Abstract.With a euglycemic hyperinsulinemic clamp method, whole-body insulin resistance was assessed in 6 cases with acromegaly associated with diabetes mellitus before and after transsphenoidal adenomectomy.The glucose infusion rate (GIR) correlated well with the plasma IGF-I level but poorly with that of GH. Further improvement in insulin sensitivity occurred 3-4 months after operation without substantial changes in plasma levels of both GH and IGF-I or glycemic control. These results indicate that GH excess can induce insulin resistance in association with plasma IGF-1 and also through undefined secondary effect.
Wereport four non-insulin-dependent diabetic (NIDDM) patients accompanied by a unique combination of sick sinus syndrome (SSS) and hyperinsulinemia of unknown etiology. SSS of all four cases was due to sinus arrest in association with paroxysmal atrial fibrillation (Rubenstein-III). Of special interest is that one patient showed a high prevalence ofSSS and NIDDMamongher close relatives. Hyperinsulinemia of moderate degree was seen at fasting state or after carbohydrate ingestion in the absence of obesity. The resistance to the action of insulin on glucose metabolism which was evaluated in three patients by the euglycemic hyperinsulinemic clamp study wasfound to be comparable to the lowest quartile level for commonNIDDMpatients. Because insulin is a physiological regulator of cell-membrane Na+/K+-ATPase, wespeculate that malfunction of the sinus node automaticity may be caused by chronic exposure to hyperinsulinemia secondary to insulin resistance in these NIDDM patients.
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