in the 1970s, it was discovered that pure estrogen, when used by a woman who still has her uterus, increases the risk of uterine (endometrial) cancer.
Soon after that, HRT — a combination of estrogen and progesterone (the other hormone produced during the menstrual cycle) — came into use. It is now the most popular form of female hormone replacement.
Women’s risk of heart disease begins to rise dramatically after menopause, when estrogen levels dip, as was shown by many observational studies over the course of several decades.
In the 1990s, the Women’s Health Initiative (WHI), a large-scale study, was launched to learn if giving women estrogen after menopause would protect their hearts. The participants were divided into three groups: One group received ERT, the other group HRT, and the results of both were compared to a group that had not received hormones but were given a placebo instead.
The results shocked the medical community. Instead of being protected from heart disease, the women who took HRT were at greater risk for heart attack, stroke, blood clots, breast cancer, and dementia.
Although the women who took estrogen alone experienced less risk of adverse events, the hormones did not protect their hearts.
In fact, under some circumstances, the hormone therapy actually increased the risk of heart attack, stroke, and breast cancer.
News of the results caused a major shift in national health guidelines.
Prior to the study, most doctors were not reluctant to put women on long-term hormone replacements.
But after the results were published, doctors’ prescription habits changed. They were advised to offer hormone replacement therapy only for women suffering severe postmenopausal symptoms — and then to prescribe them for the shortest duration possible.