Obesity and metabolic abnormalities are recognized risk factors for the development of ischaemic heart disease (IHD) in the general population, and these are also recognized features of PCOS. The question is whether women with PCOS are at an increased risk of IHD, and whether this will occur at an earlier age than women with normal ovaries. The basis for the idea that women with PCOS are at greater risk for cardiovascular disease is that these women are more insulin resistant than weight-matched controls and that the metabolic disturbances associated with insulin resistance are known to increase cardiovascular risk in other populations. Insulin resistance is defined as a diminution in the biological responses to a given level of insulin. In the presence of an adequate pancreatic reserve, normal circulating glucose levels are maintained at higher serum insulin concentrations. In the general population cardiovascular risk factors include insulin resistance, obesity, glucose intolerance, hypertension, and dyslipidaemia.
There have been a large number of studies demonstrating the presence of insulin resistance and corresponding hyperinsulinaemia in both obese and non-obese women with PCOS . Obese women with PCOS have consistently been shown to be more insulin resistant than weight-matched controls. It appears that obesity and PCOS have an additive effect on the degree and severity of the insulin resistance and subsequent hyperinsulinaemia in this group of women. The insulin resistance causes compensatory hypersecretion of insulin, particularly in response to glucose, so euglycaemia is usually maintained at the expense of hyperinsulinaemia. Insulin resistance is restricted to the extra-splanchnic actions of insulin on glucose dispersal. The liver is not affected (hence the fall in SHBG and HDL), neither is the ovary (hence the menstrual problems and hypersecretion of androgens) nor the skin, hence the development of acanthosis nigricans. Women with PCOS who are oligomenorrhoeic are more likely to be insulin resistant than those with regular cycles - irrespective of their BMI, with intermenstrual interval correlating with the degree of insulin resistance .
Women with PCOS have a greater truncal abdominal fat distribution as demonstrated by a higher waist:hip ratio. The central distribution of fat is independent of BMI and associated with higher plasma insulin and triglyceride concentrations, and reduced HDL (high-density chole-strol) concentrations. From a practical point of view, if the measurement of waist circumference is greater than
88 cm, there will be excess visceral fat and an increased risk of metabolic problems.
Thus there is evidence that insulin resistance, central obesity and hyperandrogenaemia have an adverse effect on lipid metabolism, yet these are surrogate risk factors for cardiovascular disease. However, Pierpoint et al.  reported the mortality rate in 1028 women diagnosed as having PCOS between 1930 and 1979. All the women were older than 45 years and 770 women had been treated by wedge resection of the ovaries. Seven hundred and eighty-six women were traced; the mean age at diagnosis was 26.4 years and average duration of follow-up was 30 years. There were 59 deaths, of which 15 were from circulatory disease. Of these 15 deaths, 13 were from ischaemic heart disease. There were six deaths from diabetes as an underlying or contributory cause compared with the expected 1.7 deaths. The standard mortality rate both overall and for cardiovascular disease was not higher in the women with PCOS compared with the national mortality rates in women, although the observed proportion of women with diabetes as a contributory or underlying factor leading to death was significantly higher than expected (odds ratio 3.6,95% CI 1.5-8.4). Thus despite surrogate markers for cardiovascular disease, in this study, no increased rate of death from CVS disease could be demonstrated.
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