Insulin resistance in acromegaly: evaluation by studies of insulin binding to erythrocytes

Insulin binding to erythrocytes (RBC) was evaluated in 10 acromegalic patients (6 females and 4 males) in comparison to 22 normal subjects (12 females and 10 males) in an attempt to study the insulin resistance of acromegaly. Basal glucose from all acromegalic patients were within the normal range but incremental glucose and insulin curves, respectively, on oGTT were significantly increased in the acromegalic patients suggesting an insulin resistant state. Basal growth hormone concentrations were elevated in all acromegalic patients, but no correlation was observed between insulin and GH levels. The insulin binding studies in the acromegalic patients showed a decreased binding due to a reduction in the receptor number per cell but with no alterations in the affinity state. Correction of data for creatine, as a procedure of normalization of binding data for a standardized RBC cell age, enhanced the reduction of insulin binding of the acromegalic patients in comparison to controls in consequence to the younger population of acromegalic RBC as indicated by their increased creatine concentrations. In conclusion, the insulin resistant state in acromegalics observed in our study is accompanied by a decrease in the insulin binding to the RBC receptor due to a reduction of the receptor concentration as mediated by the compensatory hyperinsulinemia.