Women with PCOS are at a higher risk for a number of illnesses, including high blood pressure, diabetes, heart disease , and cancer of the uterus(endometrial cancer).Because of the menstrual and hormonal irregularities, infertility is common in women with PCOS. Because of the lack of ovulation, progesterone secretion in women with PCOS is diminished, leading to long-term unopposed estrogen stimulation of the uterine lining. This situation can lead to abnormal periods, breakthrough bleeding, or prolonged uterine bleeding in some women. Unopposed estrogen stimulation of the uterus is also a risk factor for the development of endometrial hyperplasia and cancer of the endometrium (uterine lining). However, medications can be given to induce regular periods and reduce the estrogenic stimulation of the endometrium (see below).Obesity is associated with PCOS. Obesity not only compounds the problem of insulin resistance and type 2 diabetes (see below), but also imparts cardiovascular risks. PCOS and obesity are associated with a higher risk of developing metabolic syndrome , a group of symptoms, including high blood pressure, that increase the chances of developing cardiovascular disease. It has also been shown that levels of C-reactive protein (CRP), a biochemical marker that can predict the risk of developing cardiovascular disease, are elevated in women with PCOS. Reducing the medical risks from PCOS-associated obesity is possible.The risk of developing prediabetes and type 2 diabetes is increased in women with PCOS, particularly if they have a family history of diabetes. Obesity and insulin resistance, both associated with PCOS, are significant risk factor for the development of type 2 diabetes. Several studies have shown that women with PCOS have abnormal levels of LDL ("bad") cholesterol and lowered levels of HDL ("good") cholesterol in the blood. Elevated levels of blood triglycerides have also been described in women with PCOS.Changes in skin pigmentation can also occur with PCOS. Acanthosis nigricans refers to the presence of velvety, brown to black pigmentation often seen on the neck, under the arms, or in the groin. This condition is associated with obesity and insulin resistance and occurs in some women with PCOS.