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The Association of Fasting Insulin Concentrations and Colonic Neoplasms in Acromegaly: A Colonoscopy-Based Study in 210 Patients

Department of Molecular and Clinical Endocrinology and Oncology (A.C., R.P., R.S.A., M.G., G.L.), Section of Endocrinology, University "Federico II" of Naples, 80131 Naples, Italy; Department of Endocrine and Metabolic Sciences and Center of Excellence for Biomedical Research (D.F., F.M.), University of Genova, 5-16126 Genova, Italy; and Division of General Medicine (P.M.), Ospedale San Giuseppe, Istituto Auxologico Italiano, 28921 Verbania, Italy

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

Context: Hyperinsulinemia is associated with colon carcinoma in the general population. Patients with acromegaly are considered to be at risk for developing colonic lesions and typically have hyperinsulinemia.

Objective: Our objective was to evaluate the role of fasting insulin levels on the prevalence of colonic adenomatous polyps or adenocarcinoma in acromegaly.

Design: This is an analytical, observational, prospective study.

Patients: A total of 210 patients (111 women, 99 men, age 20–82 yr) undergoing complete colonoscopy at diagnosis of acromegaly were included in this study.

Results: Colonic lesions were found in 81 patients (38.6%), and consisted of hyperplastic polyps in 33 (15.7%), adenomatous polyps in 42 (20.0%), and adenocarcinoma in six patients (2.8%). Polyps were single in 22 cases (27.1%). Fasting insulin levels were significantly lower in patients without lesions (16.0 ± 7.5 mU/liter) than in patients with hyperplastic polyps (22.4 ± 8.8 mU/liter; P < 0.01), adenomatous polyps (38.0 ± 15.9 mU/liter; P < 0.0001), and adenocarcinoma (59.0 ± 30.6 mU/liter; P < 0.0001). Fasting insulin levels were also lower in patients with hyperplastic polyps than in those with adenomatous polyps (P < 0.01). The odds ratio for harboring colonic adenomas was 14.8 (95% confidence interval 4.4–51.2; P < 0.0001) and 8.6 times higher (95% confidence interval 2.8–29.0; P < 0.0001) in patients with fasting insulin levels in the upper tertile [27.1 mIU/liter (n = 28)] compared with the lower [12.1 mIU/liter (n = 40)] and middle tertiles [>12.1 to <27.1 mIU/liter (n = 74)], respectively.

Conclusion: An increase in fasting insulin levels is associated with an 8.6- to 14.8-fold increased risk of presenting with colonic adenomas in acromegaly.