What Causes PCOS? and How Will It Affect My Body?

A review of the possible reasons behind why you may have polycystic ovary syndrome (PCOS), and what symptoms might indicate a diagnosis of this condition.

Written by Sari Harrar
Reviewed by Priyathama Vellanki MD

Doctors have been taking note of Polycystic Ovary Syndrome (PCOS) symptoms in their female patients since at least the 1700s.1 Yet, here we are hundreds of years later with the underlying reason for this common women’s health syndrome remaining a mystery.2,3

Experts in women’s health and endocrinology have important new clues that expand our understanding of what’s behind this condition—and that may offer new directions for better treatment and improved care.4-7

Polycystic Ovary Syndrome Causes: Genetics

Genes Trigger a Hormone Cascade

The reason you may develop PCOS is, at least in part, determined by your genes. You can inherit the risk for PCOS.6 In a study conducted at the University of Alabama at Birmingham, the researchers found that 24% of women with polycystic ovary syndrome had a mother with PCOS and 32% of the women had a sister with the condition.6

Family members of women who have PCOS are also at higher risk for developing the same metabolic abnormalities. However, there’s no single PCOS gene. A wide variety of genes and mechanisms seem to be at work, which may explain why PCOS has a wide range of symptoms and develops at different ages for women. Several genetic studies in PCOS implicate genes that affect hormone levels and insulin resistance.6,7

Most women with polycystic ovary syndrome can expect to gain excess weight. Obesity and overweight status contribute to insulin resistance. While obesity exacerbates insulin resistance, even lean women with PCOS have insulin resistance. Researchers have shown that women with PCOS regardless of their weight (overweight and lean) will experience insulin resistance as compared to women of the same age and weight who do not have PCOS.This is notable because it suggests that the excess weight—often a key factor in insulin resistance in women (and men) without PCOS—isn’t the only factor causing insulin problems in people who have PCOS.

Insulin Resistance Leads to High Testosterone  

In women with PCOS, insulin resistance is often a red flag that you may have prediabetes and are at risk for diabetes—as well as for those without polycystic ovary syndrome.7,9 Insulin resistance means your body is less able to send enough glucose to the cells needing fuel throughout your body. When this happens, the pancreas produces more insulin to help keep glucose levels even. The extra insulin may have several negative effects including shutting down your ovaries and leading to higher than normal levels of male hormones, called androgens, including testosterone.

For women with PCOS, higher levels of androgens are likely to interfere with or even halt normal ovulation, in part, by altering levels of luteinizing hormone and gonadotropin-releasing hormone, both of which are involved in the development and release of an egg at the midpoint of a woman’s menstrual cycle. 10 

When you aren’t ovulating regularly, it will cause irregular periods or amenorrhea (the absence of menstrual cycles), infertility, and development of ovarian cysts for many but not all women, with PCOS. In addition, if you have PCOS, having excessive androgens can also lead to severe acne and the excess growth of hair (hirsutism) on your face, neck, chest, arms, and legs.3,9,10 Meanwhile, insulin resistance can produce skin changes (like skin tags and darkened areas) and contributes to undesirable and stubborn weight gain, which makes other PCOS symptoms worse.3

Hormone Imbalances Impose Negative Effects on Your Whole Body

Hormones affect tissues throughout your body and can increase your odds of health conditions that you might not readily associate with more familiar PCOS issues such as infertility and menstrual problems.10 The hormonal imbalances behind PCOS put women at higher-than-normal risk for a wide range of well beyond the reproductive system.    

Are Ovarian Cysts and Pelvic Pain Common Symptoms?

If you have PCOS, multiple bubble-like cysts may form on the surface of one or both of your ovaries as eggs partially mature but are not released. These eggs remain in their follicles, which swell but don’t open. A woman with PCOS may have 25 or more cysts on a single ovary. These cysts are usually silent, meaning there isn’t usually any noticeable symptoms, although some women do report pelvic pain.12

It’s important to know that not all women with PCOS have ovarian cysts or that having ovarian cysts is not an automatic sign of having PCOS. It’s very unlikely that you will feel them.12 Rather, multiple cysts and large cysts, are most often found by ultrasound when your doctor is trying to determine if you have PCOS.

Even though this metabolic (hormone-related) condition is called polycystic ovary Syndrome, many women with PCOS do not have ovarian cysts. You don’t have to have any cysts on your ovaries to be diagnosed with PCOS. 

That is why “the National Institutes of Health has recommended changing the name of this syndrome to one that more accurately reflect the range of metabolic, psychological, and reproductive complications typically experienced by women with PCOS,” Scott Isaacs, MD, an endocrinologist with Atlanta Endocrine Associates, and adjunct instructor of medicine at Emory University School of Medicine in Atlanta, Georgia, told EndocrineWeb.

