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Glucose Tolerance and Somatostatin Analog Treatment in Acromegaly: A 12-Month Study

Department of Molecular and Clinical Endocrinology and Oncology, section of Endocrinology, University Federico II of Naples, 80131 Naples, Italy

Address all correspondence and requests for reprints to: Annamaria Colao, M.D., Ph.D., Department of Molecular and Clinical Endocrinology and Oncology, Federico II University of Naples, via S. Pansini 5, 80131 Naples, Italy. E-mail: colao{at}unina.it.

Objective: The objective of the study was to investigate the impact of first-line somatostatin analogs (SSAs) on glucose tolerance (GT) in acromegaly.

Design: The design was open and prospective.

Patients: One hundred twelve patients [63 with normal GT (56.2%), 24 with impaired GT (21.4%), and 25 with diabetes (22.3%)] were treated with depot SSAs for 12 months: 54 patients (48.2%) achieved mean fasting GH levels less than 2.5 µg/liter in presence of normal IGF-I levels (controlled) during SSA.

Primary Outcome Measures: Fasting glucose and glycosylated hemoglobin levels were measured.

Results: At study end, 57 patients had normal GT (50.1% vs. baseline; P = 0.55), 30 had impaired fasting glucose or impaired GT (26.8%, P =0.43) and 25 had diabetes (22.3%; P = 1.0). Twenty-eight patients (25.0%), modified their GT [11 improved (9.8%), 17 worsened (15.2%)]: 90% of the patients with GT improvement achieved control of acromegaly and 89% of those having GT worsening did not (P < 0.0001). The major predictors of GT changing were disease control (t = –4.99; P < 0.0001), baseline GT (t = –2.84; P = 0.0054), and GH levels (t = 2.70; P = 0.008). Fasting glucose levels were predicted by patients’ age (t = 2.74; P = 0.0071) and IGF-I levels (t = 2.14; P = 0.035). Glycosylated hemoglobin levels were predicted by disease duration (t = 3.53; P = 0.0006), GH levels (t = 2.70; P = 0.0071), and IGF-I levels (t = 2.11; P = 0.037).

Conclusions: This study showed a similar prevalence of deterioration and improvement of GT 12 months after first-line SSA treatment. Uncontrolled acromegaly during SSA treatment and abnormal GT at baseline were associated with GT worsening.