Irregular periods and endometrial cancer

Endometrial cancer is a prevalent form of cancer that affects the lining of the uterus. While it is one of the most common gynecological cancers, there is a growing concern about the impact of irregular periods on the risk of developing this disease. 

This article aims to shed light on the relationship between irregular periods, specifically cycle abnormalities that are caused by anovulation and high levels of estrogen, and endometrial cancer risk. Read on to learn: 

• What is endometrial cancer?
• What is an irregular period?
• How do irregular periods increase risk for endometrial cancer? 
• How does birth control play a role in reducing risk for endometrial cancer?

Endometrial cancer overview 

Endometrial cancer refers to the abnormal growth of cells in the lining of the uterus, known as the endometrium. It is the most common type of uterine cancer and primarily affects postmenopausal individuals. 

However, it can also occur in younger people, especially those with certain risk factors. Endometrial cancer is typically detected early, and the prognosis is generally favorable with a five-year survival rate of about 80-85% for localized disease. However, late-stage diagnosis can significantly impact survival rates (1).

What even is an irregular period?

An irregular period, also known as irregular menstrual bleeding or irregular menstruation, refers to a menstrual cycle that deviates from the typical pattern. 

The below are signs that you may be experiencing an irregular period:

• Long or short cycle length: Menstrual cycles (i.e. the amount of time between day 1 of your period and the day before your next period) that are shorter than 24 days or longer than 35 days* fall outside of “normal” bounds. 
• Heavy or light menstrual flow: Irregular periods can involve variations in the amount of menstrual flow. This might include heavy bleeding or lighter bleeding. A “normal” period typically produces 30 to 60 milliliters of blood, or 2 to 4 tablespoons-worth.
• Long or short duration of bleeding during period: The length of menstrual bleeding can differ from the usual pattern but 2-7 days is said to be “normal.”
• Intermittent bleeding: Irregular periods may include episodes of intermittent bleeding or spotting between periods.
• Skipped or missed periods: People with irregular periods might have cycles where periods are skipped entirely or occur only several times per year.

Irregular periods can be caused by various factors, including hormonal imbalances, stress, changes in weight, certain medical conditions (such as polycystic ovary syndrome, thyroid disorders, and functional hypothalamic amenorrhea), medications, and certain lifestyle factors. It's important to consult with a healthcare professional if you experience persistent irregular periods or if your menstrual pattern changes significantly, as they can help determine the underlying cause and provide appropriate guidance and treatment options.

Want to learn more about what  “normal” vs. irregular periods looks like? Check out this article.

How irregular periods can increase endometrial cancer risk

Irregular periods - both short and long cycles - have been linked to an increased risk of endometrial cancer. This is largely because irregular periods occur alongside heightened levels of the hormone estrogen. 

Understanding estrogen dominance

A “regular” menstrual cycle involves a delicate balance between estrogen and progesterone hormones. 

Each month, estrogen rises in advance of ovulation in addition to other hormones such as luteinizing hormone (LH) and follicle stimulating hormone (FSH). Once ovulation occurs, progesterone is produced by the corpus luteum, or a temporary structure that forms in our ovary after ovulation and has the responsibility of producing progesterone for the first part of a pregnancy. 

If pregnancy occurs in any given cycle, the placenta ultimately takes over progesterone production - but if no pregnancy occurs, the corpus luteum disintegrates, subsequently halting progesterone production and triggering our period.  

When this balance is disrupted due to excess estrogen production or circulation, progesterone deficiency, or both, a state known as estrogen dominance, or excessive estrogen relative to progesterone, can occur. Over time, estrogen dominance can lead to an overgrowth of the endometrial lining and the development of endometrial hyperplasia, a precancerous condition that can progress to endometrial cancer if left untreated (2).

Estrogen dominance that results from irregular or absent ovulation 

Estrogen dominance often - but not always - occurs if you are not ovulating frequently or if you have “weak” ovulation. As discussed above, progesterone production depends on successful ovulation; and if successful ovulation is not occurring, a progesterone deficiency will follow.

