Endocrine Abstracts

Background: Insulin resistance (IR) commonly manifests in acromegaly leading to impaired glucose tolerance (IGT) and diabetes mellitus (DM). Studies have shown that ‘control’ of growth hormone (GH) and insulin-like growth factor 1 (IGF1) hypersecretion typically ameliorates glucose homeostasis. However, suppression of beta-cell function by somatostatin analogues may potentially attenuate glycaemic benefits of reduced IR. Effects on insulin’s other pleiotropic effects are not conclusive.

Aim: To assess the effects of Somatuline Autogel® (SA) on pancreatic beta-cell function, IR, and indices of tissue-specific insulin action in a cohort of newly diagnosed acromegalic patients.

Methods: Seventeen subjects (8 female, 9 male: mean age 55 years, range 26–73 year) were studied prior to, and following, 6 months of medical therapy with SA. Fasting glucose, insulin, HbA1c, free fatty acids (FFAs), adiponectin, leptin, retinol binding protein (RBP) and SHBG were determined. HOMA-IR and HOMA-beta indices were calculated.

Results: Following treatment GH and IGF1 levels fell significantly in all but one subject: median GH change −17.2 mU/l (interquartile range (IQR) −40.0 to −12.1, P=0.0024); median IGF1 change −49.9 nmol/l (IQR −90.4 to −27.2, P=0.0003).

Five patients had DM, three had IGT and one had impaired fasting glucose at baseline. Fasting insulin levels (median change −44 pmol/l, IQR −64 to −22, P<0.0001) and HOMA-IR (median change −0.8, IQR −1.3 to −0.3, P<0.0001) were improved by SA. A significant reduction in HOMA-beta (median change −24.3 IQR −53.1, −17.6, P<0.0001) was also found; however, no change in either HbA1c or fasting glucose levels was detected, suggesting that the net effect of SA on glucose homeostasis was benign.

There were no significant changes in lipid profile, leptin, adiponectin, RBP, SHBG, or FFAs.

Discussion: Six months of SA therapy successfully reduced GH/IGF1 levels in acromegaly, and led to marked insulin sensitization, which outweighed reduced beta-cell function. There were no changes in adipokine profile, lipids and SHBG.