FNDC5 and hyperinsulinism: They studied the effect of hyperinsulinemia on irisin levels with the hyperinsulinemic euglycemic glucose clamp: At the beginning of the assay, short-term hyperinsulinemia determined a rapid decrease of irisin concentrations in both groups, and therefore, during the steady state of the test, its levels were constant, suggesting that elevated irisin concentrations in PCOS patients may be a consequence of metabolic stress.