This can result in prolonged exposure of the endometrium (i.e., lining of your uterus) to estrogen without the balancing effect of progesterone. This estrogen dominance can cause excessive growth of the endometrium, increasing the risk of endometrial cancer.

Polycystic ovary syndrome (PCOS) is a common hormone imbalance that is often characterized by irregular or absent ovulation and can greatly increase risk for endometrial cancer. 

Below are ways that you can assess whether you have ovulated or not in any given menstrual cycle:

• Basal body temperature (BBT) tracking 
• PdG testing with a test like Proov’s 
• Lab test of progesterone on days 19-21 of your cycle (or roughly 1 week after suspected ovulation) 

Estrogen dominance that results from overproduction of estrogen or improper estrogen metabolism 

However, estrogen dominance can also occur for people who ovulate regularly! 

Herein enters endometrial cancer risk factors such as estrogen overproduction and improper metabolism (3):

• If your body is overproducing estrogen, estrogen dominance can occur. Having a high percentage of body fat can increase this risk. There are also diseases such as aromatase excess syndrome that can cause this. 
• If your body is not metabolizing estrogen efficiently, estrogen dominance can also occur. Estrogens are eliminated from the body by metabolic conversion that are excreted in our urine and feces. If your liver is not working efficiently or if you struggle with constipation due to factors like poor gut health, this can result in high levels of estrogen continuing to circulate in your body and building up to unhealthy levels over time (4).

Symptoms that you may be experiencing this kind of estrogen dominance include: 

• Menstrual cycles that arrive on a regular or semi-regular basis
• Significant pain and cramping before and during your period 
• Heavy bleeding and/or bleeding that lasts for longer than 7 days 
• Extreme PMS symptoms before your period such as swollen or tender breasts, bloating, pelvic pain, and shifts in mood

Birth control's impact on endometrial cancer risk

Even though some hormonal contraceptives may cause you to not have a “period” (pro tip: we are doing air quotes here because what is oftentimes call a “period” on birth control is actually just a withdrawal bleed), they still lower the risk of endometrial cancer. Given what we just reviewed above, this may seem counterintuitive! .

Birth control pills contain synthetic versions of estrogen and progesterone (combination methods) or progesterone alone (progestin-only methods or the mini pill). By taking these hormones, birth control regulates the menstrual cycle and prevents the excessive growth of the endometrium. This is why birth control is often prescribed to people with irregular periods or conditions like PCOS.

Thus, the consistent use of hormonal contraceptives can help maintain a more regular hormonal environment and prevent the overgrowth of the endometrium. 

It's important to note that while birth control can lower the risk of endometrial cancer, it may slightly increase the risk of other types of cancer, such as breast and cervical cancer. However, the overall benefits of birth control in preventing unintended pregnancies and managing certain medical conditions often outweigh the potential risks. It's recommended to discuss the specific risks and benefits of birth control methods with a healthcare provider.

Conclusion

It is important to note that while irregular periods can be a potential risk factor for endometrial cancer, not all people with irregular periods will develop the disease. Regular check-ups, awareness of associated conditions, and early detection through screening can help mitigate the risk and ensure appropriate management if any abnormalities are detected.

If you have concerns about your menstrual cycle or risk of endometrial cancer, it is recommended to consult with your doctor for more personalized guidance and support.

Sources

1. American Cancer Society. (2021). Key statistics for endometrial cancer. Retrieved from https://www.cancer.org/cancer/endometrial-cancer/about/key-statistics.html
2. Australian Government Department of Health. (2020). Endometrial cancer (uterine cancer). Retrieved from https://www.healthdirect.gov.au/endometrial-cancer-uterine-cancer. 
3. https://www.va.gov/WHOLEHEALTHLIBRARY/tools/estrogen-dominance.asp 
4. Tsuchiya Y, Nakajima M, Yokoi T. Cytochrome P450-mediated metabolism of estrogens and its regulation in human. Cancer Lett. 2005 Sep 28;227(2):115-24. doi: 10.1016/j.canlet.2004.10.007. Epub 2004 Nov 19. PMID: 16112414. https://pubmed.ncbi.nlm.nih.gov/16112414/. 

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