Evaluation of serum insulin levels after an oral glucose load for the diagnosis of insulin resistance

• Published in: Revista medíca de Chile Vol. 142; no. 9; pp. 1106 - 1112
• Main Authors: Arancibia, Constanza, Galgani, José, Valderas, Juan P, Morales, Mauricio, Santos, José Luis, Pollak, Felipe
• Format: Journal Article
• Language: Spanish
• Published: Chile 01-09-2014
• Subjects: Adolescent; Adult; Aged; Female; Glucose Tolerance Test; Homeostasis; Humans; Hyperinsulinism - blood; Hyperinsulinism - diagnosis; Hyperinsulinism - physiopathology; Insulin - blood; Insulin Resistance; Male; Middle Aged; Postprandial Period; Retrospective Studies; Sensitivity and Specificity; Young Adult
• ISSN: 0717-6163
• DOI: 10.4067/S0034-98872014000900003

In our country, the assessment of insulin resistance (IR) measuring serum insulin levels at 60 and 120 minutes after a 75 g oral glucose tolerance test (OGTT), is usual. However, there is no information about the distribution of serum insulin levels in the Chilean population.
To assess the distribution of serum insulin levels at 60 and 120 minutes during OGTTs and suggest a statistical cut-off point to estimate the degree of IR.
Retrospective analysis of 1815 OGTTs performed in non-diabetic subjects aged between 18 and 75 years, at a university medical center. HOMA-IR (Homeostasis Model Assessment), insulin sensitivity index of Matsuda (ISI-Composite), and their correlation with serum insulin levels at 60 and 120 minutes were calculated.
The 75th percentiles for serum insulin levels at 60 and 120 minutes were 127 and 81 µU/mL, respectively. There was a high correlation between HOMA-IR and ISI-Composite (r = -089, p < 0.001). There was a weaker although significant correlation between HOMA-IR and ISI-Composite and insulin levels at 60 (r = 0.56 and -0.79 respectively, p < 0,001) and 120 minutes (r = 0.54 and -0.75 respectively, p < 0,001).
We propose 60 and 120 min serum insulin levels of 130 and 80 µU/mL respectively, as cut-off values for normality during OGTT in Chilean normoglycemic individuals.