Insulin resistance and hyperinsulinemia: you can't have one without the other

Recently, it has been suggested that insulin resistance and hyperinsulinemia can exist in isolation and have differential impacts on cardiovascular disease (CVD). To evaluate this suggestion, we assessed the degree of discordance between insulin sensitivity and insulin response in a healthy, nondiabetic population.

Insulin sensitivity was quantified by determining the steady-state plasma glucose (SSPG) concentration during an insulin suppression test in 446 individuals. The integrated insulin response was calculated after a 75-g oral glucose challenge. We analyzed the correlation between insulin resistance and insulin response in addition to quantifying the proportion in quartiles of insulin response by quartiles of insulin sensitivity. Then we compared CVD risk factors between individuals within the same insulin sensitivity quartile but within different insulin response quartiles to evaluate the differential clinical impact of insulin resistance and hyperinsulinemia.

Insulin resistance and insulin response were highly correlated (r = 0.76, P < 0.001). A majority (95%) of the most insulin-resistant individuals (top SSPG quartile) were either in the highest insulin response quartile (71%) or second highest (24%). Similarly, 92% of the most insulin-sensitive individuals (lowest SSPG quartile) were in the lowest two insulin response quartiles. There were minimal differences in CVD risk factors between individuals with different insulin responses but within the same insulin sensitivity quartile.

Although not perfectly related, insulin resistance and hyperinsulinemia rarely exist in isolation in a nondiabetic population. It is difficult to discern an independent impact of hyperinsulinemia on CVD risk factors associated with insulin resistance.