Context: Idiopathic reactive hypoglycemia (IRH) is characterized by recurrent episodes of symptomatic hypoglycemia occurring within 4 hours after meals. The underlying mechanisms remain obscure.
Objective: This study aimed to investigate the response of the glucoregulatory and gastrointestinal hormones to an oral glucose load (OGTT) in individuals with documented IRH.
Design and setting: This was a cross-sectional study composed of outpatients referred to "Federico II" University of Naples.
Patients: We enrolled subjects with IRH documented by a mixed meal under ordinary life conditions and healthy subjects as controls.
Main outcome measure: We measured plasma glucose, insulin, glucagon-like peptide 1 (GLP-1), GIP, and glucagon response to a 75-g OGTT in cases and controls.
Results: Ten IRH and eight control subjects were enrolled. During the OGTT, mean plasma glucose tended to be lower in IRH than in control subjects, reaching a statistically significant difference at 240 minutes (T240) (43 ± 1.6 vs 72 ± 0.3 mg/dL; P = .001). Accordingly, the insulin response was higher in IRH than in control subjects (P < .019) with a statistically significant difference (46%) at T90 (P = .045) and was associated with significantly lower glucagon levels in the late phase of the OGTT: at T120 (P = .031) and T180 (P = .048) in IRH than in control subjects. A greater GLP-1 response was found among IRH compared with control subjects (P = .005); GLP-1 peak was 2-fold higher in IRH individuals (9.77 ± 2.52 pmol/L) than in the control group (4.19 ± 0.53 pmol/L; P = .041). In the IRH group, GLP-1 peak inversely correlated with the nadir of plasma glucose (r = -0.66; P = .039). A multivariate analysis confirmed that GLP-1 peak independently predicted the plasma glucose nadir (β = -0.593; P = .026).
Conclusions: GLP-1 may play a significant role in the pathogenesis of idiopathic IRH.