Effects of two different somatostatin analogs on glucose tolerance in acromegaly

Impaired glucose tolerance is present in many acromegalic patients and treatment with somatostatin analogs has variable effects on glycemic control. The aim of this study was to compare the effects of 2 somatostatin analogs on glucose metabolism, lanreotide slow release (L-SR) and octreotide long acting release (O-LAR), in 10 patients with acromegaly (2 of whom with overt Type 2 diabetes mellitus). Glucose and insulin levels in fasting conditions and in response to OGTT, evaluated as AUC, insulin resistance (IR) evaluated by homeostatic model assessment (HOMA-IR), glycosylated hemoglobin (HbA 1c ), GH, IGF-I, were assessed during L-SR and O-LAR treatment. Mean fasting glucose, glucose response to OGTT and HbA 1c levels in 8 non-diabetic patients did not significantly change after L-SR therapy while they all increased after O-LAR treatment ( p <0.05 vs baseline and L-SR). Mean HOMA-IR values calculated in acromegalic patients before medical therapy were higher than in normal subjects ( p <0.005) and showed a significant decrease during both treatments ( p <0.05). In the 2 diabetic acromegalic patients a worsening in glucose metabolism was observed during O-LAR treatment but not during L-SR. GH and IGF-I levels significantly decreased with both drugs and normalized respectively in 38% and 12% with L-SR, 50% and 25% with O-LAR. In conclusion, both drugs decreased IR in acromegalic patients; O-LAR seems to be more detrimental to glucose metabolism than L-SR, despite being more effective in reducing GH and IGF-I levels.