Progesterone and Thyroid Relationship

Thyroid may be a small, butterfly-shaped gland, but it takes part in a number of processes in the body.

The function of the thyroid gland is influenced by many factors including hormones.

One of our previous articles discussed the link between estrogen and thyroid health, but in this post, we are going to focus on a relationship between progesterone and thyroid.

How is this hormone connected to the functioning of the thyroid gland?

You’ll find answers below.

Role of progesterone

Progesterone is a female hormone produced by the corpus luteum in the ovary during ovulation or the process when a mature egg is released. The hormone regulates and stimulates numerous functions in the body including ovulation and it plays a vital role during pregnancy[i].

The primary function of progesterone is to prepare endometrium (lining of the uterus) to receive the egg if it gets fertilized by sperm. In instances when an egg isn’t fertilized, progesterone levels decline and cause menstrual bleeding.

During a woman’s pregnancy, progesterone supports the growth of milk-producing glands in the breasts and teenage girls need the hormone for breast development[ii].

Even though the hormone is mainly produced in corpus luteum in the ovary, certain quantities are made by ovaries themselves, adrenal glands, and placenta (during pregnancy)[iii].

Besides its role in pregnancy and female menstrual cycle, progesterone has many other benefits. The hormone exhibits anti-inflammatory effects, regulates blood pressure, protects bone health, improves mood and reduces anxiety, supports fertility, aids weight loss, among other things[iv].

Sufficient levels of progesterone are necessary for balance in estrogen. Bearing in mind that estrogen has a strong relationship with thyroid health and function, it’s impossible not to wonder how progesterone affects the way this gland operates.

Progesterone deficiency and autoimmune thyroid disease

Autoimmune thyroid diseases occur when a person’s immune system starts attacking the thyroid and its tissues thus disrupting production of hormones.

Two types of autoimmune thyroid disease have been identified: Graves’ disease (the most common cause of hyperthyroidism) and Hashimoto’s thyroiditis (leads to hypothyroidism).

Numbers show that rates of Hashimoto’s thyroiditis are increasing each year. At this point, about 3-5 cases per 10,000 people are diagnosed every year. Women are more likely to develop this autoimmune condition with ratio 20:1 compared to men[v].

Why is the prevalence of Hashimoto’s thyroiditis among women so important? That’s because the balance of progesterone and estrogen plays a role in the development of this condition.

The journal Endocrine Research published a study which discovered that Hashimoto’s thyroiditis is prevalent among women with polycystic ovary syndrome (PCOS). Polycystic ovary syndrome is a condition that affects women’s hormone levels.

Scientists found that women with PCOS had elevated levels of TSH (thyroid stimulating hormone) and low levels of progesterone.

They concluded the study explaining that higher prevalence of Hashimoto’s thyroiditis among women with PCOS could be related to an imbalance of estrogen-progesterone ratio[vi]. Since progesterone deficiency correlates with disturbed thyroid hormone levels, it’s easy to understand that low concentration of this hormone impairs thyroid function.

Progesterone plays a role in estrogen dominance

The equilibrium between estrogen and progesterone is vital for optimal sexual and overall health and wellbeing.

Only when the body contains sufficient amounts of both hormones will reproductive system and other functions in the body work properly. The relationship between two hormones, i.e. their balance, is crucial for thyroid health too.

Evidence shows that estrogen increases the production of thyroid-binding globulin[vii], a protein which binds thyroid hormone and makes it inactive. This leads to decreased metabolism and increased fat deposits.

On the other hand, progesterone decreases thyroid binding globulin and increases the activity of thyroid hormones, when sufficient amount of this hormone is present in the body. The proper activity of thyroid hormones accelerates metabolism and uses the fat that was stored under estrogen influence for an energy boost[viii].

The equilibrium of estrogen and progesterone is also vital for the prevention of estrogen balance. High estrogen or estrogen balance is a common problem wherein an affected woman can have normal or excessive levels of estrogen, but the insufficient amount or no progesterone. What’s more, women with low estrogen levels can develop estrogen dominance if they don’t have progesterone in the body.

Estrogen dominance urges liver to produce more thyroid binding globulin (TBG). As stated above, enhanced production of TBG decreases the amount of thyroid hormone.

What happens then?

Suppressed production of much-needed thyroid hormones leads to hypothyroidism.

Hypothyroidism and estrogen dominance have numerous symptoms in common such as hair loss, weight gain, fatigue, headache, low libido, among others. In fact, thyroid problems can also be a symptom of estrogen dominance[ix] thus confirming the impact of hormone imbalance (low progesterone and high estrogen) on the function of thyroid gland.

Effects of estrogen dominance on thyroid hormones can also extend to mental, not just physical health. Suppressed production of thyroid hormones due to hypothyroidism can contribute or aggravate symptoms of depression.

Studies show that hypothyroid women are predisposed to depressive symptoms regardless of socioeconomic and demographic factors[x].

