1286-P: Hyperinsulinemia Is Common in Individuals with Normoglycemia in a Nationwide Working-Age Population

Introduction: Hyperinsulinemia is associated with future diabetes and cardiovascular disease. However, fasting insulin (FI) levels are rarely assessed in individuals with normoglycemia. To investigate the potential magnitude of undiagnosed hyperinsulinemia (FI >16 uIU/mL), we assessed the prevalence of hyperinsulinemia in individuals with normoglycemia (fasting glucose [FG] 70 to <100 mg/dL) in a nation-wide study of working-age individuals without diabetes.

Methods: The study included employees and spouses who participated in an annual health assessment program at Quest Diagnostics (October 2020 to February 2021). Those with diabetes, with FG <70 or ≥100 mg/dL, or with missing data were excluded. FI was measured by a mass-spectrometry assay standardized for the peptide content of WHO reference materials.

Results: Participants included 23,339 individuals (68% women) with normoglycemia (FG ≥70 or <100 mg/dL) and median age of 43 years (IQR 34 to 53). Hyperinsulinemia was observed in 7% (n =1,546) of participants. Of these, 1,064 individuals also participated in the health assessment program in a subsequent year and 46% (n =490) of them had persistent hyperinsulinemia. Obesity (BMI ≥30 kg/m²) was more common (83% vs. 71%) in those with persistent hyperinsulinemia than in those without (P <0.001) and they had lower HDL-C levels (45 vs 47 mg/dL, P <0.001) Age, sex, and triglyceride levels did not differ between those with and without persistent hyperinsulinemia (all P >0.05). Of the 490 individuals with persistent hyperinsulinemia, 76% (n =373) had persistent normoglycemia.

Conclusion: In a large population of working-age individuals, hyperinsulinemia was found in about 1 in 15 individuals with normoglycemia. Those with persistent hyperinsulinemia in a subsequent year were more likely to have obesity and lower HDL-C levels, and about 1 in 5 were no longer normoglycemic. Measurement of FI levels may have value in even apparently metabolically normal individuals.