High Progesterone and Thyroid Connection

High Progesterone and Thyroid Connection

Hormones are chemical messengers that regulate various functions in the body.


Our health and wellbeing depend on the balance of these hormones. However, they do not remain constant. Concentrations of various hormones fluctuate due to biological and other reasons such as lifestyle.


Excessive or low amounts of a certain hormone affect different systems in the body but also the functionality of other glands. Progesterone is one of those hormones.


In this post, we are going to focus on the impact of high progesterone on the thyroid gland.


What does progesterone do?

Progesterone is a steroid hormone from the class of hormones called progestogens. The hormone is secreted by ovaries in the corpus luteum, placenta, and adrenal glands.


The primary function of progesterone is to regulate the condition of the endometrium (inner lining of the uterus). This hormone prepares the wall of the uterus so that the endometrium can accept the fertilized egg. That way, the egg can be implanted and start developing. Additionally, progesterone works to block muscular contraction of the uterus that would otherwise reject the egg.


Once the fertilized egg is implanted, the uterus develops a placenta which also produces progesterone throughout the pregnancy.


While progesterone is considered a female reproductive system hormone, men produce it too. Testicles produce progesterone in men. Why? Men need progesterone to produce testosterone. More precisely, progesterone supports spermiogenesis, sperm capacitation, and biosynthesis of testosterone in Leydig cells.


What causes high progesterone?

High progesterone is usually observed before menstruation and pregnancy. That being said, high progesterone can also occur due to other factors including cysts on ovaries and ovarian cancer.


High progesterone could be a sign of molar pregnancy, a rare complication wherein abnormal growth of cells in the placenta. In this pregnancy, the tissue inside the uterus forms into a mass or tumor. The only precise way to determine whether you have high progesterone and the causes behind it is to see the doctor and do a progesterone test.


What are the symptoms of high progesterone?

Symptoms of elevated progesterone levels can be tricky to identify since it’s easy to think you have PMS. Keep in mind in times of higher progesterone the body prepares itself for fertilization. The most common signs and symptoms of very high progesterone levels include:


  • Breast tenderness

  • Breast swelling

  • Weight gain

  • Low libido

  • Depression

  • Fatigue

  • Bloating

  • Anxiety and/or agitation


How does high progesterone affect the thyroid?

The relationship between progesterone and thyroid is poorly explored and further studies are necessary to learn more about it. Current evidence, however, shows the levels of progesterone can have an impact on the thyroid.


For example, one study found progesterone can upregulate thyroid cells. Scientists explained as progesterone elevated the expression of genes that play a role in the growth of thyroid cells and their differentiated function, its impact on this gland may be protective. In fact, a different study observed a free T4 increase in subjects who received progesterone and a tendency toward lower levels of TSH during the treatment with progesterone. High progesterone levels could amplify these effects and further elevate free T4 while lowering TSH. However, this theory would require a more thorough scientific investigation.


Although some evidence on the relationship between progesterone and thyroid exists, a lot more is necessary to elucidate all the mechanisms involved. It’s not just that progesterone influences the thyroid, vice versa also happens. The relationship between thyroid and progesterone is reciprocal. Adequate amounts of thyroid hormones are necessary for the production of progesterone in the ovaries. Plus, progesterone can increase the levels of thyroid hormone in the blood, as mentioned above. Additionally, progesterone can lower the levels of a protein that carries thyroid hormones in the blood meaning more hormone is free and gets into the cells.


Progesterone affects thyroid treatment

The effects of progesterone on the thyroid are different than those of estrogen, which is more invasive in this aspect. You see, progesterone lowers thyroid-binding globulin (TBG) and increases the activity of thyroid hormones when adequate levels are present.


Thyroid-binding globulin is defined as a globulin protein that carries hormones used or made by this butterfly-shaped gland. Why is this important? Well, increased TBG levels may elevate T3 and T4 without increasing the activity of these hormones in your body. Higher TBG levels could be due to several reasons including pregnancy, liver disease, and hypothyroidism.


For that reason, progesterone could aid the management of hypothyroidism by helping the body use available thyroid hormones more effectively. The body needs adequate levels of thyroid hormones for various functions including metabolism. Keep in mind further studies are necessary to shed more light on all mechanisms through which progesterone could influence the thyroid and management of problems affecting this important gland in your body.


A growing body of evidence confirms progesterone exhibits anti-inflammatory effects by acting on pro-inflammatory cytokines. This is particularly important if we bear in mind inflammation of a thyroid gland (thyroiditis) is a common problem that accounts for approximately 20% of all thyroid diseases. Thyroiditis can be acute, subacute, and chronic.


Moreover, inflammation can cause oxidative stress and affect the function of the thyroid thus causing non-thyroidal illness syndrome or depression of the pituitary-thyroid axis. It is also worth mentioning thyroid inflammation can lead to hypothyroidism and may interfere with the conversion of T4 hormone into T3. Additionally, inflammation can elevate reverse T3 (rT3), which is generally released when a person is ill, and may also inhibit the function of the T3 hormone.


Studies also reveal inflammation promotes the development of thyroid nodules indirectly by inhibiting the synthesis of thyroid hormones, which increases the concentration of TSH. Therefore, higher progesterone could exhibit anti-inflammatory effects thereby improving the management of thyroid problems linked to inflammation. That being said, the effects of excessively high progesterone may not be as beneficial and, at this point, no studies focused on that subject.


