Four patients, treated with pentamidine because of Pneumocystis carinii pneumonitis, displayed severe fasting hypoglycemia during this treatment. Diabetes mellitus appeared later, requiring insulin therapy in the three of them who survived more than a few weeks.

The metabolic study, performed in two cases during the hypoglycemic period, demonstrated inappropriately high insulin levels in the postaborptive state. 28 ± 1 μU/ml (blood glucose 41 ± 4 mg/dl) and 86 ± 5 μU/ml (blood glucose 15 ± 5 mg/dl) vs. 15 ± 3 μU/ml in 10 control subjects and 55 ± 3 μU/ml in 6 patients with a verified B-cell tumor, respectively. Poor B-cell secretory responses followed the stimulations by oral glucose (maximal increment over basal: +5 μU/ml vs. +40 μU/ml in control group and +77 μU/ml in the insulinoma group), by i.v. arginine (maximal increment +10 and +28 μU/ml, respectively, vs. +55 in the controls and +90 μU/ml in the insulinoma group) and by i.v. glucagon (+10 and +23 μU/ml, respectively) vs. +40 μU/ml in both the control and the insulinoma groups). Plasma cortisol and glucagon, and the A-cell response to arginine were higher than normal.

These high, nonsuppressible, nonstimulable insulin levels and the sequence of hypoglycemia followed by insulin-dependent diabetes mellitus is consistent with the hypothesis of a selective toxicity turned towards the B-cells. In vitro incubation of islets with pentamidine 10−10 M produced a passive release of insulin, followed by a significant decrease in B-cell response to glucose + theophylline. It is suggested that pentamidine can induce hypoglycemia because of an early cytolytic release of insulin, and then diabetes mellitus because of B-cell destruction and insulin deficiency.

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