By Megan N. Coughlin
Editor’s Note: This week, we feature an interesting review of research published in 2023 by Li et al [1] on the association between metabolic syndrome and endometriosis. It was summarized by Megan Coughlin while on the FACTS elective, Fertility Awareness-Based Methods for Family Planning and Women’s Health. The study findings highlight the need to monitor markers of metabolic syndrome in women with endometriosis, including lipid levels and, specifically, triglycerides. Other surprising study results point to the need for more research in this area given the high prevalence and diagnostic challenges associated with endometriosis.
Introduction
Endometriosis is diagnosed in 5 to 10% of women and may cause painful periods and intercourse, chronic pelvic pain, and infertility. Metabolic syndrome is associated with increased risk of diabetes and cardiovascular disease and is a contributing factor to mortality worldwide. Some studies now link endometriosis and metabolic disease.
Endometriosis is an estrogen-dependent inflammatory disease, and the evidence supports that inflammation affects lipid metabolism and leads to elevated LDL cholesterol and blood pressure. Another study by Farland et al [2] found that endometriosis was associated with higher risk of type 2 diabetes. Prior studies have also found an association between endometriosis and waist circumference, hypercholesterolemia, and hypertension. The study by Li et al [1] summarized below sought to explore the association between endometriosis and metabolic syndrome as well as endometriosis and individual indicators for metabolic syndrome.
“Endometriosis is an estrogen-dependent inflammatory disease, and the evidence supports that inflammation affects lipid metabolism and leads to elevated LDL cholesterol and blood pressure.”
Methods
This cross-sectional study selected data collected by the National Health and Nutrition Examination Survey from 1999 to 2006. The study included 5,557 women in the endometriosis questionnaire, and 2,389 of them had data on the assessment of metabolic syndrome and were thus analyzed in the study. Of the 2,389 included in the analysis, 2,212 (93%) reported not having been told by their doctor that they had endometriosis, while 7% (177) reported they were told by their doctor they had endometriosis.
The metabolic syndrome factors analyzed were waist circumference, systolic and diastolic BP, triglycerides, low HDL, and fasting plasma glucose. Additional individual factors included a history of hysterectomy/oophorectomy, pregnancy status, use of female hormones, and use of medications for diabetes, dyslipidemia, and/or hypertension.
Results
Multiple factors were identified as confounders, including age, race, education level, family poverty-income ratio (PIR), smoking, age at menarche, gravidity, menopause, hysterectomy/oophorectomy, use of female hormones, and use of medication for dyslipidemia. In the unadjusted sample, the odds of having metabolic syndrome and endometriosis were 1.55 (95% CI: 1.06-2.25). After adjusting for age, race, education level, family PIR, smoking, age at menarche, gravidity, menopause, female hormone use, and dyslipidemia drugs, the odds were also 1.55 (95% CI: 1.01-2.35). When adjusted for hysterectomy/oophorectomy, the association between endometriosis and metabolic syndrome was no longer statistically significant.
“The odds of having metabolic syndrome and endometriosis were 1.55 (95% CI: 1.06-2.25) [even] after adjusting for age, race, education level, family poverty-income ratio, smoking, age at menarche, gravidity, menopause, female hormone use, and dyslipidemia drugs.”
A statistically significant association was found between endometriosis and triglyceride level, with similar results seen after adjusting for women with a history of a hysterectomy or oophorectomy.
Discussion
The study by Li et al [1] revealed a significant association between metabolic syndrome and endometriosis, with higher odds for patients with endometriosis to also have metabolic syndrome compared to women without endometriosis. While there was no statistically significant relationship between endometriosis and metabolic syndrome in women with a history of hysterectomy or oophorectomy, women with endometriosis were found to have elevated triglycerides regardless of their hysterectomy or oophorectomy status. These findings were of particular interest.
Many women with endometriosis undergo endometriosis-removing surgeries to alleviate their pain, with some undergoing hysterectomy or oophorectomy as part of the management. Studies show that hysterectomy/oophorectomy may increase the risk of metabolism-related disease; thus, further research is needed on surgical treatments for endometriosis and risk of metabolic disease.
Determining whether surgery for endometriosis could potentially reduce risk factors for metabolic disease may guide future surgical decision making. Whether a patient has had surgery for endometriosis, hysterectomy, or oophorectomy, monitoring for metabolic syndrome should continue even after symptoms improve until the relationship between metabolic syndrome and endometriosis is better understood.
“Determining whether surgery for endometriosis could potentially reduce risk factors for metabolic disease may guide future surgical decision making.”
Regardless of surgical status, it is also important to consider the relationship between elevated triglycerides and endometriosis. Prior studies have shown that women with endometriosis had greater arterial stiffness than controls. With this in mind, clinicians should be cautioned to monitor lipid status closely in women with endometriosis.
Another avenue of interest would be the intersection between polycystic ovary syndrome (PCOS), endometriosis, and metabolic syndrome. PCOS is a metabolic condition associated with insulin resistance, and estimates suggest around 50% of women with PCOS have concurrent endometriosis. It is not possible to elucidate whether the elevated odds of metabolic syndrome found by Li et al [1] in patients with endometriosis included patients who also had PCOS. It would be worth exploring this association further to determine if PCOS is a causal factor.
This study sheds some light on endometriosis and metabolic syndrome, but it is not without its flaws. As noted by the authors, the National Health and Nutrition Examination Survey consists of self-reported data from the United States. As self-reported data leaves room for bias, a broader sample size beyond the U.S. would provide a better estimate of the odds of metabolic syndrome on a global scale. The cross-sectional study design can show correlation but not causation. The sample size of 177 patients with endometriosis is small, so further studies with larger sample sizes would be welcome.
Editor’s Note: Follow the links below to learn more about the management of endometriosis from a restorative approach focused on treating the root cause and restoring overall wellbeing.
- Endometriosis Diagnosis, Treatment, and the Role of FABMs: A Review
- Endometriosis in Adolescents: A Review of Research
References
[1] Li, B., Zhang, Y., Zhang, L., & Zhang, L. (2023). Association between endometriosis and metabolic syndrome: a cross-sectional study based on the National Health and Nutrition Examination Survey data. Gynecological Endocrinology, 39 (1). https://doi.org/10.1080/09513590.2023.2254844
[2] Farland LV, Degnan WJ, Harris HR, Tobias DK, Missmer SA. (2021) A prospective study of endometriosis and risk of type 2 diabetes. Diabetologia. doi: 10.1007/s00125-020-05347-6.
ABOUT THE AUTHOR
Megan N. Coughlin is a fourth-year medical student at New York Institute of Technology College of Osteopathic Medicine in Jonesboro, Arkansas. She completed her undergraduate education at the University of Central Florida in Orlando, FL and earned a master’s degree at the University of South Florida in Tampa, FL. She plans to pursue residency in obstetrics and gynecology and is interested in medical education and advocacy. She enrolled in the FACTS elective to gain a better understanding of family planning methods and their utilization in clinics across the country.
