It’s a common question: “Why have I been put on metformin if I have lean PCOS and don’t have insulin resistance?” This question highlights two important points:
1️⃣ Insulin resistance (IR) can occur in all body types. 2️⃣ Current tests for IR are not perfect.
Understanding Insulin Resistance and PCOS
In IR, cells become resistant to insulin, prompting the pancreas to produce more insulin to maintain normal blood glucose levels. Elevated insulin can disrupt the communication between the hypothalamus and the pituitary gland, affecting the ovary and leading to PCOS. Some individuals are highly sensitive to even mild IR, which might not be detected by standard tests, yet they still develop PCOS.
To diagnose IR, we typically use tests like the oral glucose tolerance test, fasting glucose, or HbA1c. Other helpful markers include sex-hormone binding globulin (which decreases) and triglycerides (which increase). However, the gold standard for measuring IR is the insulin clamp test. This test involves infusing a steady dose of insulin and adjusting glucose infusion to maintain stable blood glucose levels. The more insulin-sensitive a person is, the more glucose is required. This test is highly accurate but time-consuming and mainly used in research settings.
Insulin Resistance in Lean PCOS
A systematic review of insulin clamp tests in PCOS found that individuals with PCOS are 2.5 times more likely to have IR compared to those with the same BMI but without PCOS. Specifically, 75% of patients with lean PCOS and 95% with obesity-related PCOS had IR. This indicates that many women with PCOS have IR even if it’s not detected by standard tests.
Metformin and PCOS
Metformin has been shown to restore ovulation in women with PCOS. A small but well-conducted study involving 20 women with lean PCOS treated with 1700mg of metformin daily for six months found that 45% (9 out of 20) had restored ovulation, despite only one having IR diagnosed by fasting glucose and insulin levels. Several other studies have also demonstrated metformin’s effectiveness in restoring ovulation in PCOS.
Take-Home Message
Many women with PCOS likely have mild IR even if it’s not diagnosed through standard testing. Metformin has been shown to restore ovulation and decrease testosterone levels in PCOS, even in the absence of a formal IR diagnosis. If you have concerns or questions about your treatment, it’s always a good idea to discuss them with your healthcare provider. 😊