ESTROGEN AND THYROID in Hormone Harmony

ESTROGEN AND THYROID in Hormone Harmony

The thyroid gland and estrogen share a close and somewhat complicated
relationship. As on a seesaw, when one part is out of balance, it can readily throw the
other one off as well. For instance, while an increase in estrogen does not lower
production of thyroid hormones, it does cause a chain reaction that renders thyroid
hormones less active. Fortunately, millions of women have been helped by research
completed back in 1964, which established that adequate thyroid hormone helps
estradiol metabolize more completely into the “good” estrogen metabolite, 2-
hydroxyestrone (Fishman et al. 1965). Indeed, many, but not all, studies indicate that
having an underactive thyroid slows the process of clearing estrogen from the body,
thus creating a state of estrogen dominance, a known risk factor for breast cancer
(Vasudevan, Ogawa, and Pfaff 2002). Clearly, this is an area that requires significantly
more research and analysis. As always, we believe that balance is key: a thyroid gland
that works properly—that is neither hyperactive nor hypoactive—will help keep the
rest of your metabolism in balance. That is our goal!

ESTROGEN AND MELATONIN

Sleep habits also influence estrogen levels. Melatonin, the “sleep hormone” that
we produce when we sleep in complete darkness, helps reduce excessive estrogen
production. By simply sleeping in a completely dark room (and avoiding working
night shifts, if possible), you take another powerful step in keeping your estrogen levels
under control.

ESTROGEN, OBESITY, AND INSULIN

The current obesity epidemic has taken a toll on our hormonal balance, as
reported in numerous journals over the past decade, including the New England Journal
of Medicine (Yager and Davidson 2006) and the premier medical journal of the United
Kingdom, the Lancet (Bianchini, Kaaks, and Vainio 2002). As we discussed in chapter
6, obese women have a higher risk of developing breast cancer for a variety of reasons.
One key factor underlying this higher risk is an elevated level of circulating estrogens
that is linked to greater amounts of adipose (fat) tissue. Adipose tissue serves as an
additional site for estrogen production.

But there’s another hormone at play here as well. The liver produces a hormone
called sex hormone–binding globulin (SHBG), which carries sex hormones around the
body and regulates their access to tissues. In women, SHBG has a special affinity for
estradiol; that is, the more SHBG we have, the more estradiol is “bound up.” This is,
by and large, a good thing.

Obese women have lower levels of SHBG, making more estrogen available to
breast tissue. Perhaps most ominously, research published in the Journal of Clinical
Investigation showed that a high-fructose diet (containing high-fructose corn syrup, for
example, present in virtually all processed foods and beverages) decreased levels of
SHBG in the liver by a whopping 80 percent, resulting in higher levels of circulating
estrogen (Selva et al. 2007). Fortunately, a foundational Eating for Health plan, plus
the specific suggestions in next eplain, will go a long way toward helping manage
excess weight and insulin, and, in the process, controlling levels of estrogen and
SBGH.