Like all interacting components of the neuroendocrine system, the thyroid gland and the hormone estrogen are engaged in a carefully-choreographed dance. When the rhythm is right, these two elements interact in a dance that ensures proper functioning of many bodily functions.
The thyroid controls metabolism and body temperature, while estrogen influences fat storage and the development and regulation of the female reproductive system.
Estrogen Dominance in Hormonal Birth Control and Menopause
In some situations, such as with the use of hormonal birth control and in menopause, estrogen levels can become disturbed. This is called estrogen dominance when there is not enough progesterone to properly balance with either low, normal, or high estrogen. Estrogen dominance is characterized by:
- mood swings
- irritability
- low mood
as well as
- irregular periods
- heavy bleeding
- dysmenorrhea
- ovarian cysts
- vaginal dryness
- poor sleep
- fatigue
- weight gain
Estrogen dominance, or imbalanced estrogen levels, can be harmful to the thyroid; estrogen and thyroid’s dance becomes out of sync. Thyroid function depends on sufficient thyroid hormones circulating in the bloodstream.
Thyroid binding globulin, or TBG, binds to thyroid hormones and carries them through the blood. When TBG is elevated, there is more thyroid hormone bound to it; thus, there is less active thyroid hormone available to perform thyroid functions. When the thyroid cannot perform its dance, symptoms occur, such as:
- weight gain, fatigue
- decreased libido
- poor memory
- low mood
may arise.
Estrogen and Increased TBG
Estrogen is known to increase TBG, but it does not raise levels of the hormone that stimulates thyroid, or increase active thyroid hormone. [1, 3, 6, 8, 10, 11]
Research shows that estrogen-containing oral contraceptives can increase TBG and lower active free thyroid hormone. [4, 7, 13]
Hormone replacement therapy (HRT) using estrogen can also cause increases in TBG. [2, 9] The increase of estrogen and TBG disrupts the thyroid and may contribute to autoimmune thyroid disease. [12]8
Many people depend on estrogen through oral contraceptives or HRT, or naturally have more estrogen than progesterone, as seen in menopause. Research shows that using transdermal methods may be the solution.
Transdermal estrogen therapy doesn’t elevate TBG levels; therefore, it is unlikely that this method would negatively affect thyroid function. [5]
Balance Sex Hormones and Thyroid Hormones
In summary, the dance of thyroid and estrogen depends on a careful equilibrium of sex hormones and thyroid hormones. Imbalanced estrogen can suppress the thyroid and cause unwanted symptoms such as:
- weight gain
- low mood
- fatigue
In menopause, this decreased thyroid function due to estrogen can be avoided through use of transdermal estrogen. Assessing the thyroid and sex hormones can help identify imbalances and guide treatment to maintain homeostasis, especially in the delicate dance of the thyroid and estrogen.
References
1. Ågren, U. M., Anttila, M., Mäenpää-Liukko, K., Rantala, M. L., Rautiainen, H., Sommer, W. F., & Mommers, E. (2011). Effects of a monophasic combined oral contraceptive containing nomegestrol acetate and 17β-oestradiol compared with one containing levonorgestrel and ethinylestradiol on haemostasis, lipids and carbohydrate metabolism. The European Journal of Contraception & Reproductive Health Care,16(6), 444-457.
2. Benencia, H., Ropelato, M. G., Rosales, M., Mesch, V., Siseles, N., Boero, L., … & Dourisboure, R. (1998). Thyroid profile modifications during oral hormone replacement therapy in postmenopausal women. Gynecological Endocrinology, 12(3), 179-184.
3. Ceresini, G., Morganti, S., Rebecchi, I., Bertone, L., Ceda, G. P., Bacchi-Modena, A., … & Braverman, L. E. (2004). A one-year follow-up on the effects of raloxifene on thyroid function in postmenopausal women. Menopause, 11(2), 176-179.
4. Grüning, T., Zöphel, K., Wunderlich, G., & Franke, W. G. (2006). Influence of female sex hormones on thyroid parameters determined in a thyroid screening. Clinical laboratory, 53(9-12), 547-553.
5. Mazer, N. A. (2004). Interaction of estrogen therapy and thyroid hormone replacement in postmenopausal women. Thyroid, 14(3, Supplement 1), 27-34.
6. Mueck, A., Neulen, J., Thaler, C., Birkhäuser, M., Braendle, W., Kiesel, L., & Kuhl, H. (2009). [Contraception in women with special problems].Therapeutische Umschau. Revue therapeutique, 66(2), 117-128.
7. Raps, M., Curvers, J., Helmerhorst, F. M., Ballieux, B. E., Rosing, J., Thomassen, S., … & van Vliet, H. A. (2014). Thyroid function, activated protein C resistance and the risk of venous thrombosis in users of hormonal contraceptives. Thrombosis research, 133(4), 640-644.
8. Sänger, N., Stahlberg, S., Manthey, T., Mittmann, K., Mellinger, U., Lange, E., … & Wiegratz, I. (2008). Effects of an oral contraceptive containing 30 mcg ethinyl estradiol and 2 mg dienogest on thyroid hormones and androgen parameters: conventional vs. extended-cycle use. Contraception,77(6), 420-425.
9. Schindler, A. E. (2003). Thyroid function and postmenopause. Gynecological endocrinology, 17(1), 79-85.
10. Tahboub, R., & Arafah, B. M. (2009). Sex steroids and the thyroid. Best Practice & Research Clinical Endocrinology & Metabolism, 23(6), 769-780.
11. Toldy, E., Löcsei, Z., Rigo, E., Kneffel, P., Szabolcs, I., & Kovacs, G. L. (2004). Comparative analytical evaluation of thyroid hormone levels in pregnancy and in women taking oral contraceptives: a study from an iodine deficient area. Gynecological endocrinology, 18(4), 219-226.
12. Wang, S. H., Myc, A., Koenig, R. J., Bretz, J. D., Arscott, P. L., & Baker, J. R. (2000). 2-Methoxyestradiol, an endogenous estrogen metabolite, induces thyroid cell apoptosis. Molecular and cellular endocrinology,165(1), 163-172.
13. Westhoff, C. L., Petrie, K. A., & Cremers, S. (2013). Using changes in binding globulins to assess oral contraceptive compliance. Contraception, 87(2), 176-181.
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