Insulin sensitivity and pancreatic ß-cell function in patients with primary aldosteronism.

ABSTRACT

BACKGROUND: Primary aldosteronism (PA) is associated with an increased risk for dysglycemia. However, the effects of hyperaldosteronism on insulin sensitivity and ß-cell function are unclear. METHODS: Using a cross-sectional study design, we assessed insulin sensitivity and pancreatic ß-cell function from an oral glucose tolerance test (OGTT) in patients from two cohorts subjects with PA (n = 21) and essential hypertension control (EHC) subjects (n = 22). Age, sex, BMI, and mean arterial pressure adjusted measures of insulin sensitivity and ß-cell function were compared between the groups. RESULTS: PA individuals were less insulin sensitive compared to EHC subjects (Quantitative insulin sensitivity check index [QUICKI] 0.340 ± 0.006 vs. 0.374 ± 0.013, p < 0.001; Matsuda index 4.14 ± 0.49 vs. 7.87 ± 1.42, p < 0.001; SI 11.45 ± 4.85 vs. 21.23 ± 6.11 dL/kg/min per µU/mL, p = 0.02). The hepatic insulin resistance index (HIRI) was higher in PA subjects (PA 5.61 ± 1.01 vs. EHC 4.13 ± 0.61, p = 0.002). The insulinogenic index (IGI), an index of ß-cell function was higher in the PA cohort (PA 1.49 ± 0.27 vs. 1.11 ± 0.21 µU/mL/mg/dL, p = 0.03). However, the oral disposition index (DI) was similar between the groups (PA 4.77 ± 0.73 vs. EHC 5.46 ± 0.85, p = 0.42), which likely accounts for the similar glucose tolerance between the two cohorts, despite lower sensitivity. CONCLUSIONS: In summary, insulin sensitivity is significantly lower in PA with an appropriately compensated ß-cell function. These results suggest that excess aldosterone and/or other steroids in the context of PA may negatively affect insulin action without adversely impacting ß-cell function.