Effect of treatment with somatostatin analogue on glucose homeostasis in patients with acromegaly
Nikos Gavalas, Andrea Sabo, Lida Papastathopoulou, Efi Botoula & Marinella Tzanela
Long acting somatostatin analogues (SMS) are extensively used as second and even first line treatment of acromegaly. Except of the inhibition of GH secretion, somatostatin is a potent inhibitor of insulin secretion from the pancreatic b- cells. As defects of glucose homeostasis are very common in acromegaly, we decided to examine the effect of the control of GH hypersecretion with SMS on glucose metabolism.
We study 44 acromegalic patients divided in 3 groups. Patients of group I (n=18) were evaluated at the time of diagnosis and before any therapeutic intervention, while patients of groups II and III were evaluated after control of their disease (indicated by normal IGF-I values for age and sex and GH levels <1 μg/L during OGTT, Consensus 2000) either by transphenoidal surgery, alone or followed by pituitary irradiation, (group II, n=16) or by somatostatin analogue administration (group III, n=10).
Insulin levels were significantly lower in groups II and III compared to group I (7.5±0.6 and 5.2±0.8 vs 15.7±2.7 μIU/ml, P<0.05) with a parallel drop of insulin resistance (as estimated by HOMA-IR) from 4.9±0.9 in group I to 1.8±0.2 and 1.4±0.2 (P<0.05) in groups II and III respectively. Insulin secretion (as estimated by HOMA-β) was statistically lower in group III than in group I and II (42.4±6.97 vs 117.2±18.8 and 85.6±7.49 respectively, P<0.05). These alterations led to lower mean glucose levels in group II compared group I (99±4.9 vs 120.9±8.3 mg/dl, P<0.05) but not in group III (108.4±3.1 mg/dl). The incidence of Diabetes Mellitus dropped from 50% in group I to 12% in group II and 10% in group III, while that of Impaired Glucose Tolerance from 33% in group I to 18.7% in group II but to 30% in group III.
In conclusion, despite of treatment modality, successful control of acromegaly reduces the incidence of Diabetes Mellitus. However, control of GH hypersecretion with SMS treatment seems to be less effective to fully reverse the impaired glucose tolerance, probably due to inhibition of insulin secretion by SMS.