Is Mammographic Breast Density Related To Blood Hormone Levels?

Mammographic breast density (MD) refers to the amount of breast and fibrous tissue seen on a mammogram compared to fatty tissue. For instance, the mammogram on the left shows mostly fatty tissue seen as primarily grey. On the other hand, the mammogram on the right indicates mostly bright white tissue and is dense. Breast density patterns are not new. Raul Leborgne first described breast density patterns in 1953! Over 20 years later, in 1976, John Wolfe from Weymouth University in England described in detail breast tissue patterns as seen on mammography. Over 40 years ago, he noticed and published data showing an increased risk of breast cancer with various mammographic patterns, most showing increased mammographic density.

It is now well-known women with dense mammographic patterns have a 4-6-fold increase in breast cancer risk compared to those with a more fatty replaced breast. There are several factors that we do know about MD. It is well known that mammographic density changes over time, with MD decreasing with age during a process known as breast involution. We also know that the typical breast cancer risk factors such as age at first pregnancy. We are also that MD decreases in time in women who undergo treatment with drugs that lower estrogen levels, such as tamoxifen. It is also well-known that women with a high BMI (BMI >25 is considered overweight) had a lower mammographic density. Calculate your own BMI at this website.

Whereas there is little controversy over the heightened risk of breast cancer, there is some question of whether hormone levels are involved in density patterns. A study from Sweden has been recently published that sheds some light on this subject.

The researchers studied serum hormone levels and mammographic patterns in over 1000 women. They found that although estrogen and prolactin (the lactation hormone) were associated with MD, high progesterone levels had the strongest association. The association of progesterone levels and breast density was not surprising. Progesterone plays a significant role in breast maturation and involution (decrease in size with a decline in function). The researchers also found that higher testosterone levels (male hormone) were associated with a MD decrease.
In summary, breast mammographic density is associated with an increased risk of breast cancer. Whereas breast density is in part an inheritable factor, it is also dependent on a woman’s BMI, age, and menopausal status. It is also related, at least partially, to blood hormone levels. Most importantly, women with higher progesterone levels are more prone to show a dense breast pattern on their mammograms.