Effects of the long-acting somatostatin analogue Lanreotide Autogel on glucose tolerance and insulin resistance in acromegaly

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Treatment with somatostatin analogues (SA) not only inhibits GH secretion but may also impair insulin secretion. In order to evaluate the influence of SA on glucose metabolism, we investigated insulin resistance (IR) and beta-cell function, using the recommended combination of homeostatic model assessment of IR (HOMA-IR) and beta-cell function (HOMA-beta). This is a prospective, cross-sectional study. We measured fasting insulin, blood glucose and IGF-I. Insulin and blood glucose measurements were taken 120 min after an oral glucose tolerance test with 75 g glucose. We studied 51 patients (27 female/24 male, age 54 years (20-75)). Eighteen patients were on Lanreotide Autogel (LA) treatment, 33 had no medical treatment. GH-levels of more than 2.5 ng/ml was reached by 59% of the patients, 74.5% had normal IGF-I levels. We found no significant influence of disease activity on HOMA-IR and HOMA-beta. In the 33 of 51 subjects without any drug treatment, median HOMA-beta was 170.4% (36.0-624.0%). In contrast, in the 18 patients on LA treatment, median HOMA-beta was found to be significantly lower (84.2% (36.5-346.2%); P = 0.001). Despite this, there was no difference in HOMA-IR in both groups (2.4 (0.7-8.4) vs 2.3 (0.7-6.1); P < 0.001) despite similar insulin values. In conclusion, we found that LA decreases beta-cell function significantly without affecting IR. Therefore, we think that insulin secretagogues are probably more effective in the treatment of diabetes mellitus in acromegalic patients on LA therapy than insulin sensitizers.