Here’s what exactly happens, production of progesterone declines and body responds by releasing more estrogen and liver starts pumping out more TBG. In turn, the amount of hormone T3 is limited and becomes unavailable to cells that need it to function properly.

The limbic system (brain structures including hypothalamus, amygdala, thalamus, hippocampus etc.) is strongly deprived of T3 and consequences are felt in levels of serotonin and norepinephrine.

As a result, you feel sad, depressed, and uninterested in activities you used to enjoy[xi].

Progesterone receptors in thyroid

Hormone fluctuations are natural and they affect everyone, but as you age their levels start to decline. As you know now, progesterone deficiency affects the way thyroid functions. Low levels of this hormone induce estrogen dominance-like symptoms which affect thyroid not only due to TBG levels but because thyroid contains progesterone receptors.

Progesterone receptors bind with the hormone and the gland responds by producing T3 and T4. When progesterone deficiency occurs, the hormone is unable to bind to receptors in the thyroid gland.

The result is obvious: production of thyroid hormones decreases and an affected person experiences thyroid symptoms that are very similar to estrogen dominance/low progesterone[xii].

Speaking of progesterone receptors in thyroid, the Journal of Endocrinological Investigation published a study which investigated the role of Vitamin D and progesterone receptors in papillary thyroid carcinoma (PTC).

Papillary carcinoma is the most prevalent form of well-differentiated thyroid cancer and the most common type of the disease occurring due to exposure to radiation. A team of scientists from Greece found that vitamin D receptors and protein expression were higher in PTC compared to non-neoplastic thyroid tissue.

Progesterone receptors mRNA was increased in 34% participants. Interestingly, findings revealed that progesterone receptors and not vitamin D receptor expression were strongly associated with tumor size[xiii].

Healthy thyroid influences progesterone

Throughout this post, we discussed the impact of low progesterone on thyroid function. Every relationship is a two-way street, progesterone and thyroid aren’t the exceptions here. Just like a deficiency in this hormone affects the production of thyroid hormones, this small gland in your neck influences production of progesterone.

The Journal of Endocrinology featured a study which found that T3 significantly stimulated the release of progesterone from luteal cells. That being said, T3 stimulation of progesterone release from luteal cells isn’t direct.

Instead, progesterone release is mediated through a putative protein factor[xiv]. Luteal cells are cells from the corpus luteum, an endocrine structure in female ovaries, and the primary location of progesterone production as stated above.

In other words, proper function of thyroid gland is necessary for production and sufficient levels of progesterone. Thyroid and progesterone go hand in hand and work properly only when their functions are balanced.

Progesterone is anti-inflammatory

Inflammation plays a big role in autoimmune conditions affecting the thyroid. Let’s take Hashimoto’s thyroiditis as an example; the term thyroiditis refers to the inflammation of thyroid gland[xv], according to the American Thyroid Association.

A growing body of evidence confirms that oxidative stress is a significant mechanism underlying the progress of inflammation. Both conditions (inflammation and oxidative stress) create a vicious circle that affects your entire health and wellbeing. Thyroid hormones protect the body from joint influence of oxidative damage and inflammation due to their antioxidant role. Of course, this only occurs when production of hormones is sufficient. Hypothyroidism can aggravate oxidative stress and cause a chain of reactions that only increases inflammation and suppressed production of hormones[xvi].

It’s a little-known fact that progesterone exhibits anti-inflammatory effects by suppressing NF-κB (pro-inflammatory signaling protein) and MAPK (contributes to a pro-inflammatory response) activation. Basically, progesterone can attenuate inflammation by inhibiting pro-inflammatory pathways and mediator expressions[xvii].

Getting progesterone levels checked

Due to the importance of progesterone for proper function of thyroid gland, it’s useful get levels of this hormone tested. This is particularly important if you’re experiencing symptoms associated with thyroid disorders or you’re already diagnosed with a condition affecting this gland. Testing progesterone levels is important for men too.

Why? The hormone is involved in the creation of sperm i.e. spermatogenesis.

In order to check levels of progesterone in your body, the doctor will order a serum progesterone test. The test requires a blood sample of a patient. Before progesterone levels are checked, it’s useful to inform the doctor about medications you’re taking because some drugs may affect the amount of this hormone in your body.

Serum progesterone level is measured in nanograms per deciliter (ng/dL). The laboratory analyzes the blood sample and sends results to your doctor. What is considered to be a normal level of progesterone tends to vary as it depends on a patient’s age, gender, menstrual cycle, pregnancy.

Generally speaking, men, postmenopausal women, and women who are at the beginning of their monthly cycle have 1 ng/mL or under.

The normal range of progesterone in women who are in the middle of their menstrual cycle is 5-20 ng/mL.

Healthy levels of progesterone in pregnant women depend on the stage of the pregnancy.

For example, the normal range of progesterone in the first trimester is 11.2 to 90 ng/mL, in the second trimester, the amount goes from 25.6 to 89.4 ng/mL, while in the third trimester healthy levels of this hormone are between 48.4 and 42.5 ng/mL.

Should I use progesterone?