Progesterone acts on estrogen

Both estrogen and progesterone are important hormones for women’s sexual and reproductive health. When we’re discussing the impact of progesterone on the thyroid it’s also useful to address the relationship between estrogen and progesterone too. You see, progesterone reduces the response of target organs to estrogen by lowering the number of receptors the specific organ has for estrogen hormone. Also, while estrogen reduces bone breakdown rate, progesterone stimulates bone osteoblasts.


As mentioned above, progesterone decreases TBG and increases thyroid hormone activity. Thyroid hormones are necessary for metabolism and they also use the fat stored under influence of estrogen for energy. You also need progesterone for body composition.


Without progesterone, your body would get in the state of estrogen dominance. In a nutshell, estrogen dominance is a metabolic state where the body has insufficient levels of progesterone and high estrogen. Levels of estrogen can be normal, but you can still have estrogen dominance if progesterone is insufficient.


Estrogen dominance manifests itself through an array of symptoms including:


  • Polycystic ovaries

  • Weight gain

  • Brain fog

  • Fatigue

  • Headache

  • Insomnia

  • Infertility

  • Severe PMS

  • Mood swings

  • Slow metabolism

  • Irregular period

  • Water retention


Estrogen dominance affects thyroid health by inhibiting the conversion of T4 to T3. As a result, you have low T3 hormone levels meaning even though there is no specific problem with the gland itself, you may experience symptoms of hypothyroidism. If you take a closer look at the symptoms listed above, you will notice many of them are similar to those of hypothyroidism e.g. weight gain, fatigue, brain fog, and slow metabolism. Estrogen dominance can also contribute to Hashimoto’s thyroiditis, an autoimmune condition and the most common cause of hypothyroidism.




Estrogen can suppress thyroid hormone and increase the body’s need for TSH. Additionally, estrogen can also elevate TBG levels, but when thyroid hormones are attached to this protein they are inactive. This means the cells can’t use those hormones to fuel your body and regulate metabolism. The effects of estrogen dominance go beyond impaired utilization of thyroid hormone and extend to the immune system. Men and women with hypothyroidism find it more difficult to get rid of estrogen. Why? The liver is in charge of breaking down estrogen, but conditions involving an underactive thyroid gland slow down the function of your liver too. When left unmanaged, estrogen dominance can lead to Hashimoto’s thyroiditis primarily because your immune system releases TPO antibodies and TG antibodies.


Since high estrogen can have a negative influence on the thyroid gland and its hormones, progesterone is crucial. Progesterone can downplay these effects and prevent the inactivation of thyroid hormones. That being said, hormones do their best “work” when present in normal or healthy amounts. Excessive concentration of different hormones may not be the best idea as they also throw the body out of its equilibrium.

How to balance progesterone levels?

Every hormone has its roles and functions, which are impaired in the states of deficiency or excessive concentration. Progesterone is not the exception. Noticing high progesterone may not be that easy since symptoms are not specific to this condition. This is why it’s important to see the doctor regularly, report all symptoms you experience and do a progesterone test should the doctor recommend it. The best way to balance progesterone levels is to adhere to the doctor’s recommendations, but some lifestyle adjustments can help you out. These include:


  • Consume more fiber – proper digestion and good gut health require fiber intake. Reasons to consume fiber are numerous and progesterone balance is one of them. What many people don’t know is that fiber intake may reduce levels of progesterone. Another reason to eat more fiber is weight loss or its management. Keep in mind that some thyroid problems such as hypothyroidism can cause weight gain. While you should consume enough fiber to obtain health benefits from it, you should not go overboard as it could impair absorption of your thyroid hormone medication. Generally speaking, women need about 25g of fiber a day, and men need 38g


  • Stress management – studies show progesterone levels can increase in times of stress. The consequences of unmanaged stress are numerous. It can further slow down metabolism and contribute to weight gain. By managing stress, you can bring progesterone to normal and also support thyroid health at the same time. Stress management is highly individual, there are no rules here. You should adopt a strategy that works best for you. For most people stress management involves regular exercise, a healthy diet, and some relaxing activity such as a good book, writing, or meditation


  • Regular exercise – evidence confirms exercise can lower estrogen and progesterone levels. Exercise can also aid the management of symptoms caused by thyroid problems. For instance, regular physical activity may accelerate the metabolic rate and support weight loss. Additionally, exercise improves mood, helps you sleep better, and it happens to be a wonderful stress management strategy. For all these reasons it is important for men and women with thyroid problems to exercise regularly. It’s also useful to mention exercise supports the balance of other hormones in the body including testosterone


  • Quit smoking – adrenocortical secretion by smoking can increase progesterone levels in smokers. As an unhealthy habit, smoking can worsen symptoms of thyroid disease such as hypothyroidism, accelerate the progression of the disease, and make its treatment less effective. Even if you are a long-time smoker, you can still ditch this unhealthy habit successfully. All you need is a well-structured plan and support from loved ones


  • Get more vitamin D – sunshine vitamin may reduce progesterone levels. Low vitamin D levels are associated with autoimmune thyroid diseases such as Hashimoto’s and Graves’ disease. If you can’t obtain enough vitamin D through diet, you may want to consider taking supplements


Hormonal balance is vital for our health and the proper function of the thyroid. The functionality of the butterfly-shaped gland largely depends on other hormones too. The role of progesterone could be protective in some circumstances, but a lot more research is necessary to elucidate the impact of excessive amounts of progesterone on the thyroid. You may want to consult your doctor and do a progesterone test to determine whether you have a high, low, or normal concentration of this hormone.



















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