The Estrogen Connection

Most known risk factors for breast cancer involve some form of estrogen overexposure
  • The most abundant and important estrogen is called estradiol
  • Estradiol is so potent that its concentration in a woman's blood is measured in parts per trillion
  • When conception occurs, the corpus luteum generates enormous concentrations of progesterone and estradiol
  • The cells in the breast which are responsive to estradiol are those which are undifferentiated
  • It is the undifferentiated cells which are vulnerable to the effects of carcinogens
Why abortion dramatically raises a woman's risk of breast cancer
by Dr. Joel Brind, Ph.D.

According to 27 out of 31 studies, even one abortion increases the risk of getting breast cancer later in life.

Dr. Joel Brind, an endocrinology specialist, who has done a great deal of research on this issue and has compiled the results of the numerous studies, explains below the science behind the link.

His reports reveal an increased breast cancer risk of 50%, if an abortion is performed before the first live birth. If multiple abortions are performed the risk can increase up to 100%. He also explains how spontaneous miscarriages do not produce the same result.

Estrogen is the hormone that turns a girl's body into a woman's body at puberty. The most abundant and important estrogen is called estradiol which is so potent that its concentration in a woman's blood is measured in parts per trillion.

After puberty, the levels of estrogen rise and fall twice with each menstrual cycle. New egg-containing follicles develop in the ovaries during the first half of the menstrual cycle.

The follicular, estradiol-secreting cells surrounding the eggs proliferate, and so the ovaries secrete ever larger quantities of estradiol, reaching a peak about one day before ovulation.

This pre-ovulatory peak is the highest blood level of estradiol a woman ever normally experiences in the non-pregnant state.

After ovulation, the follicle which has expelled the egg After ovulation, the follicle which has expelled the egg becomes filled with another kind of cell called a luteal cell. These luteal cells proliferate under the influence of pituitary LH, thus secreting ever larger quantities of both estradiol and the pregnancy hormone progesterone, from which estradiol is made.

Since pituitary secretion of LH falls off quite sharply after ovulation, the corpus luteum (as the former follicle is now called) begins to regress, unless fertilization of the egg (conception) takes place. If conception has occurred, the embryo begins--almost immediately-- to secrete another chemical messenger which acts like LH to “rescue” the corpus luteum.

If rescued, the corpus luteum proceeds to generate enormous concentrations of progesterone and estradiol. By 7 to 8 weeks gestation, a pregnant woman’s blood already contains six times more estradiol than it did at the time of conception, more than twice the highest level attained in the non-pregnant state.
Cancer Cells Run Amok
How estradiol, or estrogens in general, relate to breast cancer risk, has to do with their role in the growth of breast tissue. It is estradiol which makes the breasts grow to a mature size at puberty, and which makes them grow again during pregnancy.

The cells in the breast which are responsive to estradiol are those which are primitive, or undifferentiated. Once terminally differentiated into milk-producing cells, breast cells can no longer be stimulated to reproduce.

It is the undifferentiated cells which can give rise to cancerous tumors later in life. If a woman therefore has gone through some weeks of a normal pregnancy, and then aborts that pregnancy, she is left with more of these cancer-vulnerable cells than she had in her breasts before she was pregnant.

In addition, any abnormal, potentially cancer-forming cells already in her breasts (present to some extent in all people) have also been stimulated to multiply.

All this translates into a statistically greater probability that a cancerous tumor may eventually arise. In fact most risk factors for breast cancer are attributable to overexposure to some form of estrogen.

In contrast, a full term pregnancy results in full differentiation of the breast tissue for the purpose of milk production, which leaves fewer cancer-vulnerable cells in the breasts than were there before the pregnancy began.

This translates into the well known breast cancer risk lowering effect of a full term pregnancy...

Most miscarriages occur in the first trimester, and over 90% of these are characterized by abnormally low maternal estradiol levels (quantities that do not exceed nonpregnant levels). One team of Swiss obstetricians, as far back as 1976, was actually able to predict miscarriages with 92% accuracy with just a single measurement of estradiol.

Theoretically, this makes perfect sense: the very reason for an early miscarriage is an inadequate supply of progesterone from which estradiol is made.

However, there is reason to believe that pregnancies which survive the first trimester (and they couldn’t survive without adequately high progesterone levels, which are paralleled by estradiol) are likely to raise breast cancer risk, if they go on to miscarry due to physical trauma or anatomic defect.

Since most miscarriages do occur in the first trimester, miscarriages generally have been found not to increase the risk of breast cancer.

Remember: reproductive rights are meaningless without the right of women to know all the consequences of the choices they may make.

