Impaired beta-cell function in the presence of reduced insulin sensitivitydetermines glucose tolerance status in acromegalic patients

OBJECTIVE Abnormal glucose tolerance is often demonstrated in acromegalic p atients. Although insulin resistance is a common feature of acromegaly, it remains unclear whether the extent of insulin resistance per se determines the abnormal glucose tolerance. In order to elucidate this issue, we invest igated insulin sensitivity and beta-cell function in acromegalic patients. DESIGN Twenty-four acromegalic patients were studied in comparison with 24 healthy control subjects. To estimate insulin sensitivity and beta-cell fun ction, we used correct homeostasis model assessment (HOMA) model, a compute r-solved model. We also investigated the effects of surgical success on bot h parameters. RESULTS HOMA insulin sensitivity (HOMA-%S) in the acromegalic patients was 74 +/- 51 (SD)%, significantly lower than that in 24 healthy controls (144 +/- 49%), HOMA-%S in 12 normal glucose tolerance (NGT) patients was 54 +/- 31%, not significantly different from that in impaired glucose tolerance (I GT; n=11) or diabetes mellitus (DM; n=1) patients (93 +/- 60%), By contrast , HOMA beta-cell function (HOMA-%beta) in the NGT acromegalic patients was 163+/-67%, significantly higher than the IGT/DM acromegalic patients (89 +/ - 34%) and the healthy controls (72 +/- 19%), In 11 patients who achieved c omplete normalization of GH excess after surgery, HOMA-%S significantly inc reased to control ranges (from 76+/-26 to 159 +/- 61%) within 2 weeks after the surgical success. CONCLUSIONS We conclude that insulin sensitivity is reduced to a similar ex tent in acromegalic patients with normal glucose tolerance and those with i mpaired glucose tolerance or diabetes, Compensatory hyperfunction of B-cell s appears to counterbalance the reduced insulin sensitivity in the acromega lic patients with normal glucose tolerance but not in those with impaired g lucose tolerance or diabetes.