Anti-insulin antibodies are a cause of hypoglycemia following pancreas transplantation.

Abstract

Hypoglycemic symptoms have been reported by more than half of pancreas transplantation (PTX) recipients. To better understand the mechanism for the hypoglycemia documented in some of these patients, we studied the glucose and pancreatic hormone response to Sustacal in patients with and without hypoglycemia following PTX. Twelve patients with established, repeated episodes of hypoglycemia following PTX (hypo) were case-matched to PTX recipients without hypoglycemic symptoms (control; n = 7). On the day of the study, fasting glucose, free and total immunoreactive insulin (IRI), C-peptide, proinsulin, and glucagon were drawn (time 0); Sustacal was administered; and glucose, free and total IRI, and C-peptide were assayed at 15, 30, 45, 75, 120, 150, 180, and 240 min. Based on the glucose response to Sustacal, the hypo group was further divided into those whose glucose rose after Sustacal (hypo-high; n = 7) and those with no increase in glucose from baseline concentration (hypo-flat; n = 5). Before the administration of Sustacal, the hypo-high group had a lower fasting free/total IRI (0.26 +/- 0.06, mean +/- SE) than the hypo-flat (0.51 +/- 0.02) or control (0.52 +/- 0.04) groups (both P < 0.05 compared with hypo-high). The glucose response to Sustacal was greatest in the hypo-high group as defined. Area under the curve (AUC) for total IRI following Sustacal was also greatest in the hypo-high group (P < 0.05 compared with both control and hypo-flat groups), but there was no significant difference in free IRI AUC following Sustacal between the three groups. Two individuals developed hypoglycemia during the Sustacal challenge, both in the hypo-high group. The lower fasting free/total IRI ratio and greater increase in glucose and total IRI in response to Sustacal in the hypo-high group compared with either the hypo-flat or control groups are consistent with the presence of significant quantities of anti-insulin antibodies in the hypo-high group. Because anti-insulin antibodies are, in turn, an established cause of episodic hypoglycemia, this study provides the first data to support the hypothesis that significant quantities of anti-insulin antibodies are a cause of symptomatic hypoglycemia following PTX in some recipients.