When ovulation does not occur regularly, the lining of the uterus (the endometrium) does not uniformly shed and regenerate as in a normal menstrual cycle. Instead the endometrium gets thicker and sheds unpredictably. As a result, not only the onset of menstrual bleeding is unpredictable, the bleeding is often heavy and/or prolonged. Prolonged heavy bleeding is not merely inconvenient. It can lead to chronic fatigue from iron deficient anemia. It is not uncommon for women with PCOS present with an excessive blood loss from an episode of heavy and prolonged bleeding that blood transfusion may be necessary.
There is an additional risk with irregular mense among women with PCOS. When the endometrium fails to shed properly and is chronically exposed to abnormal level of ovarian hormones, it can develop into an abnormality called endometrial hyperplasia and even endometrial cancer.
Hair growth and acne
The elevated level of male hormones, also known as ovarian androgen excess, from the ovary (and sometimes from the adrenal gland as well) causes male-pattern hair growth (hirsutism) on the upper lip, chin, neck, sideburn area, chest, upper or lower abdomen and inner thigh. The elevated level of male hormones leads to excessive oil production in the hair follicle of the skin and facilitates bacterial overgrowth leading to acne. Acne is a common skin disease in which the skin pores become blocked, causing pimples to develop.
Weight gain and obesity
About half of all women with PCOS have gradual weight gain leading to obesity. Some women with PCOS develop obesity at the time of puberty. It is unclear exactly how the abnormal levels of male sex hormones and insulin are linked to weight gain.
Insulin is a hormone produced by specialized cells (islets of langerhans beta cells) in the pancreas. Insulin regulates blood glucose levels. When blood glucose levels go up (for example: after a meal), these cells produce insulin to help the body to use glucose for energy. All types of insulin abnormalities are found to be more common among women with PCOS.
Insulin resistant and hyper-insulinemia
If glucose levels do not respond to normal levels of insulin, the pancreas produces more insulin. The condition where excess insulin is required to maintain normal glucose level is called insulin resistant. When the blood levels of insulin are elevated above normal, it is called hyper-insulinemia.
Glucose intolerance and pre-diabetes
When glucose levels are not completely controlled, even with the increased amounts of insulin, the condition is called glucose intolerance, also known as pre-diabetes.
Type 2 diabetes
If blood glucose levels continue to rise above certain defined values (the American Diabetic Association and the World Health Organization have slightly different diagnostic criteria) despite increased insulin levels, the condition is called type 2 diabetes.
It appears that PCOS adds an additional risk to develop all types of insulin abnormalities independent of body weight. Current research shows that insulin resistance and hyper-insulinemia are more common among both normal-weight and obese women with PCOS. As well the risk of developing type 2 diabetes is higher among women with PCOS compared with women without PCOS.
Since women with PCOS have irregular cycles or infrequent ovulation, it comes as no surprise that women with PCOS have difficult getting pregnant.