Estrogen Dominance and Hypothyroidism
Hypothyroidism affects women seven times more frequently than men.
The epidemic of estrogen dominance among women is likely at the core of
this disparity. Excess estrogen levels or “estrogen dominance” causes
the liver to produce high levels of thyroid binding globulin (TBG),
which, as its name suggests, binds the thyroid hormone and decreases the
amount of thyroid hormone that can be assimilated and utilized by the
cells.
Women with estrogen dominance may have a normally functioning thyroid
gland that produces adequate amounts of thyroid hormone, however,
because the hormone is inactivate when bound to TBG, little functional
action is available at a cellular level and symptoms can present as if
clinical hypothyroidism was present. Moreover, symptoms of
hypothyroidism and estrogen dominance often overlap with weight gain,
fatigue, low libido, hair loss, difficult cognition, low mood and
irregular menstruation.
Estrogen Dominance Made Worse
Hormonal contraception, pregnancy, and synthetic estrogens prescribed
during and after menopause exacerbate estrogen dominance and increase
levels of TBG. It is also important to remember the exacerbation of
estrogen dominance in hypothyroidism. Estrogen must first be made water
soluble by the liver in order to be eliminated from the body.
Hypothyroidism hinders the effectiveness of this this elimination
pathway through the liver. This results in a buildup of proliferative
estrogen, increasing risk of pathologies such as breast cancer, uterine
fibroids and ovarian cysts.
More Evidence
To further illustrate the connection between estrogen dominance and
low thyroid function, consider polycystic ovary syndrome (PCOS), a
metabolic disorder often resulting in anovulatory cycles and estrogen
dominance. Progesterone is a hormone produced by the corpus luteum upon
ovulation and functions to balance the effects of estrogen. Anovulation
results in insufficient progesterone production and therefore, ongoing
estrogen dominance. Endocrine Research published a study which
found that Hashimoto’s thyroiditis, clinical hypothyroidism of an
autoimmune nature, is highly prevalent among women with PCOS. They
concluded that “Increased estrogen and the estrogen/progesterone ratio
seem to be directly involved in high anti-TPO levels in PCOS patients.”
A study published in Molecular Cellular Endocrinology
revealed 2- Methoxy estradiol, an endogenous estrogen metabolite
“induced dramatic changes in (thyroid) cell morphology and decreased the
viability of the cells, as well as disrupted the structural integrity
of cultured thyroid follicles.” They found that this process results in
the release of thyroid antigens that may play a role in high incidence
of thyroid autoantibodies and autoimmune thyroid disease in women.
Estrogen Replacement Therapy
Yet another study correlating estrogen dominance and hypothyroidism from the journal Thyroid,
found that oral estrogen therapy increases thyroxine dosage
requirements in hypothyroid women, due to increased TBG and subsequent
lower levels of free thyroxine. On a positive note, transdermal estrogen
therapy was not found to affect TBG levels and therefore may be the
preferred therapy for postmenopausal women who require concomitant
treatment with estrogen and thyroid replacement.
Friendly Progesterone
To contrast the effect of estrogen on thyroid hormone, progesterone
decreases TBG and increases the activity of thyroid hormones when
present in adequate levels. Thyroid hormones, like progesterone, have a
thermogenic effect on the body, accelerating metabolism and utilizing
fat for energy production. The Journal of Endocrinology featured
a study showing triiodothyronine (T3) significantly stimulated the
release of progesterone from luteal cells. Furthermore, research
published in Clinical Endocrinology concluded that progesterone
therapy increases free thyroxine (T4). Additionally, progesterone
exhibits anti-inflammatory effects, regulates blood pressure, protects
bone health, improves mood and reduces anxiety, supports fertility, and
aids weight loss.
Summary
Though the thyroid is a small, butterfly-shaped gland, its impact on
the body is anything but minute and delicate. When treating patients for
hormonal imbalances, it is imperative to understand the complex
interplay between thyroid hormones and sex hormones. The research
summarized in this article illustrates that improving the issues of
estrogen dominance by decreasing excess estrogen levels and by
supporting healthy progesterone levels, will also provide benefits for
thyroid hormones.
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