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

A review of the causes of PCOS and a detailed look at PCOS symptoms

Polycystic ovary syndrome occurs partly from a genetic link and also due to hormone imbalances.Your genes hold one clue as to why you may have polycystic ovary syndrome (PCOS).

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.    

  • Irregular menstrual cycles: Most women with PCOS have unpredictable menstrual cycles with infrequent periods (often more than 35 days apart) or no periods at all (amenorrhea). The reason for you irregular ovulation or no menstruation is a direct effect of hormone imbalances. Your periods may be light because you’re not ovulating or extremely heavy because the lining of your uterus, called the endometrium, continues to thicken when the monthly cycle doesn’t happen. Since this lining is shed during a menstrual period, there is more to shed when you do menstruate. Women with PCOS typically have fewer than six to eight menstrual periods in a year (the norm is about 10 to 17 periods per year.)8 About 10-15% of women with polycystic ovary syndrome have slightly longer cycles, lasting 32-36 days.9,10
  • Infertility: With PCOS, hormonal imbalances interfere with normal ovulation. When your ovaries do not release an egg, you can’t conceive. Polycystic ovary syndrome is the leading cause of infertility in women,3 according to the American College of Obstetricians and Gynecologists. Infertility affects up to 80% of women with PCOS.  There is good news for women who want to become pregnant: Strategies including lifestyle changes, ovulation-inducing medications, surgery and other fertility treatments mean most women with PCOS will be able to become pregnant.11

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

  • Weight gain: Approximately 80% of women with PCOS gain weight.8 When the body stores more fat than is healthy – especially in your midsection (abdominal fat), it further raises your risk for serious chronic diseases like diabetes, cardiovascular disease, and even endometrial cancer.While weight gain doesn’t cause PCOS, it can make it harder to manage your weight, but it’s helpful to know that by losing just 2-10% of your excess body fat (which is often just 5-10 lbs for many women), you can improve many PCOS-related symptoms.
  • Excessive hair growth or hair loss: About 70% of women with PCOS develop so-called “male-pattern” hair growth on the upper lip, chin, neck, sides of the face, abdomen, lower back, upper arms, and inner thighs.15  Some women also have “male-pattern” hair thinning of the scalp and top of the head. The cause of these hair changes is attributed to high androgen levels that stimulate hair follicles.
  • Adult acne: High levels of male hormones that occur in women with PCOS may also cause severe acne on your face, chest, and back – particularly in women who are past their teen years.15 One clue to the cause: These break-outs and clogged pores may not clear up with conventional acne treatments from the drugstore or from your family doctor or dermatologist.
  • Other skin changes: Insulin resistance and high insulin levels can lead to the development of patches of thick, velvety, skin that’s darker than your normal skin tone. Called Acanthosis nigricans, it often shows up in the skin creases around your neck, groin, and under your breasts.15  You may also have skin tags (very small skin growths) in your armpits or on your neck, which may also be a sign of insulin resistance.15
  • Type 2 diabetes: The insulin resistance that develops in women with PCOS is a potent risk factor for type 2 diabetes (T2D), at least in part, because it occurs at a younger age in women with PCOS than those who do not have this metabolic condition.16 In fact, the risk for T2D is four times higher in women who have polycystic ovary syndrome.16And, at least half of all women with PCOS develop prediabetes or diabetes before reaching 40 years old.16
  •  Diabetes can develop swiftly with 5-15% of women with PCOS moving from normal blood sugar levels to developing diabetes within three years of a PCOS diagnosis,16 according to researchers at the University of Athens. Diabetes brings with it the lifelong need to track blood sugar, watch the types and amounts of carbohydrates you eat, keep physically active, and will usually require anti-diabetes medications. Diabetes also raises your risk of developing systemic nerve damage (diabetic neuropathy), vision changes, kidney problems, and, as you’ll read next, cardiovascular disease.
  • Cardiovascular disease: Women with PCOS are at higher risk for high blood pressure, stiff and clogged arteries, high levels of heart-damaging LDL cholesterol and low levels of protective HDL cholesterol that occurs with poorly managed diabetes.3 Women with PCOS also are at higher-than-average risk for heart disease, heart attacks, heart failure, and stroke. In one study of women younger than age 60 who had imaging scans of their arteries, those with PCOS had more areas of significant and dangerous narrowing of their arteries due to atherosclerosis (a buildup of fatty plaque in artery walls) than women without polycystic ovary syndrome.7
  • Obstructive sleep apnea: Brief but repeated pauses in breathing during sleep, caused by relaxed muscles that let your airways close for a few seconds, are more common in women with PCOS,17 as reported by researchers from Brigham and Women's Hospital and Harvard Medical School in a widely-cited study in the Journal of Clinical Endocrinology and Metabolism. Sleep apnea can contribute to dangerous daytime fatigue, memory loss, mood swings, and weight gain associated with diabetes, and heart disease. Women with PCOS are 30 times more likely than women without polycystic ovary syndrome to have disordered breathing during sleep (OSA) as well as heavy snoring that commonly occurs in people who have sleep apnea, and are nine times more likely to feel fatigued during the day from poor sleep, according to a Penn State University study in the same journal.18
  • Mood disorders: Anxiety, distress, depression and eating disorders are more common in women with PCOS.19 Experts don’t agree on why – some suspect excess androgens and other hormone imbalances are the cause of mood changes, while others say distress is a common response to living with concerns like infertility, undesirable weight gain, and excess hair growth. 19,20

Take our two-minute PCOS symptoms quiz to get an assessment of the likelihood that you are suffering from 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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Polycystic Ovary Syndrome (PCOS): How Is It Diagnosed?