Insulin resistance indicates a situation where high insulin levels are needed to maintain normal blood glucose. It is a reflection of decreased insulin-dependent glucose utilization. Patients would have a high fasting insulin but normal fasting blood glucose levels. The glucose insulin ratio would be low. Both obese and lean women with PCOS are at greater risk of being insulin resistant than matched control groups with no PCOS. However it is a common finding in the general population depending on screening method, age and obesity. Its prevalence has been reported to be 2-3 times higher than that of PCOS.
Insulin resistance could progress into glucose intolerance and type 2 diabetes. With time insulin level might drop despite increased levels of glucose due to exhaustion of the pancreatic beta cells.
High insulin levels stimulate the ovaries to produce more male hormones and suppress the liver producing less SHBG which is the protein carrier molecule for male hormones. Accordingly a woman might have high free testosterone despite normal total androgen levels. This could lead to skin and other related symptoms and signs. A direct correlation has been shown between the degree of insulin resistance and anovulatory infertility.
Insulin also acts directly at the ovaries causing impaired steroidogenesis (normal production of steroid hormones) and limiting follicular growth. This could be mediated through increased protease inhibitor 'Plasminogen Activator Inhibitor PAI-1' and an imbalance in the production of insulin like growth factors.
Furthermore a direct action of insulin on the brain might increase LH secretion by the pituitary gland and stimulates appetite as well.
Weight reduction and exercise are the best measures to reduce the insulin level. This should be a sustained effort maintained through changes in life style rather than by starving oneself. Metformin is also used regularly for controlling insulin resistance. See management of PCOS.
The American College of Obstetrics and Gynaecology recommended that all patients with PCOS be tested for type II diabetes and glucose intolerance.
