Hormones serve as our body’s chemical messengers to help maintain homeostasis, or state of balance.  They originate in one area and act on another (target cell), usually transmitted through bodily fluid such as blood.

I tend to visualize a New York City bicycle courier dashing around the congested streets to deliver a package in a timely manner when I think of the this signaling pathway we call the endocrine system. Much like the courier uses landmarks to determine his target, hormones hone in on cell signals and receptors.


Although both estrogen and thyroid hormones, thyroxine (T4) and triiodothyronine(T3) they have different chemical classifications. Estrogen belongs to the class of steroid, lipid or sex hormones. Steroid hormone, which are usually ketones or alcohols and are insoluble in water, or hydrophobic (think oil in water). They often end in ‘-ol’ or ‘-one’. Meanwhile, thyroid hormones are considered amino acid derived hormones (ending in ‘-ine’). These types of hormones are water soluble, or hydrophilic.

Although men have estrogen and it is important for proper sexual function, cardiovascular and brain health, it is typically thought of as a female hormone (1,2)

So How Exactly Does Estrogen Affect Thyroid Function?

T3 is the most metabolically active thyroid hormone in the body. Remember, it must be converted from T4 in peripheral organs such as the liver and kidneys. When estrogen is present in unbalanced quantities, it can affect thyroid function in three main ways:

thyroid birth control

Blocks the Conversion of T4 to T3

My previous article, Functional Thyroid Treatment in Miami, gives an overview of the thyroid and its’ associated hormones. Although the thyroid gland mostly produces T4, it must be converted to more metabolically active form, T3, but peripheral tissues such as found in the liver and kidneys. Prolonged, elevated levels of estrogen may inhibit the optimal conversion to this active form.

Elevates Thyroid Binding Globulin

There is some evidence that elevated estrogen may increase thyroid binding hormone. When TBG is high, it grabs onto active thyroid hormone and reduces their ability to interact with the cell, thereby effectivly lowering free thyroid. Considering hormonal birth control contains synthetic estrogens then this may also affect thyroid function (7,8). 

As a side note, many hormonal birth control pills contain lactose and gluten as binders/fillers. Those with Hashimoto’s thyroiditis or intolerances to these substances should be aware.

Higher Thyroxine While on Estrogen Replacement

A study published in the June edition (2001) edition of the New England Journal of Medicine (9) concluded that women treated with thyroxine (T4) and estrogen therapy may require a higher doese of thyroxine.  The author goes on further to state women with hypothyroidism need an average of 45 percent more thyroxine during pregnancy to maintain euthyroidism.


Estrogen and Thyroid 

Conversion Factors

Menopause and Your Thyroid

The incidence of thyroid disorders is most prevalent amongst post menopausal women (4). Since many symptoms of thyroid disorders may overlap with those of menopause, as outlined in Table 1, it is an often overlooked problem. Left unchecked this can lead to a host of other comorbities such as increased cardiovascular risk, depression, bone fractures and cognitive impairment. Care should be exercised when using thyroid medications in the 50+ population as an excess can lead to arrythmia’s, hence the necessity of a good cardio work-up.

Table 1: Symptoms of Menopause vs Hypothyroidism

hot flash and night sweatsincreased sensitivity to cold
irregularities in the lower urinary tract, such as frequent urination or excessive urination at nighthigher levels of blood lipids, such as triglycerides and cholesterol
disturbed sleepslower heart rate
problems focusing and learningpoor memory
changes in energy or feelings of fatiguepersistent fatigue or feelings of being tired
changes in body weight, such as a sudden increase in weightincrease in body fat
vulvovaginal atrophy and drynessweakness in muscles and joints
cessation of menstrual cyclesthinning of head hair
mood swingsdepression or sadness
dry, chapped skin

Miami Thyroid Consultations

To see me as a patient in my Brickell, Miami office or telemedicine consultation, please call 305-448-2600 or email us at [email protected] to schedule.


1. Schulster M, Bernie AM, Ramasamy R. The role of estradiol in male reproductive function. Asian J Androl. 2016;18(3):435‐440. doi:10.4103/1008-682X.173932,

2. Jankowska EA, Rozentryt P, Ponikowska B, et al. Circulating Estradiol and Mortality in Men With Systolic Chronic Heart Failure. JAMA. 2009;301(18):1892–1901. doi:10.1001/jama.2009.639)

3. Mazer NA. Interaction of estrogen therapy and thyroid hormone replacement in postmenopausal women. Thyroid. 2004;14 Suppl 1:S27‐S34. doi:10.1089/105072504323024561

4. Gietka-Czernel M. (2017). The thyroid gland in postmenopausal women: physiology and diseases. Przeglad menopauzalny = Menopause review16(2), 33–37. https://doi.org/10.5114/pm.2017.68588

5. Santin AP, Furlanetto TW. Role of estrogen in thyroid function and growth regulation. J Thyroid Res. 2011;2011:875125. doi:10.4061/2011/875125

6. Conde, S. J., Luvizotto, R., de Síbio, M. T., & Nogueira, C. R. (2014). Thyroid hormone status interferes with estrogen target gene expression in breast cancer samples in menopausal women. ISRN endocrinology, 2014, 317398. https://doi.org/10.1155/2014/317398

7. Wiegratz I, Kutschera E, Lee JH, et al. Effect of four oral contraceptives on thyroid hormones, adrenal and blood pressure parameters. Contraception. 2003;67(5):361‐366. doi:10.1016/s0010-7824(03)00006-4

8. Kenneth B. Ain, Samuel Refetoff, David H. Same, and Yoshiharu Murata. Effect of Estrogen on the Synthesis and Secretion of Thyroxine-Binding Globulin by a Human Hepatoma Cell Line, HEP G2

9. Arafah, Baha (2001)Increased Need for Thyroxine in Women with Hypothyroidism during Estrogen Therapy. N Engl J Med 2001; 344:1743-1749