Risks Associated with Reproductive Cancers: Ovarian, Endometrial, Breast

Irregular menstrual periods cause the lining of the uterus, the endometrium, to continually grow and thicken – rather than shedding every 28 days or so as happens with regular menstrual cycles. This buildup increases the risk for endometrial hyperplasia in which cells in the endometrial lining bunch together and begin taking on abnormal shapes. It also nearly triples risk for endometrial cancer for women with polycystic ovary syndrome,13 according to a University College London review of 11 well-designed studies involving 919 women with PCOS and more than 72,000 women without PCOS.

This study,13 published in the journal Human Reproduction Update, did not find an increased risk for breast cancer or ovarian cancer but others studies have found higher odds of these cancers occurring in women with PCOS. The researchers note that despite the elevated risk of endometrial cancer, women with PCOS should know that it’s still a rare form of cancer that affects only about 24 in 100,000 women each year in the US,14 according to the American Cancer Society.

A Closer Look at Common Symptoms of PCOS

Now that you have a sense of the dizzying array of symptoms that might lead to a diagnosis of PCOS, it's important to understand the questions that your doctor might ask and the types of tests she or he will want to do in trying to determine what is responsible for your symptoms. An accurate diagnosis will assure you get the right type of care to help manage your symptoms and improve your risk for worrisome conditions like diabetes, heart disease, and more, which will be discussed in Part 3: Diagnosing PCOS: What Tests Should You Expect?



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2.    American College of Obstetricians and Gynecologists. Polycystic Ovary Syndrome. (PCOS): Frequently Asked Questions.” Available at: www.acog.org/Patients/FAQs/Polycystic-Ovary-Syndrome-PCOS. Accessed November 14, 2017.

3.    ACOG Committee on Practice Bulletins-Gynecology. ACOG Practice Bulletin No. 108: Polycystic ovary syndrome. Obstet Gynecol. 2009;114(4):936-949.

4.    Goodman NF, Cobin RH, Futterweit W, et al.  American Association of Clinical Endocrinologist, American College of Endocrinology and Androgen Excess and PCOS Society Disease state clinical review: Guide to the best practices in the evaluation and treatment of polycystic ovary syndrome-Part 1. Endocr Pract. 2015;21(11):1291-1300.

5.    Marshall JC, Dunaif A. All Women With PCOS Should Be Treated For Insulin Resistance. Fertil Steril. 2012;97(1):18–22.

6.    Kahsar-Miller MD et al. Prevalence of polycystic ovary syndrome (PCOS) in first-degree relatives of patients with PCOS.” Fertil Steril. 2000;75(1):53-58.

7.      Goodarzi M, et al. Polycystic ovary syndrome: Etiology, pathogenesis and diagnosis.”  Nat Rev Endocrinol, 2011.;7(4):219–231. 

8.      Kataoka J, et al. Weight Management Interventions in Women with and without PCOS: A Systematic Review. Nutrients. 2017;9:996.

9.      Barbieri RL, et al. Patient education: Polycystic ovary syndrome. Beyond the Basics. UptoDate. Available at: www.uptodate.com/contents/polycystic-ovary-syndrome-pcos-beyond-the-basics

10.  Office of Women’s Health, US Department of Health and Human Services. Menstrual cycle. Available  at:www.womenshealth.gov/menstrual-cycle.

11.  Sanchez Melo A, et al. Treatment of infertility in women with polycystic ovary syndrome: approach to clinical practice. Clinics (Sao Paulo). 2015;70(11):765–769.

12.  Office of Women’s Health. US Department of Health and Human Services. Ovarian cysts. Available at: www.womenshealth.gov/a-z-topics/ovarian-cysts.

13.  Barry JA, et al. Risk of endometrial, ovarian, and breast cancer in women with polycystic ovary syndrome: A systemic review and meta-analysis. Human Reproduction Update. 2014;20(5):748–758.   

14.  American Cancer Society Cancer Statistics Center, 2017 Estimates. Available at: https://cancerstatisticscenter.cancer.org/#!/

15.  Napolitano M. Insulin Resistance and Skin Diseases. Scientific World Journal. 2015; 479354. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4419263/.

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17.  Fogel RB, et al. Increased prevalence of obstructive sleep apnea syndrome in obese women with polycystic ovary syndrome.  J Clin Endocrinol Metab. 2001;86(3):1175–1180

18.       Vgontzas AN, et al. Polycystic ovary syndrome is associated with obstructive sleep apnea and daytime sleepiness: role of insulin resistance.  J Clin Endocrinol Metab. 2001; 86(2):517-520.

19.       Borghi L, et al. Psychological distress, anger and quality of life in polycystic ovary syndrome: associations with biochemical, phenotypical andsocio-demographic factors.” J Psychosom Obstet Gynaecol. 2017;6:1-10.

20.       Balikci A, et al Depression, Anxiety, and Anger in Patients with Polycystic Ovary Syndrome. Noro Psikiyatr Ars. 2014;51(4):328-333. 

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Polycystic Ovary Syndrome (PCOS): How Is It Diagnosed?