Conception

If, however, conception has occurred and the corpus luteum has been rescued, it proceeds to generate enormous concentrations of progesterone and estradiol. Significantly elevated levels (compared to non-pregnant levels at the same time of the menstrual cycle) of estradiol can be detected as early as 5 days after conception.1

As shown in Figure 1, by 7-8 weeks gestation (after the last normal period) a pregnant woman's blood already contains six times more (i.e., 500% more) estradiol than it did at the time of conception, more than twice the highest level attained in the non-pregnant state (preovulatory peak).

In marked contrast, pregnancies destined to abort spontaneously (i.e., end in micarriage) during the first trimester usually do not generate estradiol in quantities exceeding non-pregnant levels.2,3

One team of Swiss obstetricians, as far back as 1976, was actually able to predict spontaneous abortions with 92% accuracy with just a single measurement of estradiol! The very reason for the miscarriage is an inadequate supply of progesterone from which estradiol is made.3

How does estradiol relate to breast cancer risk?

The relation of estradiol, or estrogens in general, to breast cancer risk has to do with their role in the growth of breast tissue. It is estradiol that makes the breasts grow to mature size at puberty and again during pregnancy (at least the first two trimesters).

The cells in the breast which are responsive to estradiol are those which are primitive, or undifferentiated. Once terminally differentiated into milk-producing cells, something which happens under the influence of other (still largely unknown) factors, breast cells can no longer be stimulated to reproduce.

                                              Figure 2

Schemetic representation of a breast a) in a never-pregnant woman, and b) at the end of a full-term pregnancy. Never pregnant breast tissue consists of primitive, terminal end bubs and ducts, which are vulnerable to carcinogens, while lactating breast consists mostly of mature lobules - clusters of milk-secreting alveoli - which are resistent to carcinogenc.

It is the undifferentiated cells, which are also vulnerable to the effects of carcinogens (radiation, certain chemicals, etc.), which can give rise to cancerous tumours later in life.

If a woman therefore has gone through some weeks of pregnancy, and then aborts that pregnancy, she is left with more of these cancer-vulnerable cells than she had in her breasts before she was pregnant.

In addition, any abnormal, potentially cancer-forming cells already in her breasts (and such cells are present to some extent in all people) have also been stimulated to multiply. All this translates into a statistically greater probability that a cancerous tumor may eventually arise.

In contrast, a full term pregnancy results in full differentiation of the breast tissue for the purpose of milk production, which leaves fewer cancer-vulnerable cells in the breasts than were there before the pregnancy began. This translates into the well known breast cancer risk lowering effect of a full term pregnancy.
Most known risk factors for breast cancer involve some form of estrogen overexposure.
For example, women who attain puberty at an early age, or who enter the menopause at a late age, or who have few or no children, are exposed to more surges of estradiol that come with more menstrual cycles.

Women who breast feed their children also experience fewer menstrual cycles, thereby helping to lower their risk.

Even risk factors which are unrelated to reproduction seem to operate via an estrogen-mediated mechanism. For example, post-menopausal obesity increases risk, presumably because adipose (fat) cells actually synthesise estrogens thus raising an obese woman's blood estrogen levels.

Chronic alcohol consumption also seems to raise breast cancer risk by increasing estrogen levels in a woman's blood.

Likewise for a diet high in animal fat, compared to a vegetarian diet. Conversely, certain vegetables known to help protect against cancer, such as members of the broccoli and cabbage family, help a woman's body to eliminate estrogens more rapidly.

Since the effect of estrogens on breast cancer risk has been well recognised for many years, doctors have been wary of prescribing such medications as post-menopausal estrogen replacement therapy for older women especially those with any family history of breast cancer.

One would think therefore, that doctors would long ago have been concerned about possible increases in breast cancer risk attributable to induced abortion, given the extremely high estradiol levels experienced by women even in the first several weeks of a normal pregnancy.

Finally, there is one additional and crucial aspect of spontaneous abortion vis-a-vis breast cancer risk that must be noted, namely the effect of post-first trimester miscarriages.

Most miscarriages occur in the first trimester, and over 90% of these are characterised by abnormally low maternal estradiol levels.3 However, there is reason to believe that pregnancies which survive the first trimester (and they couldn't survive without adequately high progesterone levels, which are parallelled by estradiol) are likely to go on to miscarry.

1 Stewart, et al J ClinEndoMetab 1993;76:1470-6
2 Witt, et al Fertil Steril 1990;53:1029-36
3 Kunz J, Keller PJ, Br J Ob Gyn 1976;83:640-4
The Breast Cancer Prevention Institute more