The clinical relevance of fasting and postprandial hypoglycemia in patients with cystic fibrosis (CF) is poorly characterized. Our aim in this study was to characterize the prevalence of hypoglycemia in adult patients during oral glucose tolerance test (OGTT) screening and determine its impact on the risk of developing CF-related diabetes (CFRD).
We analyzed 2 cohorts of pancreatic insufficient patients with CF exposed to comparable treatment recommendations in France (Lyon CF cohort [DIAMUCO]) and Canada (Montréal CF cohort [MCFC]). Patients were classified into 3 groups based on hypoglycemia absence or presence as well as its severity at baseline. We defined the groups as follows: level 2 hypoglycemia (L2H; plasma glucose [PG]<3.0 mmol/L), level 1 hypoglycemia (L1H; PG 3.0 to <4.0 mmol/L) and no hypoglycemia (NH) during an OGTT.
A total of 153 MCFC and 114 DIAMUCO subjects were included in the study. In total, 22% of the patients experienced hypoglycemia, with 5% having it on 2 or more OGTTs. The L1H and L2H groups tended to have a lower 2-hour glucose and higher early-phase insulin secretion (insulin area under the curve at 0 to 30 minutes) compared with NH patients. In both cohorts, a greater proportion of men and patients with normal glucose tolerance had hypoglycemia. Over a 5-year period, there were no cases of CFRD in the L2H group, whereas 4 subjects in the L1H group and 36 in the NH group developed CFRD.
Patients with hypoglycemia were at lower risk of developing CFRD, but at higher risk of early-phase insulin secretion and unsuppressed insulin secretion. This could potentially lead to further hypoglycemia after the 2-hour OGTT, suggesting high clinical relevance.

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