Women whose hormones are declining have the opportunity to use the bioidentical or synthetic hormone to replenish the loss of progesterone and improve thyroid function.

At this point, there’s no exact evidence that proves efficacy or inefficacy of hormone intake. If you look online, you’ll notice some sources advise against intake of progesterone while others promote it. The best thing to do is to consult your doctor.

Your physician will let you know whether you should take progesterone for better thyroid health.

Conclusion

Healthy levels of progesterone are vital for your overall health and wellbeing. The thyroid is strongly connected to the concentration of progesterone.

At the same time, the hormone depends on the function of thyroid gland because it can stimulate progesterone release.

More research is important to uncover the relationship of this hormone and thyroid in full detail.

References

[i] Progesterone, WebMD https://www.webmd.com/women/progesterone-15286#1

[ii] Blanchette, S., et al. “Circulating Progesterone and Obesity in Men.” Hormone and Metabolic Research = Hormon- Und Stoffwechselforschung = Hormones Et Metabolisme, vol. 38, no. 5, May 2006, pp. 330–35. PubMed, doi:10.1055/s-2006-925392.

[iii] Progesterone, YourHormones.info http://www.yourhormones.info/Hormones/Progesterone.aspx

[iv] Bhatia, A. J., and G. N. Wade. “Progesterone Can Either Increase or Decrease Weight Gain and Adiposity in Ovariectomized Syrian Hamsters.” Physiology & Behavior, vol. 46, no. 2, Aug. 1989, pp. 273–78.

[v] Zaletel, Katja, and Simona Gaberšček. “Hashimoto’s Thyroiditis: From Genes to the Disease.” Current Genomics, vol. 12, no. 8, Dec. 2011, pp. 576–88. PubMed Central, doi:10.2174/138920211798120763.

[vi] Arduc A, Aycicek Dogan B, Bilmez S, et al. High prevalence of Hashimoto’s thyroiditis in patients with polycystic ovary syndrome: does the imbalance between estradiol and progesterone play a role? Endocrine Research 2015 Mar;40(4):204-210. Doi: 10.3109/07435800.2015.1015730 http://www.tandfonline.com/doi/abs/10.3109/07435800.2015.1015730?journalCode=ierc20

[vii] Ben-Rafael Z, Struass JF 3rd, Arendash-Durand B, et al. Changes in thyroid function tests and sex hormone binding globulin associated with treatment by gonadotropin. Fertility and Sterility 1987 Aug;48(2):318-320. Doi: 10.1016/S0015-0282(16)59363-7 http://europepmc.org/abstract/med/3111894

[viii] Estrogen and progesterone: two important hormones, TaylorMedicalGroup.net https://taylormedicalgroup.net/hormones/estrogen-and-progesterone

[x] Zavareh AT, Jomhouri R, Bejestani HS, et al. Depression and hypothyroidism in a population-based study of Iranian Women. Romanian Journal of Internal Medicine 2016 Dec 1;54(4):217-221. Doi: 10.1515/rjim-2016-0033 https://www.ncbi.nlm.nih.gov/pubmed/28002033

[xi] Santin, Ana Paula, and Tania Weber Furlanetto. “Role of Estrogen in Thyroid Function and Growth Regulation.” Journal of Thyroid Research, vol. 2011, May 2011. PubMed Central, doi:10.4061/2011/875125.

[xii]Kumar, Pratap, and Navneet Magon. “Hormones in Pregnancy.” Nigerian Medical Journal : Journal of the Nigeria Medical Association, vol. 53, no. 4, 2012, pp. 179–83. PubMed Central, doi:10.4103/0300-1652.107549.

[xiii] Yavropoulou MP, Panagiotou G, Topouridou K, et al. Vitamin D receptor and progesterone receptor protein and gene expression in papillary thyroid carcinomas: associations with histological features. Journal of Endocrinological Investigation 2017 Dec;40(12):1327-1335. Doi: 10.1007/s40618-017-0700-4 https://www.ncbi.nlm.nih.gov/pubmed/28589382

[xiv] Datta M, Roy P, Banerjee J, Bhattacharya S. Thyroid hormone stimulates progesterone release from human luteal cells by generating a proteinaceous factor. Journal of Endocrinology 1998 Sep;158(3):319-25 https://www.ncbi.nlm.nih.gov/pubmed/9846161

[xv] Thyroiditis, American Thyroid Association https://www.thyroid.org/thyroiditis/

[xvi] Mancini A, Di Segni C, Raimondo S, et al. Thyroid Hormones, Oxidative Stress, and Inflammation. Mediators of Inflammation. 2016;2016:6757154. doi:10.1155/2016/6757154. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4802023/

[xvii] Lei B, Mace B, Dawson HN, Warner DS, Laskowitz DT, James ML. Anti-Inflammatory Effects of Progesterone in Lipopolysaccharide-Stimulated BV-2 Microglia. Peterson KE, ed. PLoS ONE. 2014;9(7):e103969. doi:10.1371/journal.pone.0103969. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4117574/

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