Cover Story

Controlling PCOS Part 1

Assessing insulin sensitivity

By Robert P. Kauffman, MD, and V. Daniel Castracane, PhD

While experts continue to debate the exact causes of PCOS, there's little doubt that insulin resistance plays an important role in its pathophysiology. In the first installment of our series on PCOS, two authorities offer a detailed yet practical discussion on how to evaluate insulin sensitivity.

Most first-year medical students know that the inability of a patient's tissues to respond to insulin is the hallmark of Type 2 diabetes, a fact that came to light in 1938, and was later confirmed with development of an insulin immunoassay in 1960. It wasn't until 1980, however, that the relationship between insulin resistance and polycystic ovary syndrome (PCOS) was clearly established.^1-3

The sensitivity of cells to insulin is determined by the response of circulating glucose to endogenous or exogenous insulin. Insulin resistance is characterized by a diminished glucose response to the metabolic actions of the hormone, or expressed in another way, it's the inverse of insulin sensitivity.⁴ And although other metabolic and physiologic parameters like lipid metabolism, vascular endothelial function, and gene expression are partially regulated by insulin action, these parameters are not considered when assessing insulin sensitivity.⁴