PCOS is closely tied to insulin resistance. It occurs in 70-95% of obese women and 30-75% of lean women with PCOS. It is hypothesised that insulin resistance is one cause of PCOS, but what is insulin resistance and how does it disrupt ovulatory function?
"What is insulin resistance?"
Insulin is a very important hormone responsible for controlling your blood sugar levels. Insulin acts on liver, muscle and fat cells to take in glucose from the blood to produce energy after the intake of food.
However, insulin resistance is when these liver, muscle and fat cells do not respond well to insulin and can't easily take in glucose from the blood, causing "hyperglycaemia" (very high blood sugar levels). In turn, the pancreas has to work even harder to produce more insulin, referred to as "hyperinsulinemia" (very high blood insulin levels).
The common symptoms of insulin resistance include: extreme thirst or hunger, feeling hungry, increased urination, feeling tired, elevated blood sugar levels, frequent infections and tingly sensations in the hands or feet.
"What causes insulin resistance?"
There is not one specific cause of insulin resistance. However, obesity, an inactive lifestyle and a diet high in carbohydrates are primary causes of insulin resistance. This is alongside mild genetic influences.
Research has also suggested that glucose mediated chronic low-grade inflammation ("pro-inflammatory state") can cause insulin resistance in PCOS women. This is why some women find that ketogenic diets are beneficial at treating their PCOS.
Recent studies have presented that hyperinsulinemia caused by insulin resistance can disrupt ovulation. Therefore, targeting this root cause of ovulatory dysfunction via diet modifications and medication may reverse these symptoms of PCOS.
Additionally, research has shown that hyperinsulinemia can reduce sex hormone binding globulin (SHBG). SHBG is responsible for carrying testosterone in an inactive form. Therefore, less SHBG means that there is more active free testosterone, causing male characteristics.
"How does hyperinsulinemia disrupt ovulation in PCOS?"
Recent research studies have presented that insulin binds to insulin receptors on theca cells (the outer layer of ovarian follicles) to produce androgens (testosterone/androstenedione) to inhibit the development of follicles for ovulation. Therefore, the combination of LH and insulin synergistically increases androgen biosynthesis.
The insulin induced state called "hyperandrogenism" (very high testosterone levels) arrests follicle maturation to prevent ovulation.
To hopefully help you understand this, here is a graphical image of insulin acting on ovarian follicles with a zoom in on the ovarian theca cells.
"Does treatment for insulin resistance reverse ovulatory dysfunction?"
There are many insulin-sensitizing drugs to manage insulin mediated ovarian hyperandrogenism. These insulin-sensitizing drugs are often prescribed to patients with type 2 diabetes, such as: metformin and thiazolidinedione (TZD). These drugs help your body respond better to insulin.
However, it is very important to point out that stopping metformin therapy will lead to the symptoms of ovulatory dysfunction to return. Therefore, something important to address is diet. Consuming too many calories by excess fat, sugar and alcohol and physical activity influences insulin resistance. Many studies have shown that the efficacy of metformin therapy increases in combination to diet modifications.
You DO NOT need to go on medication to reverse your insulin resistance. If you want to do this naturally, there are certain dieting tips, supplements and exercise you can do. If you want to learn about these tips, stay tuned for my other blogs on this topic.
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